[PATCH v7 0/8] PCI: Add PCIe bandwidth controller

[PATCH v7 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.

V7 does substantial change into the interactions with the Target Speed
quirk which in v6 were not taking into account how early the quirk
runs. While I believe the challenges are mostly addressed now, it would
certainly be useful to have a second opinion on the chosen solutions.
These challenges will also be covered as a part of my upcoming talk at
VFIO/IOMMU/PCI microconference in Vienna.

bwctrl is built on top of BW notifications revert. The changes are
based on top of the Target Speed quirk fixes in pci/enumeration branch.

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                             |  42 +-
 drivers/pci/pcie/Kconfig                      |  12 +
 drivers/pci/pcie/Makefile                     |   1 +
 drivers/pci/pcie/bwctrl.c                     | 397 ++++++++++++++++++
 drivers/pci/pcie/portdrv.c                    |   9 +-
 drivers/pci/pcie/portdrv.h                    |  10 +-
 drivers/pci/probe.c                           |  15 +-
 drivers/pci/quirks.c                          |  32 +-
 drivers/thermal/Kconfig                       |  10 +
 drivers/thermal/Makefile                      |   2 +
 drivers/thermal/pcie_cooling.c                |  80 ++++
 include/linux/pci-bwctrl.h                    |  28 ++
 include/linux/pci.h                           |  19 +-
 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 +++
 23 files changed, 887 insertions(+), 53 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

-- 
2.39.2

[PATCH v7 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 4cf89a4b4cbc..25362d577824 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1270,6 +1270,7 @@ 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);
-- 
2.39.2

[PATCH v7 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 d46652760b11..699531d9d112 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6169,38 +6169,60 @@ 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 b14b9876c030..761b0538afe6 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1945,6 +1945,9 @@ 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 25362d577824..56ad75c4c994 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 */
@@ -518,6 +526,7 @@ struct pci_dev {
 	struct xarray	doe_mbs;	/* Data Object Exchange mailboxes */
 #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 94c00996e633..b8140fc184cc 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -676,6 +676,7 @@
 #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 */
-- 
2.39.2

[PATCH v7 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 061f01f60db4..b83ed2727c2f 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 7c06e55c5072..d723cf48c67a 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -360,7 +360,12 @@ 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 761b0538afe6..1b3747069464 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);
 	}
 }
 
-- 
2.39.2

[PATCH v7 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 5d57ea27dbc4..6fd9e8401c74 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");
-- 
2.39.2

[PATCH v7 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                 |  15 +++
 drivers/pci/pcie/Kconfig          |  12 ++
 drivers/pci/pcie/Makefile         |   1 +
 drivers/pci/pcie/bwctrl.c         | 190 ++++++++++++++++++++++++++++++
 drivers/pci/pcie/portdrv.c        |   9 +-
 drivers/pci/pcie/portdrv.h        |  10 +-
 drivers/pci/quirks.c              |   9 +-
 include/linux/pci.h               |   4 +
 11 files changed, 255 insertions(+), 8 deletions(-)
 create mode 100644 drivers/pci/pcie/bwctrl.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 42decde38320..d2e418350883 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17669,6 +17669,12 @@ 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 699531d9d112..a10ca0e80ce9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4724,7 +4724,7 @@ 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 d723cf48c67a..869677ff752f 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -671,6 +671,21 @@ static inline void pcie_set_ecrc_checking(struct pci_dev *dev) { }
 static inline void pcie_ecrc_get_policy(char *str) { }
 #endif
 
+#ifdef CONFIG_PCIE_BWCTRL
+void pcie_reset_lbms_count(struct pci_dev *port);
+int pcie_lbms_count(struct pci_dev *port, unsigned long *val);
+#elif defined(CONFIG_PCI)
+static inline void pcie_reset_lbms_count(struct pci_dev *port)
+{
+	pcie_capability_write_word(port, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS);
+}
+
+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/Kconfig b/drivers/pci/pcie/Kconfig
index 17919b99fa66..a8c27e37b3c7 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -146,6 +146,18 @@ config PCIE_PTM
 	  This is only useful if you have devices that support PTM, but it
 	  is safe to enable even if you don't.
 
+config PCIE_BWCTRL
+	bool "PCI Express Bandwidth Controller"
+	depends on PCIEPORTBUS
+	help
+	  This enables PCI Express Bandwidth Controller. The Bandwidth
+	  Controller allows controlling PCIe Link Speed and listens for Link
+	  Bandwidth Change Notifications. The current Link Speed is available
+	  through /sys/bus/pci/devices/.../current_link_speed.
+
+	  If you know Link Width or Speed changes occur (e.g., to correct
+	  unreliable links), you may answer Y.
+
 config PCIE_EDR
 	bool "PCI Express Error Disconnect Recover support"
 	depends on PCIE_DPC && ACPI
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 6461aa93fe76..6357bc219632 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -12,4 +12,5 @@ obj-$(CONFIG_PCIEAER_INJECT)	+= aer_inject.o
 obj-$(CONFIG_PCIE_PME)		+= pme.o
 obj-$(CONFIG_PCIE_DPC)		+= dpc.o
 obj-$(CONFIG_PCIE_PTM)		+= ptm.o
+obj-$(CONFIG_PCIE_BWCTRL)	+= bwctrl.o
 obj-$(CONFIG_PCIE_EDR)		+= edr.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..13366175da22 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 +51,12 @@ int pcie_dpc_init(void);
 static inline int pcie_dpc_init(void) { return 0; }
 #endif
 
+#ifdef CONFIG_PCIE_BWCTRL
+int pcie_bwctrl_init(void);
+#else
+static inline int pcie_bwctrl_init(void) { return 0; }
+#endif
+
 /* Port Type */
 #define PCIE_ANY_PORT			(~0)
 
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 6fd9e8401c74..64d9f8559f65 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 56ad75c4c994..d77816f0193f 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;
@@ -502,6 +503,9 @@ struct pci_dev {
 	unsigned int	dpc_rp_extensions:1;
 	u8		dpc_rp_log_size;
 #endif
+#ifdef CONFIG_PCIE_BWCTRL
+	struct pcie_bwctrl_data		*link_bwctrl;
+#endif
 #ifdef CONFIG_PCI_ATS
 	union {
 		struct pci_sriov	*sriov;		/* PF: SR-IOV info */
-- 
2.39.2

[PATCH v7 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. Also, the new API
has to be available for the Target Speed quirk when bwctrl is not
enabled by the config. The cases when bwctrl is not setup for the port
use less locking which is handled by a few locking wrappers.

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/Makefile |   2 +-
 drivers/pci/pcie/bwctrl.c | 200 +++++++++++++++++++++++++++++++++++++-
 drivers/pci/quirks.c      |  17 +---
 include/linux/pci.h       |   3 +
 5 files changed, 226 insertions(+), 16 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 869677ff752f..7f0e71f3ce67 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -313,6 +313,17 @@ 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 : \
@@ -323,6 +334,15 @@ 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/Makefile b/drivers/pci/pcie/Makefile
index 6357bc219632..e8cf58a0fa3f 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -12,5 +12,5 @@ obj-$(CONFIG_PCIEAER_INJECT)	+= aer_inject.o
 obj-$(CONFIG_PCIE_PME)		+= pme.o
 obj-$(CONFIG_PCIE_DPC)		+= dpc.o
 obj-$(CONFIG_PCIE_PTM)		+= ptm.o
-obj-$(CONFIG_PCIE_BWCTRL)	+= bwctrl.o
+obj-y				+= bwctrl.o
 obj-$(CONFIG_PCIE_EDR)		+= edr.o
diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 1b11b5da79d4..cc245aaf8d5e 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 +36,198 @@
 
 /**
  * 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;
 };
 
+#ifdef CONFIG_PCIE_BWCTRL
 /* Prevents port removal during link speed changes and LBMS count accessors */
 static DECLARE_RWSEM(pcie_bwctrl_remove_rwsem);
 
+static inline void pcie_bwctrl_remove_rwsem_down_read(void)
+{
+	down_read(&pcie_bwctrl_remove_rwsem);
+}
+
+static inline void pcie_bwctrl_remove_rwsem_up_read(void)
+{
+	up_read(&pcie_bwctrl_remove_rwsem);
+}
+
+static inline void pcie_bwctrl_port_mutex_lock(struct pci_dev *port)
+{
+	struct pcie_bwctrl_data *data;
+
+	/*
+	 * port->link_bwctrl is NULL when Target Speed quirk runs during
+	 * boot and when bwctrl is not enabled by the config.
+	 */
+	data = port->link_bwctrl;
+	if (!data)
+		return;
+
+	mutex_lock(&data->set_speed_mutex);
+}
+
+static inline void pcie_bwctrl_port_mutex_unlock(struct pci_dev *port)
+{
+	struct pcie_bwctrl_data *data;
+
+	/*
+	 * port->link_bwctrl is NULL when Target Speed quirk runs during
+	 * boot and when bwctrl is not enabled by the config.
+	 */
+	data = port->link_bwctrl;
+	if (!data)
+		return;
+
+	mutex_unlock(&data->set_speed_mutex);
+}
+#else
+static inline void pcie_bwctrl_remove_rwsem_down_read(void) {}
+static inline void pcie_bwctrl_remove_rwsem_up_read(void) {}
+static inline void pcie_bwctrl_port_mutex_lock(struct pci_dev *port) {}
+static inline void pcie_bwctrl_port_mutex_unlock(struct pci_dev *port) {}
+#endif /* CONFIG_PCIE_BWCTRL */
+
+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);
+
+	pcie_bwctrl_remove_rwsem_down_read();
+	pcie_bwctrl_port_mutex_lock(port);
+	ret = pcie_bwctrl_change_speed(port, target_speed, use_lt);
+	pcie_bwctrl_port_mutex_unlock(port);
+	pcie_bwctrl_remove_rwsem_up_read();
+
+	/*
+	 * 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);
+
+#ifdef CONFIG_PCIE_BWCTRL
 static void pcie_bwnotif_enable(struct pcie_device *srv)
 {
 	struct pcie_bwctrl_data *data = get_service_data(srv);
@@ -135,6 +326,7 @@ 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 +334,10 @@ 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 +353,7 @@ 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);
 }
 
@@ -188,3 +383,4 @@ int __init pcie_bwctrl_init(void)
 {
 	return pcie_port_service_register(&pcie_bwctrl_driver);
 }
+#endif	/* CONFIG_PCIE_BWCTRL */
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 64d9f8559f65..3bca70da1d45 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 d77816f0193f..3af842e6346d 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1845,6 +1845,9 @@ bool pci_aer_available(void);
 static inline bool pci_aer_available(void) { return false; }
 #endif
 
+int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
+			  bool use_lt);
+
 bool pci_ats_disabled(void);
 
 #ifdef CONFIG_PCIE_PTM
-- 
2.39.2

[PATCH v7 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        | 10 +++++
 drivers/thermal/Makefile       |  2 +
 drivers/thermal/pcie_cooling.c | 80 ++++++++++++++++++++++++++++++++++
 include/linux/pci-bwctrl.h     | 28 ++++++++++++
 6 files changed, 133 insertions(+)
 create mode 100644 drivers/thermal/pcie_cooling.c
 create mode 100644 include/linux/pci-bwctrl.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d2e418350883..47542dcb9259 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17674,6 +17674,8 @@ 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 cc245aaf8d5e..592a14183df8 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;
 };
 
 #ifdef CONFIG_PCIE_BWCTRL
@@ -341,6 +344,11 @@ 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;
 }
 
@@ -348,6 +356,9 @@ 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 ed16897584b4..648e0478d9d6 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -211,6 +211,16 @@ config DEVFREQ_THERMAL
 
 	  If you want this support, you should say Y here.
 
+config PCIE_THERMAL
+	bool "PCIe cooling support"
+	depends on PCIEPORTBUS
+	select PCIE_BWCTRL
+	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 ce7a4752ef52..33cb16b06ba5 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
-- 
2.39.2

[PATCH v7 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 47542dcb9259..dc601dcab8c6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17676,6 +17676,7 @@ 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 bc8fe9e8f7f2..086af950930c 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -69,6 +69,7 @@ TARGETS += net/openvswitch
 TARGETS += net/tcp_ao
 TARGETS += net/netfilter
 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
-- 
2.39.2