[PATCH v8 0/8] PCI: Add PCIe bandwidth controller

[PATCH v8 0/8] PCI: Add PCIe bandwidth controller

[Ilpo Järvinen]

Hi all,

This series adds PCIe bandwidth controller (bwctrl) and associated PCIe
cooling driver to the thermal core side for limiting PCIe Link Speed
due to thermal reasons. PCIe bandwidth controller is a PCI express bus
port service driver. A cooling device is created for each port the
service driver finds to support changing speeds.

This series only adds support for controlling PCIe Link Speed.
Controlling PCIe Link Width might also be useful but there is no
mechanism for that until PCIe 6.0 (L0p) so Link Width throttling is not
added by this series.

v8 makes bwctrl always enabled if PCIEPORTBUS is enabled (suggested by
Rafael J. Wysocki in VFIO/IOMMU/PCI MC at Vienna). This avoid lots of
complexity caused by the Kconfig variations. It also ensures the
current Link Speed is kept updated if the Link Speed is changing due to
reasons unrelated to the BW controller (a feature the mainline
currently lacks entirely since the BW notifications revert).

v8:
- Removed CONFIG_PCIE_BWCTRL (use CONFIG_PCIEPORTBUS)
- Removed locking wrappers that dealt with the CONFIG variations
- Protect macro parameter with parenthesis to be on the safe side

v7:
- Rebased on top of Maciej's latest Target Speed quirk patches
- Target Speed quirk runs very early, w/o ->subordinate existing yet.
  This required adapting logic:
	- Move Supported Link Speeds back to pci_dev
	- Check for ->subordinate == NULL where necessary
	- Cannot always take bwctrl's per port mutex (in pcie_bwctrl_data)
- Cleaned up locking in pcie_set_target_speed() using wrappers
	- Allowed removing confusing __pcie_set_target_speed()
- Fix building with CONFIG_PCI=n
- Correct error check in pcie_lbms_seen()
- Don't return error for an empty bus that remains at 2.5GT
- Use rwsem to protect ->link_bwctrl setup and bwnotif enable
- Clear LBMS in remove_board()
- Adding export for pcie_get_supported_speeds() was unnecessary
- Call bwctrl's init before hotplug.
- Added local variable 'bus' into a few functions

v6:
- Removed unnecessary PCI_EXP_LNKCAP_SLS mask from PCIE_LNKCAP_SLS2SPEED()
- Split error handling in pcie_bwnotif_irq_thread()
- pci_info() -> pci_dbg() on bwctrl probe success path
- Handle cooling device pointer -Exx codes in bwctrl probe
- Reorder port->link_bwctrl setup / bwnotif enable for symmetry
- Handle LBMS count == 0 in PCIe quirk by checking LBMS (avoids a race
  between quirk and bwctrl)
- Use cleanup.h in PCIe cooling device's register

v5:
- Removed patches: LNKCTL2 RMW driver patches went in separately
- Refactor pcie_update_link_speed() to read LNKSTA + add __ variant
  for hotplug that has LNKSTA value at hand
- Make series fully compatible with the Target Speed quirk
	- LBMS counter added, quirk falls back to LBMS bit when bwctrl =n
	- Separate LBMS patch from set target speed patches
- Always provide pcie_bwctrl_change_speed() even if bwctrl =n so drivers
  don't need to come up their own version (also required by the Target
  Speed quirk)
- Remove devm_* (based on Lukas' comment on some other service
  driver patch)
- Convert to use cleanup.h
- Renamed functions/struct to have shorter names

v4:
- Merge Port's and Endpoint's Supported Link Speeds Vectors into
  supported_speeds in the struct pci_bus
- Reuse pcie_get_speed_cap()'s code for pcie_get_supported_speeds()
- Setup supported_speeds with PCI_EXP_LNKCAP2_SLS_2_5GB when no
  Endpoint exists
- Squash revert + add bwctrl patches into one
- Change to use threaded IRQ + IRQF_ONESHOT
- Enable also LABIE / LABS
- Convert Link Speed selection to use bit logic instead of loop
- Allocate before requesting IRQ during probe
- Use devm_*()
- Use u8 for speed_conv array instead of u16
- Removed READ_ONCE()
- Improve changelogs, comments, and Kconfig
- Name functions slightly more consistently
- Use bullet list for RMW protected registers in docs

v3:
- Correct hfi1 shortlog prefix
- Improve error prints in hfi1
- Add L: linux-pci to the MAINTAINERS entry

v2:
- Adds LNKCTL2 to RMW safe list in Documentation/PCI/pciebus-howto.rst
- Renamed cooling devices from PCIe_Port_* to PCIe_Port_Link_Speed_* in
  order to plan for possibility of adding Link Width cooling devices
  later on
- Moved struct thermal_cooling_device declaration to the correct patch
- Small tweaks to Kconfig texts
- Series rebased to resolve conflict (in the selftest list)

Ilpo Järvinen (8):
  PCI: Protect Link Control 2 Register with RMW locking
  PCI: Store all PCIe Supported Link Speeds
  PCI: Refactor pcie_update_link_speed()
  PCI/quirks: Abstract LBMS seen check into own function
  PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller
  PCI/bwctrl: Add API to set PCIe Link Speed
  thermal: Add PCIe cooling driver
  selftests/pcie_bwctrl: Create selftests

 Documentation/PCI/pciebus-howto.rst           |  14 +-
 MAINTAINERS                                   |   9 +
 drivers/pci/hotplug/pciehp_ctrl.c             |   5 +
 drivers/pci/hotplug/pciehp_hpc.c              |   2 +-
 drivers/pci/pci.c                             |  60 ++-
 drivers/pci/pci.h                             |  38 +-
 drivers/pci/pcie/Makefile                     |   2 +-
 drivers/pci/pcie/bwctrl.c                     | 358 ++++++++++++++++++
 drivers/pci/pcie/portdrv.c                    |   9 +-
 drivers/pci/pcie/portdrv.h                    |   6 +-
 drivers/pci/probe.c                           |  15 +-
 drivers/pci/quirks.c                          |  32 +-
 drivers/thermal/Kconfig                       |   9 +
 drivers/thermal/Makefile                      |   2 +
 drivers/thermal/pcie_cooling.c                |  80 ++++
 include/linux/pci-bwctrl.h                    |  28 ++
 include/linux/pci.h                           |  24 +-
 include/uapi/linux/pci_regs.h                 |   1 +
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/pcie_bwctrl/Makefile  |   2 +
 .../pcie_bwctrl/set_pcie_cooling_state.sh     | 122 ++++++
 .../selftests/pcie_bwctrl/set_pcie_speed.sh   |  67 ++++
 22 files changed, 832 insertions(+), 54 deletions(-)
 create mode 100644 drivers/pci/pcie/bwctrl.c
 create mode 100644 drivers/thermal/pcie_cooling.c
 create mode 100644 include/linux/pci-bwctrl.h
 create mode 100644 tools/testing/selftests/pcie_bwctrl/Makefile
 create mode 100755 tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh
 create mode 100755 tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh

-- 
2.39.5

[PATCH v8 1/8] PCI: Protect Link Control 2 Register with RMW locking

[Ilpo Järvinen]

PCIe Bandwidth Controller performs RMW accesses the Link Control 2
Register which can occur concurrently to other sources of Link Control
2 Register writes. Therefore, add Link Control 2 Register among the PCI
Express Capability Registers that need RMW locking.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
---
 Documentation/PCI/pciebus-howto.rst | 14 +++++++++-----
 include/linux/pci.h                 |  1 +
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Documentation/PCI/pciebus-howto.rst b/Documentation/PCI/pciebus-howto.rst
index f344452651e1..375d9ce171f6 100644
--- a/Documentation/PCI/pciebus-howto.rst
+++ b/Documentation/PCI/pciebus-howto.rst
@@ -217,8 +217,12 @@ capability structure except the PCI Express capability structure,
 that is shared between many drivers including the service drivers.
 RMW Capability accessors (pcie_capability_clear_and_set_word(),
 pcie_capability_set_word(), and pcie_capability_clear_word()) protect
-a selected set of PCI Express Capability Registers (Link Control
-Register and Root Control Register). Any change to those registers
-should be performed using RMW accessors to avoid problems due to
-concurrent updates. For the up-to-date list of protected registers,
-see pcie_capability_clear_and_set_word().
+a selected set of PCI Express Capability Registers:
+
+* Link Control Register
+* Root Control Register
+* Link Control 2 Register
+
+Any change to those registers should be performed using RMW accessors to
+avoid problems due to concurrent updates. For the up-to-date list of
+protected registers, see pcie_capability_clear_and_set_word().
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 573b4c4c2be6..be5ed534c39c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1274,6 +1274,7 @@ static inline int pcie_capability_clear_and_set_word(struct pci_dev *dev,
 {
 	switch (pos) {
 	case PCI_EXP_LNKCTL:
+	case PCI_EXP_LNKCTL2:
 	case PCI_EXP_RTCTL:
 		return pcie_capability_clear_and_set_word_locked(dev, pos,
 								 clear, set);
-- 
2.39.5

Re: [PATCH v8 1/8] PCI: Protect Link Control 2 Register with RMW locking

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:16 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> PCIe Bandwidth Controller performs RMW accesses the Link Control 2
> Register which can occur concurrently to other sources of Link Control
> 2 Register writes. Therefore, add Link Control 2 Register among the PCI
> Express Capability Registers that need RMW locking.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Reviewed-by: Lukas Wunner <lukas@wunner.de>
Totally trivial comment inline.

LGTM

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  Documentation/PCI/pciebus-howto.rst | 14 +++++++++-----
>  include/linux/pci.h                 |  1 +
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/PCI/pciebus-howto.rst b/Documentation/PCI/pciebus-howto.rst
> index f344452651e1..375d9ce171f6 100644
> --- a/Documentation/PCI/pciebus-howto.rst
> +++ b/Documentation/PCI/pciebus-howto.rst
> @@ -217,8 +217,12 @@ capability structure except the PCI Express capability structure,
>  that is shared between many drivers including the service drivers.
>  RMW Capability accessors (pcie_capability_clear_and_set_word(),
>  pcie_capability_set_word(), and pcie_capability_clear_word()) protect
> -a selected set of PCI Express Capability Registers (Link Control
> -Register and Root Control Register). Any change to those registers
> -should be performed using RMW accessors to avoid problems due to
> -concurrent updates. For the up-to-date list of protected registers,
> -see pcie_capability_clear_and_set_word().
> +a selected set of PCI Express Capability Registers:
> +
> +* Link Control Register
> +* Root Control Register
> +* Link Control 2 Register
> +
> +Any change to those registers should be performed using RMW accessors to
> +avoid problems due to concurrent updates. For the up-to-date list of
> +protected registers, see pcie_capability_clear_and_set_word().

If I were super fussy I'd ask for a precursor patch doing the reformat.

Meh - up to Bjorn, but for me this is small enough to not be worth
the effort.

> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 573b4c4c2be6..be5ed534c39c 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1274,6 +1274,7 @@ static inline int pcie_capability_clear_and_set_word(struct pci_dev *dev,
>  {
>  	switch (pos) {
>  	case PCI_EXP_LNKCTL:
> +	case PCI_EXP_LNKCTL2:
>  	case PCI_EXP_RTCTL:
>  		return pcie_capability_clear_and_set_word_locked(dev, pos,
>  								 clear, set);

Re: [PATCH v8 1/8] PCI: Protect Link Control 2 Register with RMW locking

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 2958 bytes --]

On Thu, 17 Oct 2024, Jonathan Cameron wrote:

> On Wed,  9 Oct 2024 12:52:16 +0300
> Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> 
> > PCIe Bandwidth Controller performs RMW accesses the Link Control 2
> > Register which can occur concurrently to other sources of Link Control
> > 2 Register writes. Therefore, add Link Control 2 Register among the PCI
> > Express Capability Registers that need RMW locking.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > Reviewed-by: Lukas Wunner <lukas@wunner.de>
> Totally trivial comment inline.
> 
> LGTM
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> > ---
> >  Documentation/PCI/pciebus-howto.rst | 14 +++++++++-----
> >  include/linux/pci.h                 |  1 +
> >  2 files changed, 10 insertions(+), 5 deletions(-)
> > 
> > diff --git a/Documentation/PCI/pciebus-howto.rst b/Documentation/PCI/pciebus-howto.rst
> > index f344452651e1..375d9ce171f6 100644
> > --- a/Documentation/PCI/pciebus-howto.rst
> > +++ b/Documentation/PCI/pciebus-howto.rst
> > @@ -217,8 +217,12 @@ capability structure except the PCI Express capability structure,
> >  that is shared between many drivers including the service drivers.
> >  RMW Capability accessors (pcie_capability_clear_and_set_word(),
> >  pcie_capability_set_word(), and pcie_capability_clear_word()) protect
> > -a selected set of PCI Express Capability Registers (Link Control
> > -Register and Root Control Register). Any change to those registers
> > -should be performed using RMW accessors to avoid problems due to
> > -concurrent updates. For the up-to-date list of protected registers,
> > -see pcie_capability_clear_and_set_word().
> > +a selected set of PCI Express Capability Registers:
> > +
> > +* Link Control Register
> > +* Root Control Register
> > +* Link Control 2 Register
> > +
> > +Any change to those registers should be performed using RMW accessors to
> > +avoid problems due to concurrent updates. For the up-to-date list of
> > +protected registers, see pcie_capability_clear_and_set_word().
> 
> If I were super fussy I'd ask for a precursor patch doing the reformat.
> 
> Meh - up to Bjorn, but for me this is small enough to not be worth
> the effort.

Hi Jonathan,

Thanks. Since you brought it up, I've no problem in splitting the 
reformatting into own patch, it won't take more than a minute
anyway to do that change.

-- 
 i.

> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 573b4c4c2be6..be5ed534c39c 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1274,6 +1274,7 @@ static inline int pcie_capability_clear_and_set_word(struct pci_dev *dev,
> >  {
> >  	switch (pos) {
> >  	case PCI_EXP_LNKCTL:
> > +	case PCI_EXP_LNKCTL2:
> >  	case PCI_EXP_RTCTL:
> >  		return pcie_capability_clear_and_set_word_locked(dev, pos,
> >  								 clear, set);
> 
> 

[PATCH v8 2/8] PCI: Store all PCIe Supported Link Speeds

[Ilpo Järvinen]

PCIe bandwidth controller added by a subsequent commit will require
selecting PCIe Link Speeds that are lower than the Maximum Link Speed.

The struct pci_bus only stores max_bus_speed. Even if PCIe r6.1 sec
8.2.1 currently disallows gaps in supported Link Speeds, the
Implementation Note in PCIe r6.1 sec 7.5.3.18, recommends determining
supported Link Speeds using the Supported Link Speeds Vector in the
Link Capabilities 2 Register (when available) to "avoid software being
confused if a future specification defines Links that do not require
support for all slower speeds."

Reuse code in pcie_get_speed_cap() to add pcie_get_supported_speeds()
to query the Supported Link Speeds Vector of a PCIe device. The value
is taken directly from the Supported Link Speeds Vector or synthetized
from the Max Link Speed in the Link Capabilities Register when the Link
Capabilities 2 Register is not available.

The Supported Link Speeds Vector in the Link Capabilities Register 2
corresponds to the bus below on Root Ports and Downstream Ports,
whereas it corresponds to the bus above on Upstream Ports and
Endpoints (PCIe r6.1 sec 7.5.3.18):

	"Supported Link Speeds Vector - This field indicates the
	supported Link speed(s) of the associated Port."

Add supported_speeds into the struct pci_dev that caches the
Supported Link Speeds Vector.

supported_speeds contains a set of Link Speeds only in the case where
PCIe Link Speed can be determined. The Root Complex Integrated
Endpoints do not have a well-defined Link Speed because they do not
seem to implement either of the Link Capabilities Registers, which is
allowed by PCIe r6.1 sec 7.5.3 (the same limitation applies to
determining cur_bus_speed and max_bus_speed that are PCI_SPEED_UNKNOWN
in such case). This is of no concern from PCIe bandwidth controller
point of view because such devices are not attached into a PCIe Root
Port that could be controlled.

supported_speeds field keeps the extra reserved zero at the least
significant bit to match the Link Capabilities 2 Register layouting.

An attempt was made to store supported_speeds field into the struct
pci_bus as an intersection of the both ends of the Link, however, the
subordinate struct pci_bus is not available early enough. The Target
Speed quirk (in pcie_failed_link_retrain()) can run either during
initial scan or later requiring it to use the API PCIe bandwidth
controller provides to set the Target Link Speed in order to co-exist
with the bandwidth controller. When the Target Speed quirk is calling
the bandwidth controller during initial scan, the struct pci_bus is not
yet initialized. As such, storing supported_speeds into the struct
pci_bus is not viable.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/pci.c             | 58 ++++++++++++++++++++++++-----------
 drivers/pci/probe.c           |  3 ++
 include/linux/pci.h           | 11 ++++++-
 include/uapi/linux/pci_regs.h |  1 +
 4 files changed, 54 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7d85c04fbba2..b28ab4761b18 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6189,38 +6189,60 @@ u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev,
 EXPORT_SYMBOL(pcie_bandwidth_available);
 
 /**
- * pcie_get_speed_cap - query for the PCI device's link speed capability
+ * pcie_get_supported_speeds - query Supported Link Speed Vector
  * @dev: PCI device to query
  *
- * Query the PCI device speed capability.  Return the maximum link speed
- * supported by the device.
+ * Query @dev supported link speeds.
+ *
+ * Implementation Note in PCIe r6.0.1 sec 7.5.3.18 recommends determining
+ * supported link speeds using the Supported Link Speeds Vector in the Link
+ * Capabilities 2 Register (when available).
+ *
+ * Link Capabilities 2 was added in PCIe r3.0, sec 7.8.18.
+ *
+ * Without Link Capabilities 2, i.e., prior to PCIe r3.0, Supported Link
+ * Speeds field in Link Capabilities is used and only 2.5 GT/s and 5.0 GT/s
+ * speeds were defined.
+ *
+ * For @dev without Supported Link Speed Vector, the field is synthetized
+ * from the Max Link Speed field in the Link Capabilities Register.
+ *
+ * Return: Supported Link Speeds Vector
  */
-enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
+u8 pcie_get_supported_speeds(struct pci_dev *dev)
 {
 	u32 lnkcap2, lnkcap;
+	u8 speeds;
 
-	/*
-	 * Link Capabilities 2 was added in PCIe r3.0, sec 7.8.18.  The
-	 * implementation note there recommends using the Supported Link
-	 * Speeds Vector in Link Capabilities 2 when supported.
-	 *
-	 * Without Link Capabilities 2, i.e., prior to PCIe r3.0, software
-	 * should use the Supported Link Speeds field in Link Capabilities,
-	 * where only 2.5 GT/s and 5.0 GT/s speeds were defined.
-	 */
 	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
+	speeds = lnkcap2 & PCI_EXP_LNKCAP2_SLS;
 
 	/* PCIe r3.0-compliant */
-	if (lnkcap2)
-		return PCIE_LNKCAP2_SLS2SPEED(lnkcap2);
+	if (speeds)
+		return speeds;
 
 	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+
+	/* Synthetize from the Max Link Speed field */
 	if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_5_0GB)
-		return PCIE_SPEED_5_0GT;
+		speeds = PCI_EXP_LNKCAP2_SLS_5_0GB | PCI_EXP_LNKCAP2_SLS_2_5GB;
 	else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
-		return PCIE_SPEED_2_5GT;
+		speeds = PCI_EXP_LNKCAP2_SLS_2_5GB;
+
+	return speeds;
+}
 
-	return PCI_SPEED_UNKNOWN;
+/**
+ * pcie_get_speed_cap - query for the PCI device's link speed capability
+ * @dev: PCI device to query
+ *
+ * Query the PCI device speed capability.
+ *
+ * Return: the maximum link speed supported by the device.
+ */
+enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
+{
+	return PCIE_LNKCAP2_SLS2SPEED(dev->supported_speeds);
 }
 EXPORT_SYMBOL(pcie_get_speed_cap);
 
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 4f68414c3086..af153a8e8225 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1947,6 +1947,9 @@ int pci_setup_device(struct pci_dev *dev)
 
 	set_pcie_untrusted(dev);
 
+	if (pci_is_pcie(dev))
+		dev->supported_speeds = pcie_get_supported_speeds(dev);
+
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index be5ed534c39c..a02b77fe7865 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -303,6 +303,7 @@ enum pci_bus_speed {
 	PCI_SPEED_UNKNOWN		= 0xff,
 };
 
+u8 pcie_get_supported_speeds(struct pci_dev *dev);
 enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev);
 enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev);
 
@@ -318,7 +319,14 @@ struct pci_sriov;
 struct pci_p2pdma;
 struct rcec_ea;
 
-/* The pci_dev structure describes PCI devices */
+/* struct pci_dev - describes a PCI device
+ *
+ * @supported_speeds:	PCIe Supported Link Speeds Vector (+ reserved 0 at
+ *			LSB). 0 when the supported speeds cannot be
+ *			determined (e.g., for Root Complex Integrated
+ *			Endpoints without the relevant Capability
+ *			Registers).
+ */
 struct pci_dev {
 	struct list_head bus_list;	/* Node in per-bus list */
 	struct pci_bus	*bus;		/* Bus this device is on */
@@ -522,6 +530,7 @@ struct pci_dev {
 	struct npem	*npem;		/* Native PCIe Enclosure Management */
 #endif
 	u16		acs_cap;	/* ACS Capability offset */
+	u8		supported_speeds; /* Supported Link Speeds Vector */
 	phys_addr_t	rom;		/* Physical address if not from BAR */
 	size_t		romlen;		/* Length if not from BAR */
 	/*
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 12323b3334a9..f3c9de0a497c 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -678,6 +678,7 @@
 #define PCI_EXP_DEVSTA2		0x2a	/* Device Status 2 */
 #define PCI_CAP_EXP_RC_ENDPOINT_SIZEOF_V2 0x2c	/* end of v2 EPs w/o link */
 #define PCI_EXP_LNKCAP2		0x2c	/* Link Capabilities 2 */
+#define  PCI_EXP_LNKCAP2_SLS		0x000000fe /* Supported Link Speeds Vector */
 #define  PCI_EXP_LNKCAP2_SLS_2_5GB	0x00000002 /* Supported Speed 2.5GT/s */
 #define  PCI_EXP_LNKCAP2_SLS_5_0GB	0x00000004 /* Supported Speed 5GT/s */
 #define  PCI_EXP_LNKCAP2_SLS_8_0GB	0x00000008 /* Supported Speed 8GT/s */
-- 
2.39.5

Re: [PATCH v8 2/8] PCI: Store all PCIe Supported Link Speeds

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:17 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:


> 
> supported_speeds field keeps the extra reserved zero at the least
> significant bit to match the Link Capabilities 2 Register layouting.
layout.

> 
> An attempt was made to store supported_speeds field into the struct
> pci_bus as an intersection of the both ends of the Link, however, the
> subordinate struct pci_bus is not available early enough. The Target
> Speed quirk (in pcie_failed_link_retrain()) can run either during
> initial scan or later requiring it to use the API PCIe bandwidth
> controller provides to set the Target Link Speed in order to co-exist
> with the bandwidth controller. When the Target Speed quirk is calling
> the bandwidth controller during initial scan, the struct pci_bus is not
> yet initialized. As such, storing supported_speeds into the struct
> pci_bus is not viable.

Excellent detailed description!

> 
> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
One trivial request inline.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/pci/pci.c             | 58 ++++++++++++++++++++++++-----------
>  drivers/pci/probe.c           |  3 ++
>  include/linux/pci.h           | 11 ++++++-
>  include/uapi/linux/pci_regs.h |  1 +
>  4 files changed, 54 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d85c04fbba2..b28ab4761b18 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c

> -enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
> +u8 pcie_get_supported_speeds(struct pci_dev *dev)
>  {
>  	u32 lnkcap2, lnkcap;
> +	u8 speeds;
>  
> -	/*
> -	 * Link Capabilities 2 was added in PCIe r3.0, sec 7.8.18.  The
> -	 * implementation note there recommends using the Supported Link
> -	 * Speeds Vector in Link Capabilities 2 when supported.
> -	 *
> -	 * Without Link Capabilities 2, i.e., prior to PCIe r3.0, software
> -	 * should use the Supported Link Speeds field in Link Capabilities,
> -	 * where only 2.5 GT/s and 5.0 GT/s speeds were defined.
> -	 */
>  	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
> +	speeds = lnkcap2 & PCI_EXP_LNKCAP2_SLS;

I'd be tempted to leave a breadcrumb here in the form of a comment
to stop the obviously 'correct' but totally wrong FIELD_GET()
being used to replace this because of that LSB 0.
You have it well commented elsewhere but anyone editing this
code might not look at where it is written to.

(I'd written that feedback before realizing my error ;)
>  

[PATCH v8 3/8] PCI: Refactor pcie_update_link_speed()

[Ilpo Järvinen]

pcie_update_link_speed() is passed the Link Status register but not all
callers have that value at hand nor need the value.

Refactor pcie_update_link_speed() to include reading the Link Status
register and create __pcie_update_link_speed() which can be used by the
hotplug code that has the register value at hand beforehand (and needs
the value for other purposes).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/hotplug/pciehp_hpc.c |  2 +-
 drivers/pci/pci.h                |  7 ++++++-
 drivers/pci/probe.c              | 12 +++++++-----
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 736ad8baa2a5..bb5a8d9f03ad 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -319,7 +319,7 @@ int pciehp_check_link_status(struct controller *ctrl)
 		return -1;
 	}
 
-	pcie_update_link_speed(ctrl->pcie->port->subordinate, lnk_status);
+	__pcie_update_link_speed(ctrl->pcie->port->subordinate, lnk_status);
 
 	if (!found) {
 		ctrl_info(ctrl, "Slot(%s): No device found\n",
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 14d00ce45bfa..6e827d47aa85 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -378,7 +378,12 @@ enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev);
 enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev);
 void __pcie_print_link_status(struct pci_dev *dev, bool verbose);
 void pcie_report_downtraining(struct pci_dev *dev);
-void pcie_update_link_speed(struct pci_bus *bus, u16 link_status);
+
+static inline void __pcie_update_link_speed(struct pci_bus *bus, u16 linksta)
+{
+	bus->cur_bus_speed = pcie_link_speed[linksta & PCI_EXP_LNKSTA_CLS];
+}
+void pcie_update_link_speed(struct pci_bus *bus);
 
 /* Single Root I/O Virtualization */
 struct pci_sriov {
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index af153a8e8225..c138daf78961 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -742,9 +742,13 @@ const char *pci_speed_string(enum pci_bus_speed speed)
 }
 EXPORT_SYMBOL_GPL(pci_speed_string);
 
-void pcie_update_link_speed(struct pci_bus *bus, u16 linksta)
+void pcie_update_link_speed(struct pci_bus *bus)
 {
-	bus->cur_bus_speed = pcie_link_speed[linksta & PCI_EXP_LNKSTA_CLS];
+	struct pci_dev *bridge = bus->self;
+	u16 linksta;
+
+	pcie_capability_read_word(bridge, PCI_EXP_LNKSTA, &linksta);
+	__pcie_update_link_speed(bus, linksta);
 }
 EXPORT_SYMBOL_GPL(pcie_update_link_speed);
 
@@ -827,13 +831,11 @@ static void pci_set_bus_speed(struct pci_bus *bus)
 
 	if (pci_is_pcie(bridge)) {
 		u32 linkcap;
-		u16 linksta;
 
 		pcie_capability_read_dword(bridge, PCI_EXP_LNKCAP, &linkcap);
 		bus->max_bus_speed = pcie_link_speed[linkcap & PCI_EXP_LNKCAP_SLS];
 
-		pcie_capability_read_word(bridge, PCI_EXP_LNKSTA, &linksta);
-		pcie_update_link_speed(bus, linksta);
+		pcie_update_link_speed(bus);
 	}
 }
 
-- 
2.39.5

Re: [PATCH v8 3/8] PCI: Refactor pcie_update_link_speed()

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:18 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> pcie_update_link_speed() is passed the Link Status register but not all
> callers have that value at hand nor need the value.
> 
> Refactor pcie_update_link_speed() to include reading the Link Status
> register and create __pcie_update_link_speed() which can be used by the
> hotplug code that has the register value at hand beforehand (and needs
> the value for other purposes).
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

[PATCH v8 4/8] PCI/quirks: Abstract LBMS seen check into own function

[Ilpo Järvinen]

The Target Speed quirk in pcie_failed_link_retrain() uses the presence
of LBMS bit as one of the triggering conditions effectively
monopolizing the use of that bit. An upcoming change will introduce a
PCIe bandwidth controller which sets up an interrupt to track LBMS. As
LBMS will be cleared by the interrupt handler, the Target Speed quirk
will no longer be able to observe LBMS directly.

As a preparatory step for the change, extract the LBMS seen check into
own function out of pcie_failed_link_retrain().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/quirks.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index dccb60c1d9cc..a560ea403b8e 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -33,6 +33,11 @@
 #include <linux/switchtec.h>
 #include "pci.h"
 
+static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
+{
+	return lnksta & PCI_EXP_LNKSTA_LBMS;
+}
+
 /*
  * Retrain the link of a downstream PCIe port by hand if necessary.
  *
@@ -96,8 +101,7 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &lnkctl2);
 	pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
-	if ((lnksta & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_DLLLA)) ==
-	    PCI_EXP_LNKSTA_LBMS) {
+	if (!(lnksta & PCI_EXP_LNKSTA_DLLLA) && pcie_lbms_seen(dev, lnksta)) {
 		u16 oldlnkctl2 = lnkctl2;
 
 		pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
-- 
2.39.5

Re: [PATCH v8 4/8] PCI/quirks: Abstract LBMS seen check into own function

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:19 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> The Target Speed quirk in pcie_failed_link_retrain() uses the presence
> of LBMS bit as one of the triggering conditions effectively
> monopolizing the use of that bit. An upcoming change will introduce a
> PCIe bandwidth controller which sets up an interrupt to track LBMS. As
> LBMS will be cleared by the interrupt handler, the Target Speed quirk
> will no longer be able to observe LBMS directly.
> 
> As a preparatory step for the change, extract the LBMS seen check into
> own function out of pcie_failed_link_retrain().
extract the LBMS seen check from pcie_failed_link_retrain() into
a new function pcie_lmbs_seen()

perhaps is slightly clearer?
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

[PATCH v8 5/8] PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller

[Ilpo Järvinen]

This mostly reverts the commit b4c7d2076b4e ("PCI/LINK: Remove
bandwidth notification"). An upcoming commit extends this driver
building PCIe bandwidth controller on top of it.

The PCIe bandwidth notification were first added in the commit
e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth
notification") but later had to be removed. The significant changes
compared with the old bandwidth notification driver include:

1) Don't print the notifications into kernel log, just keep the Link
   Speed cached into the struct pci_bus updated. While somewhat
   unfortunate, the log spam was the source of complaints that
   eventually lead to the removal of the bandwidth notifications driver
   (see the links below for further information).

2) Besides the Link Bandwidth Management Interrupt, enable also Link
   Autonomous Bandwidth Interrupt to cover the other source of
   bandwidth changes.

3) Use threaded IRQ with IRQF_ONESHOT to handle Bandwidth Notification
   Interrupts to address the problem fixed in the commit 3e82a7f9031f
   ("PCI/LINK: Supply IRQ handler so level-triggered IRQs are acked")).

4) Handle Link Speed updates robustly. Refresh the cached Link Speed
   when enabling Bandwidth Notification Interrupts, and solve the race
   between Link Speed read and LBMS/LABS update in
   pcie_bwnotif_irq_thread().

5) Use concurrency safe LNKCTL RMW operations.

6) The driver is now called PCIe bwctrl (bandwidth controller) instead
   of just bandwidth notifications because of increased scope and
   functionality within the driver.

7) Coexist with the Target Link Speed quirk in
   pcie_failed_link_retrain(). Provide LBMS counting API for it.

8) Tweaks to variable/functions names for consistency and length
   reasons.

Bandwidth Notifications enable the cur_bus_speed in the struct pci_bus
to keep track PCIe Link Speed changes.

Link: https://lore.kernel.org/all/20190429185611.121751-1-helgaas@kernel.org/
Link: https://lore.kernel.org/linux-pci/20190501142942.26972-1-keith.busch@intel.com/
Link: https://lore.kernel.org/linux-pci/20200115221008.GA191037@google.com/
Suggested-by: Lukas Wunner <lukas@wunner.de> # Building bwctrl on top of bwnotif
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 MAINTAINERS                       |   6 +
 drivers/pci/hotplug/pciehp_ctrl.c |   5 +
 drivers/pci/pci.c                 |   2 +-
 drivers/pci/pci.h                 |  11 ++
 drivers/pci/pcie/Makefile         |   2 +-
 drivers/pci/pcie/bwctrl.c         | 190 ++++++++++++++++++++++++++++++
 drivers/pci/pcie/portdrv.c        |   9 +-
 drivers/pci/pcie/portdrv.h        |   6 +-
 drivers/pci/quirks.c              |   9 +-
 include/linux/pci.h               |   2 +
 10 files changed, 233 insertions(+), 9 deletions(-)
 create mode 100644 drivers/pci/pcie/bwctrl.c

diff --git a/MAINTAINERS b/MAINTAINERS
index c27f3190737f..8c555b3325d6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17933,6 +17933,12 @@ F:	include/linux/of_pci.h
 F:	include/linux/pci*
 F:	include/uapi/linux/pci*
 
+PCIE BANDWIDTH CONTROLLER
+M:	Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
+L:	linux-pci@vger.kernel.org
+S:	Supported
+F:	drivers/pci/pcie/bwctrl.c
+
 PCIE DRIVER FOR AMAZON ANNAPURNA LABS
 M:	Jonathan Chocron <jonnyc@amazon.com>
 L:	linux-pci@vger.kernel.org
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index dcdbfcf404dd..d603a7aa7483 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -19,6 +19,8 @@
 #include <linux/types.h>
 #include <linux/pm_runtime.h>
 #include <linux/pci.h>
+
+#include "../pci.h"
 #include "pciehp.h"
 
 /* The following routines constitute the bulk of the
@@ -127,6 +129,9 @@ static void remove_board(struct controller *ctrl, bool safe_removal)
 
 	pciehp_set_indicators(ctrl, PCI_EXP_SLTCTL_PWR_IND_OFF,
 			      INDICATOR_NOOP);
+
+	/* Don't carry LBMS indications across */
+	pcie_reset_lbms_count(ctrl->pcie->port);
 }
 
 static int pciehp_enable_slot(struct controller *ctrl);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b28ab4761b18..c1f9616485ae 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4740,7 +4740,7 @@ int pcie_retrain_link(struct pci_dev *pdev, bool use_lt)
 	 * to track link speed or width changes made by hardware itself
 	 * in attempt to correct unreliable link operation.
 	 */
-	pcie_capability_write_word(pdev, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS);
+	pcie_reset_lbms_count(pdev);
 	return rc;
 }
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 6e827d47aa85..33ed324d1953 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -697,6 +697,17 @@ static inline void pcie_set_ecrc_checking(struct pci_dev *dev) { }
 static inline void pcie_ecrc_get_policy(char *str) { }
 #endif
 
+#ifdef CONFIG_PCIEPORTBUS
+void pcie_reset_lbms_count(struct pci_dev *port);
+int pcie_lbms_count(struct pci_dev *port, unsigned long *val);
+#else
+static inline void pcie_reset_lbms_count(struct pci_dev *port) {}
+static inline int pcie_lbms_count(struct pci_dev *port, unsigned long *val)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 struct pci_dev_reset_methods {
 	u16 vendor;
 	u16 device;
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 6461aa93fe76..53ccab62314d 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -4,7 +4,7 @@
 
 pcieportdrv-y			:= portdrv.o rcec.o
 
-obj-$(CONFIG_PCIEPORTBUS)	+= pcieportdrv.o
+obj-$(CONFIG_PCIEPORTBUS)	+= pcieportdrv.o bwctrl.o
 
 obj-y				+= aspm.o
 obj-$(CONFIG_PCIEAER)		+= aer.o err.o
diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
new file mode 100644
index 000000000000..1b11b5da79d4
--- /dev/null
+++ b/drivers/pci/pcie/bwctrl.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PCIe bandwidth controller
+ *
+ * Author: Alexandru Gagniuc <mr.nuke.me@gmail.com>
+ *
+ * Copyright (C) 2019 Dell Inc
+ * Copyright (C) 2023-2024 Intel Corporation
+ *
+ * This service port driver hooks into the Bandwidth Notification interrupt
+ * watching for changes or links becoming degraded in operation. It updates
+ * the cached Current Link Speed that is exposed to user space through sysfs.
+ */
+
+#define dev_fmt(fmt) "bwctrl: " fmt
+
+#include <linux/atomic.h>
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/pci.h>
+#include <linux/rwsem.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "../pci.h"
+#include "portdrv.h"
+
+/**
+ * struct pcie_bwctrl_data - PCIe bandwidth controller
+ * @lbms_count:		Count for LBMS (since last reset)
+ */
+struct pcie_bwctrl_data {
+	atomic_t lbms_count;
+};
+
+/* Prevents port removal during link speed changes and LBMS count accessors */
+static DECLARE_RWSEM(pcie_bwctrl_remove_rwsem);
+
+static void pcie_bwnotif_enable(struct pcie_device *srv)
+{
+	struct pcie_bwctrl_data *data = get_service_data(srv);
+	struct pci_dev *port = srv->port;
+	u16 link_status;
+	int ret;
+
+	/* Count LBMS seen so far as one */
+	ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
+	if (ret == PCIBIOS_SUCCESSFUL && link_status & PCI_EXP_LNKSTA_LBMS)
+		atomic_inc(&data->lbms_count);
+
+	pcie_capability_set_word(port, PCI_EXP_LNKCTL,
+				 PCI_EXP_LNKCTL_LBMIE | PCI_EXP_LNKCTL_LABIE);
+	pcie_capability_write_word(port, PCI_EXP_LNKSTA,
+				   PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_LABS);
+
+	/*
+	 * Update after enabling notifications & clearing status bits ensures
+	 * link speed is up to date.
+	 */
+	pcie_update_link_speed(port->subordinate);
+}
+
+static void pcie_bwnotif_disable(struct pci_dev *port)
+{
+	pcie_capability_clear_word(port, PCI_EXP_LNKCTL,
+				   PCI_EXP_LNKCTL_LBMIE | PCI_EXP_LNKCTL_LABIE);
+}
+
+static irqreturn_t pcie_bwnotif_irq_thread(int irq, void *context)
+{
+	struct pcie_device *srv = context;
+	struct pcie_bwctrl_data *data = get_service_data(srv);
+	struct pci_dev *port = srv->port;
+	u16 link_status, events;
+	int ret;
+
+	ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
+	if (ret != PCIBIOS_SUCCESSFUL)
+		return IRQ_NONE;
+
+	events = link_status & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_LABS);
+	if (!events)
+		return IRQ_NONE;
+
+	if (events & PCI_EXP_LNKSTA_LBMS)
+		atomic_inc(&data->lbms_count);
+
+	pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
+
+	/*
+	 * Interrupts will not be triggered from any further Link Speed
+	 * change until LBMS is cleared by the write. Therefore, re-read the
+	 * speed (inside pcie_update_link_speed()) after LBMS has been
+	 * cleared to avoid missing link speed changes.
+	 */
+	pcie_update_link_speed(port->subordinate);
+
+	return IRQ_HANDLED;
+}
+
+void pcie_reset_lbms_count(struct pci_dev *port)
+{
+	struct pcie_bwctrl_data *data;
+
+	guard(rwsem_read)(&pcie_bwctrl_remove_rwsem);
+	data = port->link_bwctrl;
+	if (data)
+		atomic_set(&data->lbms_count, 0);
+	else
+		pcie_capability_write_word(port, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS);
+}
+
+int pcie_lbms_count(struct pci_dev *port, unsigned long *val)
+{
+	struct pcie_bwctrl_data *data;
+
+	guard(rwsem_read)(&pcie_bwctrl_remove_rwsem);
+	data = port->link_bwctrl;
+	if (!data)
+		return -ENOTTY;
+
+	*val = atomic_read(&data->lbms_count);
+
+	return 0;
+}
+
+static int pcie_bwnotif_probe(struct pcie_device *srv)
+{
+	struct pci_dev *port = srv->port;
+	int ret;
+
+	struct pcie_bwctrl_data *data __free(kfree) =
+				kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	set_service_data(srv, data);
+
+	ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
+				   IRQF_SHARED | IRQF_ONESHOT, "PCIe bwctrl", srv);
+	if (ret)
+		return ret;
+
+	port->link_bwctrl = no_free_ptr(data);
+	pcie_bwnotif_enable(srv);
+
+	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
+
+	return 0;
+}
+
+static void pcie_bwnotif_remove(struct pcie_device *srv)
+{
+	struct pcie_bwctrl_data *data = get_service_data(srv);
+
+	pcie_bwnotif_disable(srv->port);
+	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem)
+		srv->port->link_bwctrl = NULL;
+
+	free_irq(srv->irq, srv);
+	kfree(data);
+}
+
+static int pcie_bwnotif_suspend(struct pcie_device *srv)
+{
+	pcie_bwnotif_disable(srv->port);
+	return 0;
+}
+
+static int pcie_bwnotif_resume(struct pcie_device *srv)
+{
+	pcie_bwnotif_enable(srv);
+	return 0;
+}
+
+static struct pcie_port_service_driver pcie_bwctrl_driver = {
+	.name		= "pcie_bwctrl",
+	.port_type	= PCIE_ANY_PORT,
+	.service	= PCIE_PORT_SERVICE_BWCTRL,
+	.probe		= pcie_bwnotif_probe,
+	.suspend	= pcie_bwnotif_suspend,
+	.resume		= pcie_bwnotif_resume,
+	.remove		= pcie_bwnotif_remove,
+};
+
+int __init pcie_bwctrl_init(void)
+{
+	return pcie_port_service_register(&pcie_bwctrl_driver);
+}
diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
index 6af5e0425872..5e10306b6308 100644
--- a/drivers/pci/pcie/portdrv.c
+++ b/drivers/pci/pcie/portdrv.c
@@ -68,7 +68,7 @@ static int pcie_message_numbers(struct pci_dev *dev, int mask,
 	 */
 
 	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP |
-		    PCIE_PORT_SERVICE_BWNOTIF)) {
+		    PCIE_PORT_SERVICE_BWCTRL)) {
 		pcie_capability_read_word(dev, PCI_EXP_FLAGS, &reg16);
 		*pme = FIELD_GET(PCI_EXP_FLAGS_IRQ, reg16);
 		nvec = *pme + 1;
@@ -150,11 +150,11 @@ static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 
 	/* PME, hotplug and bandwidth notification share an MSI/MSI-X vector */
 	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP |
-		    PCIE_PORT_SERVICE_BWNOTIF)) {
+		    PCIE_PORT_SERVICE_BWCTRL)) {
 		pcie_irq = pci_irq_vector(dev, pme);
 		irqs[PCIE_PORT_SERVICE_PME_SHIFT] = pcie_irq;
 		irqs[PCIE_PORT_SERVICE_HP_SHIFT] = pcie_irq;
-		irqs[PCIE_PORT_SERVICE_BWNOTIF_SHIFT] = pcie_irq;
+		irqs[PCIE_PORT_SERVICE_BWCTRL_SHIFT] = pcie_irq;
 	}
 
 	if (mask & PCIE_PORT_SERVICE_AER)
@@ -271,7 +271,7 @@ static int get_port_device_capability(struct pci_dev *dev)
 
 		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &linkcap);
 		if (linkcap & PCI_EXP_LNKCAP_LBNC)
-			services |= PCIE_PORT_SERVICE_BWNOTIF;
+			services |= PCIE_PORT_SERVICE_BWCTRL;
 	}
 
 	return services;
@@ -828,6 +828,7 @@ static void __init pcie_init_services(void)
 	pcie_aer_init();
 	pcie_pme_init();
 	pcie_dpc_init();
+	pcie_bwctrl_init();
 	pcie_hp_init();
 }
 
diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
index 12c89ea0313b..bd29d1cc7b8b 100644
--- a/drivers/pci/pcie/portdrv.h
+++ b/drivers/pci/pcie/portdrv.h
@@ -20,8 +20,8 @@
 #define PCIE_PORT_SERVICE_HP		(1 << PCIE_PORT_SERVICE_HP_SHIFT)
 #define PCIE_PORT_SERVICE_DPC_SHIFT	3	/* Downstream Port Containment */
 #define PCIE_PORT_SERVICE_DPC		(1 << PCIE_PORT_SERVICE_DPC_SHIFT)
-#define PCIE_PORT_SERVICE_BWNOTIF_SHIFT	4	/* Bandwidth notification */
-#define PCIE_PORT_SERVICE_BWNOTIF	(1 << PCIE_PORT_SERVICE_BWNOTIF_SHIFT)
+#define PCIE_PORT_SERVICE_BWCTRL_SHIFT	4	/* Bandwidth Controller (notifications) */
+#define PCIE_PORT_SERVICE_BWCTRL	(1 << PCIE_PORT_SERVICE_BWCTRL_SHIFT)
 
 #define PCIE_PORT_DEVICE_MAXSERVICES   5
 
@@ -51,6 +51,8 @@ int pcie_dpc_init(void);
 static inline int pcie_dpc_init(void) { return 0; }
 #endif
 
+int pcie_bwctrl_init(void);
+
 /* Port Type */
 #define PCIE_ANY_PORT			(~0)
 
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index a560ea403b8e..e6d502dca939 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -35,7 +35,14 @@
 
 static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
 {
-	return lnksta & PCI_EXP_LNKSTA_LBMS;
+	unsigned long count;
+	int ret;
+
+	ret = pcie_lbms_count(dev, &count);
+	if (ret < 0)
+		return lnksta & PCI_EXP_LNKSTA_LBMS;
+
+	return count > 0;
 }
 
 /*
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a02b77fe7865..5f9de226be13 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -314,6 +314,7 @@ struct pci_vpd {
 };
 
 struct irq_affinity;
+struct pcie_bwctrl_data;
 struct pcie_link_state;
 struct pci_sriov;
 struct pci_p2pdma;
@@ -503,6 +504,7 @@ struct pci_dev {
 	unsigned int	dpc_rp_extensions:1;
 	u8		dpc_rp_log_size;
 #endif
+	struct pcie_bwctrl_data		*link_bwctrl;
 #ifdef CONFIG_PCI_ATS
 	union {
 		struct pci_sriov	*sriov;		/* PF: SR-IOV info */
-- 
2.39.5

Re: [PATCH v8 5/8] PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:20 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> This mostly reverts the commit b4c7d2076b4e ("PCI/LINK: Remove
> bandwidth notification"). An upcoming commit extends this driver
> building PCIe bandwidth controller on top of it.
> 
> The PCIe bandwidth notification were first added in the commit
> e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth
> notification") but later had to be removed. The significant changes
> compared with the old bandwidth notification driver include:
> 
> 1) Don't print the notifications into kernel log, just keep the Link
>    Speed cached into the struct pci_bus updated. While somewhat

cached in struct pci_bus updated.

>    unfortunate, the log spam was the source of complaints that
>    eventually lead to the removal of the bandwidth notifications driver
>    (see the links below for further information).
> 
> Link: https://lore.kernel.org/all/20190429185611.121751-1-helgaas@kernel.org/
> Link: https://lore.kernel.org/linux-pci/20190501142942.26972-1-keith.busch@intel.com/
> Link: https://lore.kernel.org/linux-pci/20200115221008.GA191037@google.com/
> Suggested-by: Lukas Wunner <lukas@wunner.de> # Building bwctrl on top of bwnotif
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

A couple of comments inline, but they are things that I plan
to tackle for other service drivers as part of the first stage
of the rework discussed at LPC.

I don't mind just including patches for this code in there
it you'd prefer to minimize changes at this point.

Jonathan

> +static int pcie_bwnotif_probe(struct pcie_device *srv)
> +{
> +	struct pci_dev *port = srv->port;
> +	int ret;
> +
> +	struct pcie_bwctrl_data *data __free(kfree) =
> +				kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	set_service_data(srv, data);
> +
> +	ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
> +				   IRQF_SHARED | IRQF_ONESHOT, "PCIe bwctrl", srv);
> +	if (ret)
> +		return ret;
> +
> +	port->link_bwctrl = no_free_ptr(data);
> +	pcie_bwnotif_enable(srv);
> +
> +	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
> +
> +	return 0;
> +}
> +
> +static void pcie_bwnotif_remove(struct pcie_device *srv)
> +{
> +	struct pcie_bwctrl_data *data = get_service_data(srv);

this is the same as srv->port->link_bwctrl I think
Can we kill of the service data use?  That's one of the early
changes I have in cleaning up portdrv in general.  Aim
is to make it all look much more like you have here with
explicit pointers in port.

If not I'll just sweep that up in the same cleanup set.
(I'm hoping this merges soon to make that exercise easier!)

> +
> +	pcie_bwnotif_disable(srv->port);
> +	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem)
> +		srv->port->link_bwctrl = NULL;
> +
> +	free_irq(srv->irq, srv);
> +	kfree(data);

Also on that cleanup plan is using devm_ for all this
stuff in the portdrv service drivers (squashing them
into one driver at the same time).
Maybe worth doing at least the data and irq handling now
but I'm also fine just rolling it into that mega exercise.


> +}

[PATCH v8 6/8] PCI/bwctrl: Add API to set PCIe Link Speed

[Ilpo Järvinen]

Currently, PCIe Link Speeds are adjusted by custom code rather than in
a common function provided in PCI core. PCIe bandwidth controller
(bwctrl) introduces an in-kernel API to set PCIe Link Speed.

Convert Target Speed quirk to use the new API. The Target Speed quirk
runs very early when bwctrl is not yet probed for a Port and can also
run later when bwctrl is already setup for the Port, which requires the
per port mutex (set_speed_mutex) to be only taken if the bwctrl setup
is already complete.

The new API is also intended to be used in an upcoming commit that adds
a thermal cooling device to throttle PCIe bandwidth when thermal
thresholds are reached.

The PCIe bandwidth control procedure is as follows. The highest speed
supported by the Port and the PCIe device which is not higher than the
requested speed is selected and written into the Target Link Speed in
the Link Control 2 Register. Then bandwidth controller retrains the
PCIe Link.

Bandwidth Notifications enable the cur_bus_speed in the struct pci_bus
to keep track PCIe Link Speed changes. While Bandwidth Notifications
should also be generated when bandwidth controller alters the PCIe Link
Speed, a few platforms do not deliver LMBS interrupt after Link
Training as expected. Thus, after changing the Link Speed, bandwidth
controller makes additional read for the Link Status Register to ensure
cur_bus_speed is consistent with the new PCIe Link Speed.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/pci.h         |  20 +++++
 drivers/pci/pcie/bwctrl.c | 161 +++++++++++++++++++++++++++++++++++++-
 drivers/pci/quirks.c      |  17 +---
 include/linux/pci.h       |  10 +++
 4 files changed, 193 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 33ed324d1953..c8ea672c1892 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -331,6 +331,17 @@ void pci_disable_bridge_window(struct pci_dev *dev);
 struct pci_bus *pci_bus_get(struct pci_bus *bus);
 void pci_bus_put(struct pci_bus *bus);
 
+#define PCIE_LNKCAP_SLS2SPEED(lnkcap)					\
+({									\
+	((lnkcap) == PCI_EXP_LNKCAP_SLS_64_0GB ? PCIE_SPEED_64_0GT :	\
+	 (lnkcap) == PCI_EXP_LNKCAP_SLS_32_0GB ? PCIE_SPEED_32_0GT :	\
+	 (lnkcap) == PCI_EXP_LNKCAP_SLS_16_0GB ? PCIE_SPEED_16_0GT :	\
+	 (lnkcap) == PCI_EXP_LNKCAP_SLS_8_0GB ? PCIE_SPEED_8_0GT :	\
+	 (lnkcap) == PCI_EXP_LNKCAP_SLS_5_0GB ? PCIE_SPEED_5_0GT :	\
+	 (lnkcap) == PCI_EXP_LNKCAP_SLS_2_5GB ? PCIE_SPEED_2_5GT :	\
+	 PCI_SPEED_UNKNOWN);						\
+})
+
 /* PCIe link information from Link Capabilities 2 */
 #define PCIE_LNKCAP2_SLS2SPEED(lnkcap2) \
 	((lnkcap2) & PCI_EXP_LNKCAP2_SLS_64_0GB ? PCIE_SPEED_64_0GT : \
@@ -341,6 +352,15 @@ void pci_bus_put(struct pci_bus *bus);
 	 (lnkcap2) & PCI_EXP_LNKCAP2_SLS_2_5GB ? PCIE_SPEED_2_5GT : \
 	 PCI_SPEED_UNKNOWN)
 
+#define PCIE_LNKCTL2_TLS2SPEED(lnkctl2) \
+	((lnkctl2) == PCI_EXP_LNKCTL2_TLS_64_0GT ? PCIE_SPEED_64_0GT : \
+	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_32_0GT ? PCIE_SPEED_32_0GT : \
+	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_16_0GT ? PCIE_SPEED_16_0GT : \
+	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_8_0GT ? PCIE_SPEED_8_0GT : \
+	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_5_0GT ? PCIE_SPEED_5_0GT : \
+	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_2_5GT ? PCIE_SPEED_2_5GT : \
+	 PCI_SPEED_UNKNOWN)
+
 /* PCIe speed to Mb/s reduced by encoding overhead */
 #define PCIE_SPEED2MBS_ENC(speed) \
 	((speed) == PCIE_SPEED_64_0GT ? 64000*1/1 : \
diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 1b11b5da79d4..1d3680ea8e06 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -7,6 +7,11 @@
  * Copyright (C) 2019 Dell Inc
  * Copyright (C) 2023-2024 Intel Corporation
  *
+ * The PCIe bandwidth controller provides a way to alter PCIe Link Speeds
+ * and notify the operating system when the Link Width or Speed changes. The
+ * notification capability is required for all Root Ports and Downstream
+ * Ports supporting Link Width wider than x1 and/or multiple Link Speeds.
+ *
  * This service port driver hooks into the Bandwidth Notification interrupt
  * watching for changes or links becoming degraded in operation. It updates
  * the cached Current Link Speed that is exposed to user space through sysfs.
@@ -15,9 +20,12 @@
 #define dev_fmt(fmt) "bwctrl: " fmt
 
 #include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/bits.h>
 #include <linux/cleanup.h>
 #include <linux/errno.h>
 #include <linux/interrupt.h>
+#include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/rwsem.h>
 #include <linux/slab.h>
@@ -28,15 +36,160 @@
 
 /**
  * struct pcie_bwctrl_data - PCIe bandwidth controller
+ * @set_speed_mutex:	Serializes link speed changes
  * @lbms_count:		Count for LBMS (since last reset)
  */
 struct pcie_bwctrl_data {
+	struct mutex set_speed_mutex;
 	atomic_t lbms_count;
 };
 
 /* Prevents port removal during link speed changes and LBMS count accessors */
 static DECLARE_RWSEM(pcie_bwctrl_remove_rwsem);
 
+static bool pcie_valid_speed(enum pci_bus_speed speed)
+{
+	return (speed >= PCIE_SPEED_2_5GT) && (speed <= PCIE_SPEED_64_0GT);
+}
+
+static u16 pci_bus_speed2lnkctl2(enum pci_bus_speed speed)
+{
+	static const u8 speed_conv[] = {
+		[PCIE_SPEED_2_5GT] = PCI_EXP_LNKCTL2_TLS_2_5GT,
+		[PCIE_SPEED_5_0GT] = PCI_EXP_LNKCTL2_TLS_5_0GT,
+		[PCIE_SPEED_8_0GT] = PCI_EXP_LNKCTL2_TLS_8_0GT,
+		[PCIE_SPEED_16_0GT] = PCI_EXP_LNKCTL2_TLS_16_0GT,
+		[PCIE_SPEED_32_0GT] = PCI_EXP_LNKCTL2_TLS_32_0GT,
+		[PCIE_SPEED_64_0GT] = PCI_EXP_LNKCTL2_TLS_64_0GT,
+	};
+
+	if (WARN_ON_ONCE(!pcie_valid_speed(speed)))
+		return 0;
+
+	return speed_conv[speed];
+}
+
+static inline u16 pcie_supported_speeds2target_speed(u8 supported_speeds)
+{
+	return __fls(supported_speeds);
+}
+
+/**
+ * pcie_bwctrl_select_speed - Select Target Link Speed
+ * @port:	PCIe Port
+ * @speed_req:	requested PCIe Link Speed
+ *
+ * Select Target Link Speed by take into account Supported Link Speeds of
+ * both the Root Port and the Endpoint.
+ *
+ * Return: Target Link Speed (1=2.5GT/s, 2=5GT/s, 3=8GT/s, etc.)
+ */
+static u16 pcie_bwctrl_select_speed(struct pci_dev *port, enum pci_bus_speed speed_req)
+{
+	struct pci_bus *bus = port->subordinate;
+	u8 desired_speeds, supported_speeds;
+	struct pci_dev *dev;
+
+	desired_speeds = GENMASK(pci_bus_speed2lnkctl2(speed_req),
+				 __fls(PCI_EXP_LNKCAP2_SLS_2_5GB));
+
+	supported_speeds = port->supported_speeds;
+	if (bus) {
+		down_read(&pci_bus_sem);
+		dev = list_first_entry_or_null(&bus->devices, struct pci_dev, bus_list);
+		if (dev)
+			supported_speeds &= dev->supported_speeds;
+		up_read(&pci_bus_sem);
+	}
+	if (!supported_speeds)
+		return PCI_EXP_LNKCAP2_SLS_2_5GB;
+
+	return pcie_supported_speeds2target_speed(supported_speeds & desired_speeds);
+}
+
+static int pcie_bwctrl_change_speed(struct pci_dev *port, u16 target_speed, bool use_lt)
+{
+	int ret;
+
+	ret = pcie_capability_clear_and_set_word(port, PCI_EXP_LNKCTL2,
+						 PCI_EXP_LNKCTL2_TLS, target_speed);
+	if (ret != PCIBIOS_SUCCESSFUL)
+		return pcibios_err_to_errno(ret);
+
+	ret = pcie_retrain_link(port, use_lt);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Ensure link speed updates also with platforms that have problems
+	 * with notifications.
+	 */
+	if (port->subordinate)
+		pcie_update_link_speed(port->subordinate);
+
+	return 0;
+}
+
+/**
+ * pcie_set_target_speed - Set downstream Link Speed for PCIe Port
+ * @port:	PCIe Port
+ * @speed_req:	requested PCIe Link Speed
+ * @use_lt:	Wait for the LT or DLLLA bit to detect the end of link training
+ *
+ * Attempts to set PCIe Port Link Speed to @speed_req. @speed_req may be
+ * adjusted downwards to the best speed supported by both the Port and PCIe
+ * Device underneath it.
+ *
+ * Return:
+ * * 0		- on success
+ * * -EINVAL	- @speed_req is not a PCIe Link Speed
+ * * -ENODEV	- @port is not controllable
+ * * -ETIMEDOUT	- changing Link Speed took too long
+ * * -EAGAIN	- Link Speed was changed but @speed_req was not achieved
+ */
+int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
+			  bool use_lt)
+{
+	struct pci_bus *bus = port->subordinate;
+	u16 target_speed;
+	int ret;
+
+	if (WARN_ON_ONCE(!pcie_valid_speed(speed_req)))
+		return -EINVAL;
+
+	if (bus && bus->cur_bus_speed == speed_req)
+		return 0;
+
+	target_speed = pcie_bwctrl_select_speed(port, speed_req);
+
+	scoped_guard(rwsem_read, &pcie_bwctrl_remove_rwsem) {
+		struct pcie_bwctrl_data *data = port->link_bwctrl;
+
+		/*
+		 * port->link_bwctrl is NULL during initial scan when called
+		 * e.g. from the Target Speed quirk.
+		 */
+		if (data)
+			mutex_lock(&data->set_speed_mutex);
+
+		ret = pcie_bwctrl_change_speed(port, target_speed, use_lt);
+
+		if (data)
+			mutex_unlock(&data->set_speed_mutex);
+	}
+
+	/*
+	 * Despite setting higher speed into the Target Link Speed, empty
+	 * bus won't train to 5GT+ speeds.
+	 */
+	if (!ret && bus && bus->cur_bus_speed != speed_req &&
+	    !list_empty(&bus->devices))
+		ret = -EAGAIN;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pcie_set_target_speed);
+
 static void pcie_bwnotif_enable(struct pcie_device *srv)
 {
 	struct pcie_bwctrl_data *data = get_service_data(srv);
@@ -135,6 +288,7 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
 	if (!data)
 		return -ENOMEM;
 
+	mutex_init(&data->set_speed_mutex);
 	set_service_data(srv, data);
 
 	ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
@@ -142,8 +296,10 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
 	if (ret)
 		return ret;
 
-	port->link_bwctrl = no_free_ptr(data);
-	pcie_bwnotif_enable(srv);
+	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem) {
+		port->link_bwctrl = no_free_ptr(data);
+		pcie_bwnotif_enable(srv);
+	}
 
 	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
 
@@ -159,6 +315,7 @@ static void pcie_bwnotif_remove(struct pcie_device *srv)
 		srv->port->link_bwctrl = NULL;
 
 	free_irq(srv->irq, srv);
+	mutex_destroy(&data->set_speed_mutex);
 	kfree(data);
 }
 
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index e6d502dca939..dcf1c86a5488 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -113,16 +113,11 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 
 		pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
 
-		lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
-		lnkctl2 |= PCI_EXP_LNKCTL2_TLS_2_5GT;
-		pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
-
-		ret = pcie_retrain_link(dev, false);
+		ret = pcie_set_target_speed(dev, PCIE_SPEED_2_5GT, false);
 		if (ret) {
 			pci_info(dev, "retraining failed\n");
-			pcie_capability_write_word(dev, PCI_EXP_LNKCTL2,
-						   oldlnkctl2);
-			pcie_retrain_link(dev, true);
+			pcie_set_target_speed(dev, PCIE_LNKCTL2_TLS2SPEED(oldlnkctl2),
+					      true);
 			return ret;
 		}
 
@@ -136,11 +131,7 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 
 		pci_info(dev, "removing 2.5GT/s downstream link speed restriction\n");
 		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
-		lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
-		lnkctl2 |= lnkcap & PCI_EXP_LNKCAP_SLS;
-		pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
-
-		ret = pcie_retrain_link(dev, false);
+		ret = pcie_set_target_speed(dev, PCIE_LNKCAP_SLS2SPEED(lnkcap), false);
 		if (ret) {
 			pci_info(dev, "retraining failed\n");
 			return ret;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5f9de226be13..b5ce9513b06f 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1798,9 +1798,19 @@ static inline int pci_irqd_intx_xlate(struct irq_domain *d,
 #ifdef CONFIG_PCIEPORTBUS
 extern bool pcie_ports_disabled;
 extern bool pcie_ports_native;
+
+int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
+			  bool use_lt);
 #else
 #define pcie_ports_disabled	true
 #define pcie_ports_native	false
+
+static inline int pcie_set_target_speed(struct pci_dev *port,
+					enum pci_bus_speed speed_req,
+					bool use_lt)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 #define PCIE_LINK_STATE_L0S		(BIT(0) | BIT(1)) /* Upstr/dwnstr L0s */
-- 
2.39.5

Re: [PATCH v8 6/8] PCI/bwctrl: Add API to set PCIe Link Speed

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:21 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> Currently, PCIe Link Speeds are adjusted by custom code rather than in
> a common function provided in PCI core. PCIe bandwidth controller
> (bwctrl) introduces an in-kernel API to set PCIe Link Speed.
> 
> Convert Target Speed quirk to use the new API. The Target Speed quirk
> runs very early when bwctrl is not yet probed for a Port and can also
> run later when bwctrl is already setup for the Port, which requires the
> per port mutex (set_speed_mutex) to be only taken if the bwctrl setup
> is already complete.
> 
> The new API is also intended to be used in an upcoming commit that adds
> a thermal cooling device to throttle PCIe bandwidth when thermal
> thresholds are reached.
> 
> The PCIe bandwidth control procedure is as follows. The highest speed
> supported by the Port and the PCIe device which is not higher than the
> requested speed is selected and written into the Target Link Speed in
> the Link Control 2 Register. Then bandwidth controller retrains the
> PCIe Link.
> 
> Bandwidth Notifications enable the cur_bus_speed in the struct pci_bus
> to keep track PCIe Link Speed changes. While Bandwidth Notifications
> should also be generated when bandwidth controller alters the PCIe Link
> Speed, a few platforms do not deliver LMBS interrupt after Link
> Training as expected. Thus, after changing the Link Speed, bandwidth
> controller makes additional read for the Link Status Register to ensure
> cur_bus_speed is consistent with the new PCIe Link Speed.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Trivial stuff inline.  The mutex_destroy discussion is a just a consistency
thing given that call is rarely bothered with but here it might help with
debug.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Jonathan

> ---
>  drivers/pci/pci.h         |  20 +++++
>  drivers/pci/pcie/bwctrl.c | 161 +++++++++++++++++++++++++++++++++++++-
>  drivers/pci/quirks.c      |  17 +---
>  include/linux/pci.h       |  10 +++
>  4 files changed, 193 insertions(+), 15 deletions(-)
> 



> diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
> index 1b11b5da79d4..1d3680ea8e06 100644
> --- a/drivers/pci/pcie/bwctrl.c
> +++ b/drivers/pci/pcie/bwctrl.c
> @@ -7,6 +7,11 @@






>  static void pcie_bwnotif_enable(struct pcie_device *srv)
>  {
>  	struct pcie_bwctrl_data *data = get_service_data(srv);
> @@ -135,6 +288,7 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
>  	if (!data)
>  		return -ENOMEM;
>  
> +	mutex_init(&data->set_speed_mutex);
>  	set_service_data(srv, data);
>  
>  	ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
> @@ -142,8 +296,10 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
>  	if (ret)
>  		return ret;
>  
> -	port->link_bwctrl = no_free_ptr(data);
> -	pcie_bwnotif_enable(srv);
> +	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem) {

Calling it remove_rwsem and using it to protect against not yet
present seems odd. Maybe rename, pcie_bwctrl_bound_rswem or something like that?

> +		port->link_bwctrl = no_free_ptr(data);
> +		pcie_bwnotif_enable(srv);
> +	}
>  
>  	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
>  
> @@ -159,6 +315,7 @@ static void pcie_bwnotif_remove(struct pcie_device *srv)
>  		srv->port->link_bwctrl = NULL;
>  
>  	free_irq(srv->irq, srv);
> +	mutex_destroy(&data->set_speed_mutex);
Probably not worth doing.  Also you don't do error handling for this above.
Ideal is use devm_ for data and then devm_mutex_init()


>  	kfree(data);
>  }
>  

Re: [PATCH v8 6/8] PCI/bwctrl: Add API to set PCIe Link Speed

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 5455 bytes --]

On Thu, 17 Oct 2024, Jonathan Cameron wrote:

> On Wed,  9 Oct 2024 12:52:21 +0300
> Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> 
> > Currently, PCIe Link Speeds are adjusted by custom code rather than in
> > a common function provided in PCI core. PCIe bandwidth controller
> > (bwctrl) introduces an in-kernel API to set PCIe Link Speed.
> > 
> > Convert Target Speed quirk to use the new API. The Target Speed quirk
> > runs very early when bwctrl is not yet probed for a Port and can also
> > run later when bwctrl is already setup for the Port, which requires the
> > per port mutex (set_speed_mutex) to be only taken if the bwctrl setup
> > is already complete.
> > 
> > The new API is also intended to be used in an upcoming commit that adds
> > a thermal cooling device to throttle PCIe bandwidth when thermal
> > thresholds are reached.
> > 
> > The PCIe bandwidth control procedure is as follows. The highest speed
> > supported by the Port and the PCIe device which is not higher than the
> > requested speed is selected and written into the Target Link Speed in
> > the Link Control 2 Register. Then bandwidth controller retrains the
> > PCIe Link.
> > 
> > Bandwidth Notifications enable the cur_bus_speed in the struct pci_bus
> > to keep track PCIe Link Speed changes. While Bandwidth Notifications
> > should also be generated when bandwidth controller alters the PCIe Link
> > Speed, a few platforms do not deliver LMBS interrupt after Link
> > Training as expected. Thus, after changing the Link Speed, bandwidth
> > controller makes additional read for the Link Status Register to ensure
> > cur_bus_speed is consistent with the new PCIe Link Speed.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> 
> Trivial stuff inline.  The mutex_destroy discussion is a just a consistency
> thing given that call is rarely bothered with but here it might help with
> debug.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> Jonathan
> 
> > ---
> >  drivers/pci/pci.h         |  20 +++++
> >  drivers/pci/pcie/bwctrl.c | 161 +++++++++++++++++++++++++++++++++++++-
> >  drivers/pci/quirks.c      |  17 +---
> >  include/linux/pci.h       |  10 +++
> >  4 files changed, 193 insertions(+), 15 deletions(-)
> 
> 
> > diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
> > index 1b11b5da79d4..1d3680ea8e06 100644
> > --- a/drivers/pci/pcie/bwctrl.c
> > +++ b/drivers/pci/pcie/bwctrl.c
> > @@ -7,6 +7,11 @@
> 
> >  static void pcie_bwnotif_enable(struct pcie_device *srv)
> >  {
> >  	struct pcie_bwctrl_data *data = get_service_data(srv);
> > @@ -135,6 +288,7 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
> >  	if (!data)
> >  		return -ENOMEM;
> >  
> > +	mutex_init(&data->set_speed_mutex);
> >  	set_service_data(srv, data);
> >  
> >  	ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
> > @@ -142,8 +296,10 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
> >  	if (ret)
> >  		return ret;
> >  
> > -	port->link_bwctrl = no_free_ptr(data);
> > -	pcie_bwnotif_enable(srv);
> > +	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem) {
> 
> Calling it remove_rwsem and using it to protect against not yet
> present seems odd. Maybe rename, pcie_bwctrl_bound_rswem or something like that?

Okay but there's one related issue I need to address:

I came across recursive locking splat from pcie_bwctrl_remove_rwsem
(seems I had lockdep off for some odd reason in my config so it didn't
trigger during my testing until now). The splat is because of:

pcie_set_target_speed()
   scoped_guard(rwsem_read, &pcie_bwctrl_remove_rwsem)  
   -> pcie_bwctrl_change_speed
      -> pcie_retrain_link()
         -> pcie_reset_lbms_count()
            guard(rwsem_read)(&pcie_bwctrl_remove_rwsem);

I wouldn't want to special case pcie_retrain_link() just for BW 
control's sake, I plan to solve that by splitting pcie_bwctrl_remove_rwsem 
to have one for LBMS API and another for set speed API so split it into:

- pcie_bwctrl_setspeed_rwsem
- pcie_bwctrl_lbms_rwsem

It requires taking both in .probe and .remove which is not as elegant I'd 
want but definitely seems more elegant compared with differentiating 
pcie_retrain_link().

If you, for some reason would instead prefer I differentiated 
pcie_retrain_link() for cases when holding pcie_bwctrl_remove_rwsem 
already (or pcie_bwctrl_bound_rwsem as suggested by you), please let me 
know.

> > +		port->link_bwctrl = no_free_ptr(data);
> > +		pcie_bwnotif_enable(srv);
> > +	}
> >  
> >  	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
> >  
> > @@ -159,6 +315,7 @@ static void pcie_bwnotif_remove(struct pcie_device *srv)
> >  		srv->port->link_bwctrl = NULL;
> >  
> >  	free_irq(srv->irq, srv);
> > +	mutex_destroy(&data->set_speed_mutex);
>
> Probably not worth doing.  Also you don't do error handling for this above.

I'm not sure what error handling you're referring to?

> Ideal is use devm_ for data and then devm_mutex_init()

I've now converted alloc, irq, and mutex to devm. I had them at one point 
but then Lukas said it's the wrong direction consider what lies in future 
but since the future seeming has now changed I've no problem of making our
lives easier with devm. :-)

I also got rid of the service data use for your convinience.

-- 
 i.

[PATCH v8 7/8] thermal: Add PCIe cooling driver

[Ilpo Järvinen]

Add a thermal cooling driver to provide path to access PCIe bandwidth
controller using the usual thermal interfaces.

A cooling device is instantiated for controllable PCIe Ports from the
bwctrl service driver.

If registering the cooling device fails, allow bwctrl's probe to
succeed regardless. As cdev in that case contains IS_ERR() pseudo
"pointer", clean that up inside the probe function so the remove side
doesn't need to suddenly make an odd looking IS_ERR() check.

The thermal side state 0 means no throttling, i.e., maximum supported
PCIe Link Speed.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective
---
 MAINTAINERS                    |  2 +
 drivers/pci/pcie/bwctrl.c      | 11 +++++
 drivers/thermal/Kconfig        |  9 ++++
 drivers/thermal/Makefile       |  2 +
 drivers/thermal/pcie_cooling.c | 80 ++++++++++++++++++++++++++++++++++
 include/linux/pci-bwctrl.h     | 28 ++++++++++++
 6 files changed, 132 insertions(+)
 create mode 100644 drivers/thermal/pcie_cooling.c
 create mode 100644 include/linux/pci-bwctrl.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 8c555b3325d6..393ed7ce5ea1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17938,6 +17938,8 @@ M:	Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
 L:	linux-pci@vger.kernel.org
 S:	Supported
 F:	drivers/pci/pcie/bwctrl.c
+F:	drivers/thermal/pcie_cooling.c
+F:	include/linux/pci-bwctrl.h
 
 PCIE DRIVER FOR AMAZON ANNAPURNA LABS
 M:	Jonathan Chocron <jonnyc@amazon.com>
diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 1d3680ea8e06..0f686a2e636f 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -27,6 +27,7 @@
 #include <linux/interrupt.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
+#include <linux/pci-bwctrl.h>
 #include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -38,10 +39,12 @@
  * struct pcie_bwctrl_data - PCIe bandwidth controller
  * @set_speed_mutex:	Serializes link speed changes
  * @lbms_count:		Count for LBMS (since last reset)
+ * @cdev:		thermal cooling device associated with the port
  */
 struct pcie_bwctrl_data {
 	struct mutex set_speed_mutex;
 	atomic_t lbms_count;
+	struct thermal_cooling_device *cdev;
 };
 
 /* Prevents port removal during link speed changes and LBMS count accessors */
@@ -303,6 +306,11 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
 
 	pci_dbg(port, "enabled with IRQ %d\n", srv->irq);
 
+	/* Don't fail on errors. Don't leave IS_ERR() "pointer" into ->cdev */
+	port->link_bwctrl->cdev = pcie_cooling_device_register(port);
+	if (IS_ERR(port->link_bwctrl->cdev))
+		port->link_bwctrl->cdev = NULL;
+
 	return 0;
 }
 
@@ -310,6 +318,9 @@ static void pcie_bwnotif_remove(struct pcie_device *srv)
 {
 	struct pcie_bwctrl_data *data = get_service_data(srv);
 
+	if (data->cdev)
+		pcie_cooling_device_unregister(data->cdev);
+
 	pcie_bwnotif_disable(srv->port);
 	scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem)
 		srv->port->link_bwctrl = NULL;
diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 61e7ae524b1f..d3f9686e26e7 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
 
 	  If you want this support, you should say Y here.
 
+config PCIE_THERMAL
+	bool "PCIe cooling support"
+	depends on PCIEPORTBUS
+	help
+	  This implements PCIe cooling mechanism through bandwidth reduction
+	  for PCIe devices.
+
+	  If you want this support, you should say Y here.
+
 config THERMAL_EMULATION
 	bool "Thermal emulation mode support"
 	help
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 41c4d56beb40..210c16c91461 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -31,6 +31,8 @@ thermal_sys-$(CONFIG_CPU_IDLE_THERMAL)	+= cpuidle_cooling.o
 # devfreq cooling
 thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
 
+thermal_sys-$(CONFIG_PCIE_THERMAL) += pcie_cooling.o
+
 obj-$(CONFIG_K3_THERMAL)	+= k3_bandgap.o k3_j72xx_bandgap.o
 # platform thermal drivers
 obj-y				+= broadcom/
diff --git a/drivers/thermal/pcie_cooling.c b/drivers/thermal/pcie_cooling.c
new file mode 100644
index 000000000000..a876d64f1582
--- /dev/null
+++ b/drivers/thermal/pcie_cooling.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PCIe cooling device
+ *
+ * Copyright (C) 2023-2024 Intel Corporation
+ */
+
+#include <linux/build_bug.h>
+#include <linux/cleanup.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pci-bwctrl.h>
+#include <linux/slab.h>
+#include <linux/sprintf.h>
+#include <linux/thermal.h>
+
+#define COOLING_DEV_TYPE_PREFIX		"PCIe_Port_Link_Speed_"
+
+static int pcie_cooling_get_max_level(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+	struct pci_dev *port = cdev->devdata;
+
+	/* cooling state 0 is same as the maximum PCIe speed */
+	*state = port->subordinate->max_bus_speed - PCIE_SPEED_2_5GT;
+
+	return 0;
+}
+
+static int pcie_cooling_get_cur_level(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+	struct pci_dev *port = cdev->devdata;
+
+	/* cooling state 0 is same as the maximum PCIe speed */
+	*state = cdev->max_state - (port->subordinate->cur_bus_speed - PCIE_SPEED_2_5GT);
+
+	return 0;
+}
+
+static int pcie_cooling_set_cur_level(struct thermal_cooling_device *cdev, unsigned long state)
+{
+	struct pci_dev *port = cdev->devdata;
+	enum pci_bus_speed speed;
+
+	/* cooling state 0 is same as the maximum PCIe speed */
+	speed = (cdev->max_state - state) + PCIE_SPEED_2_5GT;
+
+	return pcie_set_target_speed(port, speed, true);
+}
+
+static struct thermal_cooling_device_ops pcie_cooling_ops = {
+	.get_max_state = pcie_cooling_get_max_level,
+	.get_cur_state = pcie_cooling_get_cur_level,
+	.set_cur_state = pcie_cooling_set_cur_level,
+};
+
+struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port)
+{
+	char *name __free(kfree) =
+		kasprintf(GFP_KERNEL, COOLING_DEV_TYPE_PREFIX "%s", pci_name(port));
+	if (!name)
+		return ERR_PTR(-ENOMEM);
+
+	return thermal_cooling_device_register(name, port, &pcie_cooling_ops);
+}
+
+void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev)
+{
+	thermal_cooling_device_unregister(cdev);
+}
+
+/* For bus_speed <-> state arithmetic */
+static_assert(PCIE_SPEED_2_5GT + 1 == PCIE_SPEED_5_0GT);
+static_assert(PCIE_SPEED_5_0GT + 1 == PCIE_SPEED_8_0GT);
+static_assert(PCIE_SPEED_8_0GT + 1 == PCIE_SPEED_16_0GT);
+static_assert(PCIE_SPEED_16_0GT + 1 == PCIE_SPEED_32_0GT);
+static_assert(PCIE_SPEED_32_0GT + 1 == PCIE_SPEED_64_0GT);
+
+MODULE_AUTHOR("Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>");
+MODULE_DESCRIPTION("PCIe cooling driver");
diff --git a/include/linux/pci-bwctrl.h b/include/linux/pci-bwctrl.h
new file mode 100644
index 000000000000..cee07127455b
--- /dev/null
+++ b/include/linux/pci-bwctrl.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * PCIe bandwidth controller
+ *
+ * Copyright (C) 2023-2024 Intel Corporation
+ */
+
+#ifndef LINUX_PCI_BWCTRL_H
+#define LINUX_PCI_BWCTRL_H
+
+#include <linux/pci.h>
+
+struct thermal_cooling_device;
+
+#ifdef CONFIG_PCIE_THERMAL
+struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port);
+void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev);
+#else
+static inline struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port)
+{
+	return NULL;
+}
+static inline void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev)
+{
+}
+#endif
+
+#endif
-- 
2.39.5

Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:22 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> Add a thermal cooling driver to provide path to access PCIe bandwidth
> controller using the usual thermal interfaces.
> 
> A cooling device is instantiated for controllable PCIe Ports from the
> bwctrl service driver.
> 
> If registering the cooling device fails, allow bwctrl's probe to
> succeed regardless. As cdev in that case contains IS_ERR() pseudo
> "pointer", clean that up inside the probe function so the remove side
> doesn't need to suddenly make an odd looking IS_ERR() check.
> 
> The thermal side state 0 means no throttling, i.e., maximum supported
> PCIe Link Speed.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective

Trivial thing noticed on a reread.


> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 61e7ae524b1f..d3f9686e26e7 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
>  
>  	  If you want this support, you should say Y here.
>  
> +config PCIE_THERMAL
> +	bool "PCIe cooling support"
> +	depends on PCIEPORTBUS
> +	help
> +	  This implements PCIe cooling mechanism through bandwidth reduction
> +	  for PCIe devices.

Technically links not devices, but don't think that matters much

Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1996 bytes --]

On Thu, 17 Oct 2024, Jonathan Cameron wrote:

> On Wed,  9 Oct 2024 12:52:22 +0300
> Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> 
> > Add a thermal cooling driver to provide path to access PCIe bandwidth
> > controller using the usual thermal interfaces.
> > 
> > A cooling device is instantiated for controllable PCIe Ports from the
> > bwctrl service driver.
> > 
> > If registering the cooling device fails, allow bwctrl's probe to
> > succeed regardless. As cdev in that case contains IS_ERR() pseudo
> > "pointer", clean that up inside the probe function so the remove side
> > doesn't need to suddenly make an odd looking IS_ERR() check.
> > 
> > The thermal side state 0 means no throttling, i.e., maximum supported
> > PCIe Link Speed.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective
> 
> Trivial thing noticed on a reread.
> 
> 
> > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > index 61e7ae524b1f..d3f9686e26e7 100644
> > --- a/drivers/thermal/Kconfig
> > +++ b/drivers/thermal/Kconfig
> > @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
> >  
> >  	  If you want this support, you should say Y here.
> >  
> > +config PCIE_THERMAL
> > +	bool "PCIe cooling support"
> > +	depends on PCIEPORTBUS
> > +	help
> > +	  This implements PCIe cooling mechanism through bandwidth reduction
> > +	  for PCIe devices.
> 
> Technically links not devices, but don't think that matters much

That distinction would be splitting hairs beyond what seems useful from 
ordinary user's point of view. If there's no device attached, BW 
controller cannot do anything since the link is not going to train.
The link speed reduction is going to impact the speed the device
can communicate with even if it technically occurs on the link.

-- 
 i.

Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

[Rafael J. Wysocki]

On Thu, Oct 17, 2024 at 2:16 PM Ilpo Järvinen
<ilpo.jarvinen@linux.intel.com> wrote:
>
> On Thu, 17 Oct 2024, Jonathan Cameron wrote:
>
> > On Wed,  9 Oct 2024 12:52:22 +0300
> > Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> >
> > > Add a thermal cooling driver to provide path to access PCIe bandwidth
> > > controller using the usual thermal interfaces.
> > >
> > > A cooling device is instantiated for controllable PCIe Ports from the
> > > bwctrl service driver.
> > >
> > > If registering the cooling device fails, allow bwctrl's probe to
> > > succeed regardless. As cdev in that case contains IS_ERR() pseudo
> > > "pointer", clean that up inside the probe function so the remove side
> > > doesn't need to suddenly make an odd looking IS_ERR() check.
> > >
> > > The thermal side state 0 means no throttling, i.e., maximum supported
> > > PCIe Link Speed.
> > >
> > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective
> >
> > Trivial thing noticed on a reread.
> >
> >
> > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > > index 61e7ae524b1f..d3f9686e26e7 100644
> > > --- a/drivers/thermal/Kconfig
> > > +++ b/drivers/thermal/Kconfig
> > > @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
> > >
> > >       If you want this support, you should say Y here.
> > >
> > > +config PCIE_THERMAL
> > > +   bool "PCIe cooling support"
> > > +   depends on PCIEPORTBUS
> > > +   help
> > > +     This implements PCIe cooling mechanism through bandwidth reduction
> > > +     for PCIe devices.
> >
> > Technically links not devices, but don't think that matters much
>
> That distinction would be splitting hairs beyond what seems useful from
> ordinary user's point of view. If there's no device attached, BW
> controller cannot do anything since the link is not going to train.
> The link speed reduction is going to impact the speed the device
> can communicate with even if it technically occurs on the link.

From the Kconfig description perspective I think it's better to say
"devices" even though technically it is about links, because device
performance is what users will measure and notice any changes of.

Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 2653 bytes --]

On Thu, 17 Oct 2024, Rafael J. Wysocki wrote:

> On Thu, Oct 17, 2024 at 2:16 PM Ilpo Järvinen
> <ilpo.jarvinen@linux.intel.com> wrote:
> >
> > On Thu, 17 Oct 2024, Jonathan Cameron wrote:
> >
> > > On Wed,  9 Oct 2024 12:52:22 +0300
> > > Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> > >
> > > > Add a thermal cooling driver to provide path to access PCIe bandwidth
> > > > controller using the usual thermal interfaces.
> > > >
> > > > A cooling device is instantiated for controllable PCIe Ports from the
> > > > bwctrl service driver.
> > > >
> > > > If registering the cooling device fails, allow bwctrl's probe to
> > > > succeed regardless. As cdev in that case contains IS_ERR() pseudo
> > > > "pointer", clean that up inside the probe function so the remove side
> > > > doesn't need to suddenly make an odd looking IS_ERR() check.
> > > >
> > > > The thermal side state 0 means no throttling, i.e., maximum supported
> > > > PCIe Link Speed.
> > > >
> > > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective
> > >
> > > Trivial thing noticed on a reread.
> > >
> > >
> > > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > > > index 61e7ae524b1f..d3f9686e26e7 100644
> > > > --- a/drivers/thermal/Kconfig
> > > > +++ b/drivers/thermal/Kconfig
> > > > @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
> > > >
> > > >       If you want this support, you should say Y here.
> > > >
> > > > +config PCIE_THERMAL
> > > > +   bool "PCIe cooling support"
> > > > +   depends on PCIEPORTBUS
> > > > +   help
> > > > +     This implements PCIe cooling mechanism through bandwidth reduction
> > > > +     for PCIe devices.
> > >
> > > Technically links not devices, but don't think that matters much
> >
> > That distinction would be splitting hairs beyond what seems useful from
> > ordinary user's point of view. If there's no device attached, BW
> > controller cannot do anything since the link is not going to train.
> > The link speed reduction is going to impact the speed the device
> > can communicate with even if it technically occurs on the link.
> 
> From the Kconfig description perspective I think it's better to say
> "devices" even though technically it is about links, because device
> performance is what users will measure and notice any changes of.

Yes, that's what I tried to explain above. I intend to keep it as 
"devices" for this very reason.

-- 
 i.

Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

[Jonathan Cameron]

On Thu, 17 Oct 2024 16:02:34 +0300 (EEST)
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> On Thu, 17 Oct 2024, Rafael J. Wysocki wrote:
> 
> > On Thu, Oct 17, 2024 at 2:16 PM Ilpo Järvinen
> > <ilpo.jarvinen@linux.intel.com> wrote:  
> > >
> > > On Thu, 17 Oct 2024, Jonathan Cameron wrote:
> > >  
> > > > On Wed,  9 Oct 2024 12:52:22 +0300
> > > > Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> > > >  
> > > > > Add a thermal cooling driver to provide path to access PCIe bandwidth
> > > > > controller using the usual thermal interfaces.
> > > > >
> > > > > A cooling device is instantiated for controllable PCIe Ports from the
> > > > > bwctrl service driver.
> > > > >
> > > > > If registering the cooling device fails, allow bwctrl's probe to
> > > > > succeed regardless. As cdev in that case contains IS_ERR() pseudo
> > > > > "pointer", clean that up inside the probe function so the remove side
> > > > > doesn't need to suddenly make an odd looking IS_ERR() check.
> > > > >
> > > > > The thermal side state 0 means no throttling, i.e., maximum supported
> > > > > PCIe Link Speed.
> > > > >
> > > > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > > > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > > Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective  
> > > >
> > > > Trivial thing noticed on a reread.
> > > >
> > > >  
> > > > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > > > > index 61e7ae524b1f..d3f9686e26e7 100644
> > > > > --- a/drivers/thermal/Kconfig
> > > > > +++ b/drivers/thermal/Kconfig
> > > > > @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
> > > > >
> > > > >       If you want this support, you should say Y here.
> > > > >
> > > > > +config PCIE_THERMAL
> > > > > +   bool "PCIe cooling support"
> > > > > +   depends on PCIEPORTBUS
> > > > > +   help
> > > > > +     This implements PCIe cooling mechanism through bandwidth reduction
> > > > > +     for PCIe devices.  
> > > >
> > > > Technically links not devices, but don't think that matters much  
> > >
> > > That distinction would be splitting hairs beyond what seems useful from
> > > ordinary user's point of view. If there's no device attached, BW
> > > controller cannot do anything since the link is not going to train.
> > > The link speed reduction is going to impact the speed the device
> > > can communicate with even if it technically occurs on the link.  
> > 
> > From the Kconfig description perspective I think it's better to say
> > "devices" even though technically it is about links, because device
> > performance is what users will measure and notice any changes of.  
> 
> Yes, that's what I tried to explain above. I intend to keep it as 
> "devices" for this very reason.
> 
Fine by me to keep it as things stand. Been reading too many specs
recently so my immediate thought was why is there a bandwidth control
for the engines / memory in the EP :)

Jonathan

[PATCH v8 8/8] selftests/pcie_bwctrl: Create selftests

[Ilpo Järvinen]

Create selftests for PCIe BW control through the PCIe cooling device
sysfs interface.

First, the BW control selftest finds the PCIe Port to test with. By
default, the PCIe Port with the highest Link Speed is selected but
another PCIe Port can be provided with -d parameter.

The actual test steps the cur_state of the cooling device one-by-one
from max_state to what the cur_state was initially. The speed change
is confirmed by observing the current_link_speed for the corresponding
PCIe Port.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 MAINTAINERS                                   |   1 +
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/pcie_bwctrl/Makefile  |   2 +
 .../pcie_bwctrl/set_pcie_cooling_state.sh     | 122 ++++++++++++++++++
 .../selftests/pcie_bwctrl/set_pcie_speed.sh   |  67 ++++++++++
 5 files changed, 193 insertions(+)
 create mode 100644 tools/testing/selftests/pcie_bwctrl/Makefile
 create mode 100755 tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh
 create mode 100755 tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh

diff --git a/MAINTAINERS b/MAINTAINERS
index 393ed7ce5ea1..d7ffef4382df 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17940,6 +17940,7 @@ S:	Supported
 F:	drivers/pci/pcie/bwctrl.c
 F:	drivers/thermal/pcie_cooling.c
 F:	include/linux/pci-bwctrl.h
+F:	tools/testing/selftests/pcie_bwctrl/
 
 PCIE DRIVER FOR AMAZON ANNAPURNA LABS
 M:	Jonathan Chocron <jonnyc@amazon.com>
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index b38199965f99..7181756f47ff 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -72,6 +72,7 @@ TARGETS += net/packetdrill
 TARGETS += net/rds
 TARGETS += net/tcp_ao
 TARGETS += nsfs
+TARGETS += pcie_bwctrl
 TARGETS += perf_events
 TARGETS += pidfd
 TARGETS += pid_namespace
diff --git a/tools/testing/selftests/pcie_bwctrl/Makefile b/tools/testing/selftests/pcie_bwctrl/Makefile
new file mode 100644
index 000000000000..3e84e26341d1
--- /dev/null
+++ b/tools/testing/selftests/pcie_bwctrl/Makefile
@@ -0,0 +1,2 @@
+TEST_PROGS = set_pcie_cooling_state.sh
+include ../lib.mk
diff --git a/tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh b/tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh
new file mode 100755
index 000000000000..9df606552af3
--- /dev/null
+++ b/tools/testing/selftests/pcie_bwctrl/set_pcie_cooling_state.sh
@@ -0,0 +1,122 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+SYSFS=
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+retval=0
+skipmsg="skip all tests:"
+
+PCIEPORTTYPE="PCIe_Port_Link_Speed"
+
+prerequisite()
+{
+	local ports
+
+	if [ $UID != 0 ]; then
+		echo $skipmsg must be run as root >&2
+		exit $ksft_skip
+	fi
+
+	SYSFS=`mount -t sysfs | head -1 | awk '{ print $3 }'`
+
+	if [ ! -d "$SYSFS" ]; then
+		echo $skipmsg sysfs is not mounted >&2
+		exit $ksft_skip
+	fi
+
+	if ! ls $SYSFS/class/thermal/cooling_device* > /dev/null 2>&1; then
+		echo $skipmsg thermal cooling devices missing >&2
+		exit $ksft_skip
+	fi
+
+	ports=`grep -e "^$PCIEPORTTYPE" $SYSFS/class/thermal/cooling_device*/type | wc -l`
+	if [ $ports -eq 0 ]; then
+		echo $skipmsg pcie cooling devices missing >&2
+		exit $ksft_skip
+	fi
+}
+
+testport=
+find_pcie_port()
+{
+	local patt="$1"
+	local pcieports
+	local max
+	local cur
+	local delta
+	local bestdelta=-1
+
+	pcieports=`grep -l -F -e "$patt" /sys/class/thermal/cooling_device*/type`
+	if [ -z "$pcieports" ]; then
+		return
+	fi
+	pcieports=${pcieports//\/type/}
+	# Find the port with the highest PCIe Link Speed
+	for port in $pcieports; do
+		max=`cat $port/max_state`
+		cur=`cat $port/cur_state`
+		delta=$((max-cur))
+		if [ $delta -gt $bestdelta ]; then
+			testport="$port"
+			bestdelta=$delta
+		fi
+	done
+}
+
+sysfspcidev=
+find_sysfs_pci_dev()
+{
+	local typefile="$1/type"
+	local pcidir
+
+	pcidir="$SYSFS/bus/pci/devices/`sed -e "s|^${PCIEPORTTYPE}_||g" $typefile`"
+
+	if [ -r "$pcidir/current_link_speed" ]; then
+		sysfspcidev="$pcidir/current_link_speed"
+	fi
+}
+
+usage()
+{
+	echo "Usage $0 [ -d dev ]"
+	echo -e "\t-d: PCIe port BDF string (e.g., 0000:00:04.0)"
+}
+
+pattern="$PCIEPORTTYPE"
+parse_arguments()
+{
+	while getopts d:h opt; do
+		case $opt in
+			h)
+				usage "$0"
+				exit 0
+				;;
+			d)
+				pattern="$PCIEPORTTYPE_$OPTARG"
+				;;
+			*)
+				usage "$0"
+				exit 0
+				;;
+		esac
+	done
+}
+
+parse_arguments "$@"
+prerequisite
+find_pcie_port "$pattern"
+if [ -z "$testport" ]; then
+	echo $skipmsg "pcie cooling device not found from sysfs" >&2
+	exit $ksft_skip
+fi
+find_sysfs_pci_dev "$testport"
+if [ -z "$sysfspcidev" ]; then
+	echo $skipmsg "PCIe port device not found from sysfs" >&2
+	exit $ksft_skip
+fi
+
+./set_pcie_speed.sh "$testport" "$sysfspcidev"
+retval=$?
+
+exit $retval
diff --git a/tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh b/tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh
new file mode 100755
index 000000000000..584596949312
--- /dev/null
+++ b/tools/testing/selftests/pcie_bwctrl/set_pcie_speed.sh
@@ -0,0 +1,67 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set -e
+
+TESTNAME=set_pcie_speed
+
+declare -a PCIELINKSPEED=(
+	"2.5 GT/s PCIe"
+	"5.0 GT/s PCIe"
+	"8.0 GT/s PCIe"
+	"16.0 GT/s PCIe"
+	"32.0 GT/s PCIe"
+	"64.0 GT/s PCIe"
+)
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+retval=0
+
+coolingdev="$1"
+statefile="$coolingdev/cur_state"
+maxfile="$coolingdev/max_state"
+linkspeedfile="$2"
+
+oldstate=`cat $statefile`
+maxstate=`cat $maxfile`
+
+set_state()
+{
+	local state=$1
+	local linkspeed
+	local expected_linkspeed
+
+	echo $state > $statefile
+
+	sleep 1
+
+	linkspeed="`cat $linkspeedfile`"
+	expected_linkspeed=$((maxstate-state))
+	expected_str="${PCIELINKSPEED[$expected_linkspeed]}"
+	if [ ! "${expected_str}" = "${linkspeed}" ]; then
+		echo "$TESTNAME failed: expected: ${expected_str}; got ${linkspeed}"
+		retval=1
+	fi
+}
+
+cleanup_skip ()
+{
+	set_state $oldstate
+	exit $ksft_skip
+}
+
+trap cleanup_skip EXIT
+
+echo "$TESTNAME: testing states $maxstate .. $oldstate with $coolingdev"
+for i in $(seq $maxstate -1 $oldstate); do
+	set_state "$i"
+done
+
+trap EXIT
+if [ $retval -eq 0 ]; then
+	echo "$TESTNAME [PASS]"
+else
+	echo "$TESTNAME [FAIL]"
+fi
+exit $retval
-- 
2.39.5

Re: [PATCH v8 8/8] selftests/pcie_bwctrl: Create selftests

[Jonathan Cameron]

On Wed,  9 Oct 2024 12:52:23 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> Create selftests for PCIe BW control through the PCIe cooling device
> sysfs interface.
> 
> First, the BW control selftest finds the PCIe Port to test with. By
> default, the PCIe Port with the highest Link Speed is selected but
> another PCIe Port can be provided with -d parameter.
> 
> The actual test steps the cur_state of the cooling device one-by-one
> from max_state to what the cur_state was initially. The speed change
> is confirmed by observing the current_link_speed for the corresponding
> PCIe Port.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

My bash is terrible, but as far as I can tell this looks reasonable.
So with that in mind take this with a pinch of salt.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>