[PATCH v3 00/11] bus: mhi: host: Add support for mhi bus bw

[PATCH v3 00/11] bus: mhi: host: Add support for mhi bus bw

[Krishna Chaitanya Chundru]

As per MHI spec sec 14, MHI supports bandwidth scaling to reduce power
consumption. MHI bandwidth scaling is advertised in devices that contain
the bandwidth scaling capability registers. If enabled, the device
aggregates bandwidth requirements and sends them to the host in the form
of an event. After the host performs the bandwidth switch, it sends an
acknowledgment by ringing a doorbell.

if the host supports bandwidth scaling events, then it must set
BW_CFG.ENABLED bit, set BW_CFG.DB_CHAN_ID to the channel ID to the
doorbell that will be used by the host to communicate the bandwidth
scaling status and BW_CFG.ER_INDEX to the index for the event ring
to which the device should send bandwidth scaling request in the
bandwidth scaling capability register.

As part of mmio init check if the bw scale capability is present or not,
if present advertise host supports bw scale by setting all the required
fields.

MHI layer will only forward the bw scaling request to the controller
driver, it is responsibility of the controller driver to do actual bw
scaling and then pass status to the MHI. MHI will response back to the
device based up on the status of the bw scale received.

Add a new get_misc_doorbell() to get doorbell for misc capabilities to
use the doorbell with mhi events like MHI BW scale etc.

Use workqueue & mutex for the bw scale events as the pci_set_target_speed()
which will called by the mhi controller driver can sleep.

If the driver want to move higher data rate/speed then the current data
rate/speed then the controller driver may need to change certain votes
so that link may come up in requested data rate/speed like QCOM PCIe
controllers need to change their RPMh (Resource Power Manager-hardened)
state. And also once link retraining is done controller drivers needs
to adjust their votes based on the final data rate/speed.

Some controllers also may need to update their bandwidth voting like
ICC bw votings etc.

So, add pre_scale_bus_bw() & post_scale_bus_bw() op to call before & after
the link re-train. There is no explicit locking mechanisms as these are
called by a single client endpoint driver

In case of PCIe switch, if there is a request to change target speed for a
downstream port then no need to call these function ops as these are
outside the scope of the controller drivers.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
Changes in v3:
- Move update speed logic to pwrctrl driver (Mani)
- Move pre_bus_bw & post_bus_bw to bridge as these are bridge driver specific ops,
it feels to me we need to add these in the host bridge driver similar to recently
added one reset_slot.
- Remove dwc level wrapper (Mani)
- Enable ASPM only if they are enabled already (Mani)
- Change the name of mhi_get_capability_offset to mhi_find_capability() (Bjorn)
- Fix comments in the code, subjects etc (Mani & Bjorn)
- Link to v2: https://lore.kernel.org/r/20250313-mhi_bw_up-v2-0-869ca32170bf@oss.qualcomm.com

Changes in v2:
- Update the comments.
- Split the icc bw patch as sepertate one (Bjorn)
- update the aspm disablement comment (Bjorn)
- Use FIELD_GET & FIELD_PREP instead of hard macros and couple of nits
  suggested by (Ilpo Järvinen)
- Create a new function to change lnkcntrl2speed to enum pci_bus_speed (Jeff)
- Link to v1: https://lore.kernel.org/r/20250217-mhi_bw_up-v1-0-9bad1e42bdb1@oss.qualcomm.com

---
Krishna Chaitanya Chundru (9):
      PCI: Update current bus speed as part of pci_pwrctrl_notify()
      PCI/bwctrl: Add support to scale bandwidth before & after link re-training
      PCI/ASPM: Return enabled ASPM states as part of pcie_aspm_enabled()
      PCI/ASPM: Clear aspm_disable as part of __pci_enable_link_state()
      PCI: qcom: Extract core logic from qcom_pcie_icc_opp_update()
      PCI: qcom: Add support for PCIe bus bw scaling
      bus: mhi: host: Add support for Bandwidth scale
      PCI: Export pci_set_target_speed()
      PCI: Add function to convert lnkctl2speed to pci_bus_speed

Miaoqing Pan (1):
      wifi: ath11k: Add support for MHI bandwidth scaling

Vivek Pernamitta (1):
      bus: mhi: host: Add support to read MHI capabilities

 drivers/bus/mhi/common.h               |  20 ++++++
 drivers/bus/mhi/host/init.c            |  90 +++++++++++++++++++++++-
 drivers/bus/mhi/host/internal.h        |   7 +-
 drivers/bus/mhi/host/main.c            |  98 +++++++++++++++++++++++++-
 drivers/bus/mhi/host/pm.c              |  10 ++-
 drivers/net/wireless/ath/ath11k/mhi.c  |  41 +++++++++++
 drivers/pci/controller/dwc/pcie-qcom.c | 124 ++++++++++++++++++++++++++-------
 drivers/pci/pci.c                      |  12 ++++
 drivers/pci/pcie/aspm.c                |   5 +-
 drivers/pci/pcie/bwctrl.c              |  16 +++++
 drivers/pci/pwrctrl/core.c             |   5 ++
 include/linux/mhi.h                    |  13 ++++
 include/linux/pci.h                    |  19 ++++-
 13 files changed, 425 insertions(+), 35 deletions(-)
---
base-commit: fee3e843b309444f48157e2188efa6818bae85cf
change-id: 20250217-mhi_bw_up-f31306a5631b

Best regards,
-- 
Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>

[PATCH v3 01/11] PCI: Update current bus speed as part of pci_pwrctrl_notify()

[Krishna Chaitanya Chundru]

If the link is not up till the pwrctl drivers enable power to endpoints
then cur_bus_speed will not be updated with correct speed.

As part of rescan, pci_pwrctrl_notify() will be called when new devices
are added and as part of it update the link bus speed.

Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pwrctrl/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/pci/pwrctrl/core.c b/drivers/pci/pwrctrl/core.c
index 9cc7e2b7f2b5608ee67c838b6500b2ae4a07ad52..034f0a5d7868fe956e3fc6a9b7ed485bb69caa04 100644
--- a/drivers/pci/pwrctrl/core.c
+++ b/drivers/pci/pwrctrl/core.c
@@ -10,16 +10,21 @@
 #include <linux/pci-pwrctrl.h>
 #include <linux/property.h>
 #include <linux/slab.h>
+#include "../pci.h"
 
 static int pci_pwrctrl_notify(struct notifier_block *nb, unsigned long action,
 			      void *data)
 {
 	struct pci_pwrctrl *pwrctrl = container_of(nb, struct pci_pwrctrl, nb);
 	struct device *dev = data;
+	struct pci_bus *bus = to_pci_dev(dev)->bus;
 
 	if (dev_fwnode(dev) != dev_fwnode(pwrctrl->dev))
 		return NOTIFY_DONE;
 
+	if (bus->self)
+		pcie_update_link_speed((struct pci_bus *)bus);
+
 	switch (action) {
 	case BUS_NOTIFY_ADD_DEVICE:
 		/*

-- 
2.34.1

Re: [PATCH v3 01/11] PCI: Update current bus speed as part of pci_pwrctrl_notify()

[Ilpo Järvinen]

On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:

> If the link is not up till the pwrctl drivers enable power to endpoints
> then cur_bus_speed will not be updated with correct speed.
> 
> As part of rescan, pci_pwrctrl_notify() will be called when new devices
> are added and as part of it update the link bus speed.
> 
> Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/pci/pwrctrl/core.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/pwrctrl/core.c b/drivers/pci/pwrctrl/core.c
> index 9cc7e2b7f2b5608ee67c838b6500b2ae4a07ad52..034f0a5d7868fe956e3fc6a9b7ed485bb69caa04 100644
> --- a/drivers/pci/pwrctrl/core.c
> +++ b/drivers/pci/pwrctrl/core.c
> @@ -10,16 +10,21 @@
>  #include <linux/pci-pwrctrl.h>
>  #include <linux/property.h>
>  #include <linux/slab.h>
> +#include "../pci.h"
>  
>  static int pci_pwrctrl_notify(struct notifier_block *nb, unsigned long action,
>  			      void *data)
>  {
>  	struct pci_pwrctrl *pwrctrl = container_of(nb, struct pci_pwrctrl, nb);
>  	struct device *dev = data;
> +	struct pci_bus *bus = to_pci_dev(dev)->bus;
>  
>  	if (dev_fwnode(dev) != dev_fwnode(pwrctrl->dev))
>  		return NOTIFY_DONE;
>  
> +	if (bus->self)
> +		pcie_update_link_speed((struct pci_bus *)bus);

Why are you casting here?? (Perhaps it's a leftover).

> +
>  	switch (action) {
>  	case BUS_NOTIFY_ADD_DEVICE:
>  		/*
> 
> 

-- 
 i.

Re: [PATCH v3 01/11] PCI: Update current bus speed as part of pci_pwrctrl_notify()

[Krishna Chaitanya Chundru]

On 5/19/2025 6:39 PM, Ilpo Järvinen wrote:
> On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:
> 
>> If the link is not up till the pwrctl drivers enable power to endpoints
>> then cur_bus_speed will not be updated with correct speed.
>>
>> As part of rescan, pci_pwrctrl_notify() will be called when new devices
>> are added and as part of it update the link bus speed.
>>
>> Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/pci/pwrctrl/core.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/pci/pwrctrl/core.c b/drivers/pci/pwrctrl/core.c
>> index 9cc7e2b7f2b5608ee67c838b6500b2ae4a07ad52..034f0a5d7868fe956e3fc6a9b7ed485bb69caa04 100644
>> --- a/drivers/pci/pwrctrl/core.c
>> +++ b/drivers/pci/pwrctrl/core.c
>> @@ -10,16 +10,21 @@
>>   #include <linux/pci-pwrctrl.h>
>>   #include <linux/property.h>
>>   #include <linux/slab.h>
>> +#include "../pci.h"
>>   
>>   static int pci_pwrctrl_notify(struct notifier_block *nb, unsigned long action,
>>   			      void *data)
>>   {
>>   	struct pci_pwrctrl *pwrctrl = container_of(nb, struct pci_pwrctrl, nb);
>>   	struct device *dev = data;
>> +	struct pci_bus *bus = to_pci_dev(dev)->bus;
>>   
>>   	if (dev_fwnode(dev) != dev_fwnode(pwrctrl->dev))
>>   		return NOTIFY_DONE;
>>   
>> +	if (bus->self)
>> +		pcie_update_link_speed((struct pci_bus *)bus);
> 
> Why are you casting here?? (Perhaps it's a leftover).
> 
yeah it is a leftover I will remove it in next patch.

- Krishna Chaitanya.
>> +
>>   	switch (action) {
>>   	case BUS_NOTIFY_ADD_DEVICE:
>>   		/*
>>
>>
> 

[PATCH v3 02/11] PCI/bwctrl: Add support to scale bandwidth before & after link re-training

[Krishna Chaitanya Chundru]

If the driver wants to move to higher data rate/speed than the current data
rate then the controller driver may need to change certain votes so that
link may come up at requested data rate/speed like QCOM PCIe controllers
need to change their RPMh (Resource Power Manager-hardened) state. Once
link retraining is done controller drivers needs to adjust their votes
based on the final data rate.

Some controllers also may need to update their bandwidth voting like
ICC bw votings etc.

So, add pre_scale_bus_bw() & post_scale_bus_bw() op to call before & after
the link re-train. There is no explicit locking mechanisms as these are
called by a single client endpoint driver.

In case of PCIe switch, if there is a request to change target speed for a
downstream port then no need to call these function ops as these are
outside the scope of the controller drivers.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pcie/bwctrl.c | 15 +++++++++++++++
 include/linux/pci.h       | 14 ++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index d8d2aa85a22928b99c5bba1d2bcc5647c0edeeb6..3525bc0cd10f1dd7794abbe84ccb10e2c53a10af 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -161,6 +161,8 @@ static int pcie_bwctrl_change_speed(struct pci_dev *port, u16 target_speed, bool
 int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
 			  bool use_lt)
 {
+	struct pci_host_bridge *host = pci_find_host_bridge(port->bus);
+	bool is_rootbus = pci_is_root_bus(port->bus);
 	struct pci_bus *bus = port->subordinate;
 	u16 target_speed;
 	int ret;
@@ -173,6 +175,16 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
 
 	target_speed = pcie_bwctrl_select_speed(port, speed_req);
 
+	/*
+	 * The host bridge driver may need to be scaled for targeted speed
+	 * otherwise link might not come up at requested speed.
+	 */
+	if (is_rootbus && host->pre_scale_bus_bw) {
+		ret = host->pre_scale_bus_bw(host, port, target_speed);
+		if (ret)
+			return ret;
+	}
+
 	scoped_guard(rwsem_read, &pcie_bwctrl_setspeed_rwsem) {
 		struct pcie_bwctrl_data *data = port->link_bwctrl;
 
@@ -197,6 +209,9 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
 	    !list_empty(&bus->devices))
 		ret = -EAGAIN;
 
+	if (bus && is_rootbus && host->post_scale_bus_bw)
+		host->post_scale_bus_bw(host, port, pci_bus_speed2lnkctl2(bus->cur_bus_speed));
+
 	return ret;
 }
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 51e2bd6405cda5acc33d268bbe1d491b145e083f..7eb0856ba0ed20bd1336683b68add124c7483902 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -601,6 +601,20 @@ struct pci_host_bridge {
 	void (*release_fn)(struct pci_host_bridge *);
 	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
 	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
+	/*
+	 * Callback to the host bridge drivers to update ICC bw votes, clock frequencies etc
+	 * for the link re-train to come up in targeted speed. These are intended to be
+	 * called by devices directly attached to the root port. These are called by a single
+	 * client endpoint driver, so there is no need for explicit locking mechanisms.
+	 */
+	int (*pre_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);
+	/*
+	 * Callback to the host bridge drivers to adjust ICC bw votes, clock frequencies etc
+	 * to the updated speed after link re-train. These are intended to be called by
+	 * devices directly attached to the root port. These are called by a single client
+	 * endpoint driver, so there is no need for explicit locking mechanisms.
+	 */
+	void (*post_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);
 	void		*release_data;
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */

-- 
2.34.1

Re: [PATCH v3 02/11] PCI/bwctrl: Add support to scale bandwidth before & after link re-training

[Ilpo Järvinen]

On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:

> If the driver wants to move to higher data rate/speed than the current data
> rate then the controller driver may need to change certain votes so that
> link may come up at requested data rate/speed like QCOM PCIe controllers
> need to change their RPMh (Resource Power Manager-hardened) state. Once
> link retraining is done controller drivers needs to adjust their votes
> based on the final data rate.
> 
> Some controllers also may need to update their bandwidth voting like
> ICC bw votings etc.
> 
> So, add pre_scale_bus_bw() & post_scale_bus_bw() op to call before & after
> the link re-train. There is no explicit locking mechanisms as these are
> called by a single client endpoint driver.
> 
> In case of PCIe switch, if there is a request to change target speed for a
> downstream port then no need to call these function ops as these are
> outside the scope of the controller drivers.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/pci/pcie/bwctrl.c | 15 +++++++++++++++
>  include/linux/pci.h       | 14 ++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
> index d8d2aa85a22928b99c5bba1d2bcc5647c0edeeb6..3525bc0cd10f1dd7794abbe84ccb10e2c53a10af 100644
> --- a/drivers/pci/pcie/bwctrl.c
> +++ b/drivers/pci/pcie/bwctrl.c
> @@ -161,6 +161,8 @@ static int pcie_bwctrl_change_speed(struct pci_dev *port, u16 target_speed, bool
>  int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>  			  bool use_lt)
>  {
> +	struct pci_host_bridge *host = pci_find_host_bridge(port->bus);
> +	bool is_rootbus = pci_is_root_bus(port->bus);
>  	struct pci_bus *bus = port->subordinate;
>  	u16 target_speed;
>  	int ret;
> @@ -173,6 +175,16 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>  
>  	target_speed = pcie_bwctrl_select_speed(port, speed_req);
>  
> +	/*
> +	 * The host bridge driver may need to be scaled for targeted speed
> +	 * otherwise link might not come up at requested speed.
> +	 */
> +	if (is_rootbus && host->pre_scale_bus_bw) {
> +		ret = host->pre_scale_bus_bw(host, port, target_speed);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	scoped_guard(rwsem_read, &pcie_bwctrl_setspeed_rwsem) {
>  		struct pcie_bwctrl_data *data = port->link_bwctrl;
>  
> @@ -197,6 +209,9 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>  	    !list_empty(&bus->devices))
>  		ret = -EAGAIN;
>  
> +	if (bus && is_rootbus && host->post_scale_bus_bw)
> +		host->post_scale_bus_bw(host, port, pci_bus_speed2lnkctl2(bus->cur_bus_speed));
> +
>  	return ret;
>  }
>  
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 51e2bd6405cda5acc33d268bbe1d491b145e083f..7eb0856ba0ed20bd1336683b68add124c7483902 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -601,6 +601,20 @@ struct pci_host_bridge {
>  	void (*release_fn)(struct pci_host_bridge *);
>  	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
>  	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
> +	/*
> +	 * Callback to the host bridge drivers to update ICC bw votes, clock frequencies etc

BW

> +	 * for the link re-train to come up in targeted speed. These are intended to be
> +	 * called by devices directly attached to the root port. These are called by a single

Root Port

> +	 * client endpoint driver, so there is no need for explicit locking mechanisms.

Endpoint

> +	 */
> +	int (*pre_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);
> +	/*
> +	 * Callback to the host bridge drivers to adjust ICC bw votes, clock frequencies etc
> +	 * to the updated speed after link re-train. These are intended to be called by
> +	 * devices directly attached to the root port. These are called by a single client
> +	 * endpoint driver, so there is no need for explicit locking mechanisms.
> +	 */

Please fold comments to 80 characters.

> +	void (*post_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);

I still don't like the names. Maybe simply pre/post_link_speed_change 
would sound more generic.

Not a show-stopper but the current name sounds pretty esoteric.

>  	void		*release_data;
>  	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
>  	unsigned int	no_ext_tags:1;		/* No Extended Tags */
> 
> 

-- 
 i.

Re: [PATCH v3 02/11] PCI/bwctrl: Add support to scale bandwidth before & after link re-training

[Krishna Chaitanya Chundru]

On 5/19/2025 7:11 PM, Ilpo Järvinen wrote:
> On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:
> 
>> If the driver wants to move to higher data rate/speed than the current data
>> rate then the controller driver may need to change certain votes so that
>> link may come up at requested data rate/speed like QCOM PCIe controllers
>> need to change their RPMh (Resource Power Manager-hardened) state. Once
>> link retraining is done controller drivers needs to adjust their votes
>> based on the final data rate.
>>
>> Some controllers also may need to update their bandwidth voting like
>> ICC bw votings etc.
>>
>> So, add pre_scale_bus_bw() & post_scale_bus_bw() op to call before & after
>> the link re-train. There is no explicit locking mechanisms as these are
>> called by a single client endpoint driver.
>>
>> In case of PCIe switch, if there is a request to change target speed for a
>> downstream port then no need to call these function ops as these are
>> outside the scope of the controller drivers.
>>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/pci/pcie/bwctrl.c | 15 +++++++++++++++
>>   include/linux/pci.h       | 14 ++++++++++++++
>>   2 files changed, 29 insertions(+)
>>
>> diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
>> index d8d2aa85a22928b99c5bba1d2bcc5647c0edeeb6..3525bc0cd10f1dd7794abbe84ccb10e2c53a10af 100644
>> --- a/drivers/pci/pcie/bwctrl.c
>> +++ b/drivers/pci/pcie/bwctrl.c
>> @@ -161,6 +161,8 @@ static int pcie_bwctrl_change_speed(struct pci_dev *port, u16 target_speed, bool
>>   int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>>   			  bool use_lt)
>>   {
>> +	struct pci_host_bridge *host = pci_find_host_bridge(port->bus);
>> +	bool is_rootbus = pci_is_root_bus(port->bus);
>>   	struct pci_bus *bus = port->subordinate;
>>   	u16 target_speed;
>>   	int ret;
>> @@ -173,6 +175,16 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>>   
>>   	target_speed = pcie_bwctrl_select_speed(port, speed_req);
>>   
>> +	/*
>> +	 * The host bridge driver may need to be scaled for targeted speed
>> +	 * otherwise link might not come up at requested speed.
>> +	 */
>> +	if (is_rootbus && host->pre_scale_bus_bw) {
>> +		ret = host->pre_scale_bus_bw(host, port, target_speed);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>>   	scoped_guard(rwsem_read, &pcie_bwctrl_setspeed_rwsem) {
>>   		struct pcie_bwctrl_data *data = port->link_bwctrl;
>>   
>> @@ -197,6 +209,9 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>>   	    !list_empty(&bus->devices))
>>   		ret = -EAGAIN;
>>   
>> +	if (bus && is_rootbus && host->post_scale_bus_bw)
>> +		host->post_scale_bus_bw(host, port, pci_bus_speed2lnkctl2(bus->cur_bus_speed));
>> +
>>   	return ret;
>>   }
>>   
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 51e2bd6405cda5acc33d268bbe1d491b145e083f..7eb0856ba0ed20bd1336683b68add124c7483902 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -601,6 +601,20 @@ struct pci_host_bridge {
>>   	void (*release_fn)(struct pci_host_bridge *);
>>   	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
>>   	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
>> +	/*
>> +	 * Callback to the host bridge drivers to update ICC bw votes, clock frequencies etc
> 
> BW
> 
>> +	 * for the link re-train to come up in targeted speed. These are intended to be
>> +	 * called by devices directly attached to the root port. These are called by a single
> 
> Root Port
> 
>> +	 * client endpoint driver, so there is no need for explicit locking mechanisms.
> 
> Endpoint
> 
>> +	 */
>> +	int (*pre_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);
>> +	/*
>> +	 * Callback to the host bridge drivers to adjust ICC bw votes, clock frequencies etc
>> +	 * to the updated speed after link re-train. These are intended to be called by
>> +	 * devices directly attached to the root port. These are called by a single client
>> +	 * endpoint driver, so there is no need for explicit locking mechanisms.
>> +	 */
> 
> Please fold comments to 80 characters.
> 
>> +	void (*post_scale_bus_bw)(struct pci_host_bridge *bridge, struct pci_dev *dev, int speed);
> 
> I still don't like the names. Maybe simply pre/post_link_speed_change
> would sound more generic.
>
Ack, I will change the name in the next patch.

- Krishna Chaitanya.

> Not a show-stopper but the current name sounds pretty esoteric.
> >>   	void		*release_data;
>>   	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
>>   	unsigned int	no_ext_tags:1;		/* No Extended Tags */
>>
>>
> 

[PATCH v3 03/11] PCI/ASPM: Return enabled ASPM states as part of pcie_aspm_enabled()

[Krishna Chaitanya Chundru]

PCIe ASPM states can be also controlled by userspace using exposed sysfs
entries, if drivers wants to disable and enable ASPM at runtime they
need to know enabled states for correctly enabling them back.

So return the enabled aspm states as part of pcie_aspm_enabled().

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pcie/aspm.c | 4 +++-
 include/linux/pci.h     | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 29fcb0689a918f9cb123691e1680de5a1af2c115..94324fc0d3e650cd3ca2c0bb8c1895ca7e647b9d 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1555,8 +1555,10 @@ module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
  * is deallocated only when the last child of the bridge (i.e., @pdev or a
  * sibling) is removed, and the caller should be holding a reference to
  * @pdev, so this should be safe.
+ *
+ * Return: Enabled ASPM states
  */
-bool pcie_aspm_enabled(struct pci_dev *pdev)
+int pcie_aspm_enabled(struct pci_dev *pdev)
 {
 	struct pcie_link_state *link = pcie_aspm_get_link(pdev);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 7eb0856ba0ed20bd1336683b68add124c7483902..ce9d0812a61c2337ba533ef246393a0101e617ee 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1849,7 +1849,7 @@ int pci_enable_link_state(struct pci_dev *pdev, int state);
 int pci_enable_link_state_locked(struct pci_dev *pdev, int state);
 void pcie_no_aspm(void);
 bool pcie_aspm_support_enabled(void);
-bool pcie_aspm_enabled(struct pci_dev *pdev);
+int pcie_aspm_enabled(struct pci_dev *pdev);
 #else
 static inline int pci_disable_link_state(struct pci_dev *pdev, int state)
 { return 0; }
@@ -1861,7 +1861,7 @@ static inline int pci_enable_link_state_locked(struct pci_dev *pdev, int state)
 { return 0; }
 static inline void pcie_no_aspm(void) { }
 static inline bool pcie_aspm_support_enabled(void) { return false; }
-static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; }
+static inline int pcie_aspm_enabled(struct pci_dev *pdev) { return false; }
 #endif
 
 #ifdef CONFIG_PCIEAER

-- 
2.34.1

[PATCH v3 04/11] PCI/ASPM: Clear aspm_disable as part of __pci_enable_link_state()

[Krishna Chaitanya Chundru]

If a driver wants to enable ASPM back after disabling ASPM for some
usecase, it is not being enabled properly because of the aspm_disable
flag is not getting cleared. This flag is being properly when aspm
is controlled by sysfs.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pcie/aspm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 94324fc0d3e650cd3ca2c0bb8c1895ca7e647b9d..0f858ef86111b43328bc7db01e6493ce67178458 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1453,6 +1453,7 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
 		down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
 	link->aspm_default = pci_calc_aspm_enable_mask(state);
+	link->aspm_disable &= ~state;
 	pcie_config_aspm_link(link, policy_to_aspm_state(link));
 
 	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;

-- 
2.34.1

Re: [PATCH v3 04/11] PCI/ASPM: Clear aspm_disable as part of __pci_enable_link_state()

[Ilpo Järvinen]

On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:

> If a driver wants to enable ASPM back after disabling ASPM for some
> usecase, it is not being enabled properly because of the aspm_disable
> flag is not getting cleared. This flag is being properly when aspm
> is controlled by sysfs.

This sentence has broken grammar/is missing something?

aspm -> ASPM

> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/pci/pcie/aspm.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 94324fc0d3e650cd3ca2c0bb8c1895ca7e647b9d..0f858ef86111b43328bc7db01e6493ce67178458 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -1453,6 +1453,7 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
>  		down_read(&pci_bus_sem);
>  	mutex_lock(&aspm_lock);
>  	link->aspm_default = pci_calc_aspm_enable_mask(state);
> +	link->aspm_disable &= ~state;
>  	pcie_config_aspm_link(link, policy_to_aspm_state(link));
>  
>  	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;

I disagree with this change.

The problem currently with ASPM driver is that pci_disable_link_state() 
and pci_enable_link_state() are not symmetric pairs despite their 
misleading names. pci_enable_link_state() should be renamed to 
pci_set_default_link_state() and if the symmetric pair is needed for 
pci_disable_link_state(), it would have to be added separately.

I've some (rotting) patches which try to do that, in case you want to try 
to solve this inconsistency in the ASPM driver (I can send them to you)?

-- 
 i.

Re: [PATCH v3 04/11] PCI/ASPM: Clear aspm_disable as part of __pci_enable_link_state()

[Krishna Chaitanya Chundru]

On 5/19/2025 6:51 PM, Ilpo Järvinen wrote:
> On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:
> 
>> If a driver wants to enable ASPM back after disabling ASPM for some
>> usecase, it is not being enabled properly because of the aspm_disable
>> flag is not getting cleared. This flag is being properly when aspm
>> is controlled by sysfs.
> 
> This sentence has broken grammar/is missing something?
> 
> aspm -> ASPM
> 
>>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/pci/pcie/aspm.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>> index 94324fc0d3e650cd3ca2c0bb8c1895ca7e647b9d..0f858ef86111b43328bc7db01e6493ce67178458 100644
>> --- a/drivers/pci/pcie/aspm.c
>> +++ b/drivers/pci/pcie/aspm.c
>> @@ -1453,6 +1453,7 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
>>   		down_read(&pci_bus_sem);
>>   	mutex_lock(&aspm_lock);
>>   	link->aspm_default = pci_calc_aspm_enable_mask(state);
>> +	link->aspm_disable &= ~state;
>>   	pcie_config_aspm_link(link, policy_to_aspm_state(link));
>>   
>>   	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;
> 
> I disagree with this change.
> 
> The problem currently with ASPM driver is that pci_disable_link_state()
> and pci_enable_link_state() are not symmetric pairs despite their
> misleading names. pci_enable_link_state() should be renamed to
> pci_set_default_link_state() and if the symmetric pair is needed for
> pci_disable_link_state(), it would have to be added separately.
> 
I just want to know what are disadvantages/side effects having this
change here, we can use same API to be symmetric with 
pci_disable_link_state(). The drivers which are using this API has
already option to specific the ASPM states which they want to enable and 
they don't need to call pci_disable_link_state() to specify the states
they want to disable.

- Krishna Chaitanya.
> I've some (rotting) patches which try to do that, in case you want to try
> to solve this inconsistency in the ASPM driver (I can send them to you)?
> 

[PATCH v3 05/11] PCI: qcom: Extract core logic from qcom_pcie_icc_opp_update()

[Krishna Chaitanya Chundru]

Extract core logic from qcom_pcie_icc_opp_update() into
qcom_pcie_set_icc_opp() to use in other parts of the code to avoid
duplications.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 61 +++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 26 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index dc98ae63362db0422384b1879a2b9a7dc564d091..bd984cde8d3bd688b2ac32566b0e9cdbc70905c0 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1294,6 +1294,40 @@ static void qcom_pcie_host_post_init(struct dw_pcie_rp *pp)
 		pcie->cfg->ops->host_post_init(pcie);
 }
 
+static int qcom_pcie_set_icc_opp(struct qcom_pcie *pcie, int speed, int width)
+{
+	struct dw_pcie *pci = pcie->pci;
+	unsigned long freq_kbps;
+	struct dev_pm_opp *opp;
+	int ret = 0, freq_mbps;
+
+	if (pcie->icc_mem) {
+		ret = icc_set_bw(pcie->icc_mem, 0,
+				 width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
+		if (ret) {
+			dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
+				ret);
+		}
+	} else if (pcie->use_pm_opp) {
+		freq_mbps = pcie_dev_speed_mbps(pcie_link_speed[speed]);
+		if (freq_mbps < 0)
+			return -EINVAL;
+
+		freq_kbps = freq_mbps * KILO;
+		opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * width,
+						 true);
+		if (!IS_ERR(opp)) {
+			ret = dev_pm_opp_set_opp(pci->dev, opp);
+			if (ret)
+				dev_err(pci->dev, "Failed to set OPP for freq (%lu): %d\n",
+					freq_kbps * width, ret);
+			dev_pm_opp_put(opp);
+		}
+	}
+
+	return ret;
+}
+
 static const struct dw_pcie_host_ops qcom_pcie_dw_ops = {
 	.init		= qcom_pcie_host_init,
 	.deinit		= qcom_pcie_host_deinit,
@@ -1478,9 +1512,6 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
 {
 	u32 offset, status, width, speed;
 	struct dw_pcie *pci = pcie->pci;
-	unsigned long freq_kbps;
-	struct dev_pm_opp *opp;
-	int ret, freq_mbps;
 
 	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
 	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
@@ -1492,29 +1523,7 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
 	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
 	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
 
-	if (pcie->icc_mem) {
-		ret = icc_set_bw(pcie->icc_mem, 0,
-				 width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
-		if (ret) {
-			dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
-				ret);
-		}
-	} else if (pcie->use_pm_opp) {
-		freq_mbps = pcie_dev_speed_mbps(pcie_link_speed[speed]);
-		if (freq_mbps < 0)
-			return;
-
-		freq_kbps = freq_mbps * KILO;
-		opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * width,
-						 true);
-		if (!IS_ERR(opp)) {
-			ret = dev_pm_opp_set_opp(pci->dev, opp);
-			if (ret)
-				dev_err(pci->dev, "Failed to set OPP for freq (%lu): %d\n",
-					freq_kbps * width, ret);
-			dev_pm_opp_put(opp);
-		}
-	}
+	qcom_pcie_set_icc_opp(pcie, speed, width);
 }
 
 static int qcom_pcie_link_transition_count(struct seq_file *s, void *data)

-- 
2.34.1

[PATCH v3 06/11] PCI: qcom: Add support for PCIe bus bw scaling

[Krishna Chaitanya Chundru]

QCOM PCIe controllers need to disable ASPM before initiating link
re-train. So as part of pre_bw_scale() disable ASPM and as part of
post_scale_bus_bw() enable ASPM back.

As the driver needs to enable the ASPM states that are enabled
by the system, save PCI ASPM states before disabling them and
in post_scale_bus_bw() use the saved ASPM states to enable
back the ASPM.

Update ICC & OPP votes based on the requested speed so that RPMh votes
get updated based on the speed.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 63 ++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index bd984cde8d3bd688b2ac32566b0e9cdbc70905c0..491324d44785535b84460d468727b8c356ca1040 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -276,10 +276,16 @@ struct qcom_pcie {
 	struct dentry *debugfs;
 	bool suspended;
 	bool use_pm_opp;
+	int aspm_state; /* Store ASPM state used in pre & post scale bus bw */
 };
 
 #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
 
+static void qcom_pcie_host_post_scale_bus_bw(struct pci_host_bridge *bridge,
+					     struct pci_dev *pdev, int current_speed);
+static int qcom_pcie_host_pre_scale_bus_bw(struct pci_host_bridge *bridge,
+					   struct pci_dev *pdev, int current_speed);
+
 static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
 {
 	gpiod_set_value_cansleep(pcie->reset, 1);
@@ -1263,6 +1269,8 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 			goto err_assert_reset;
 	}
 
+	pp->bridge->pre_scale_bus_bw = qcom_pcie_host_pre_scale_bus_bw;
+	pp->bridge->post_scale_bus_bw = qcom_pcie_host_post_scale_bus_bw;
 	return 0;
 
 err_assert_reset:
@@ -1328,6 +1336,61 @@ static int qcom_pcie_set_icc_opp(struct qcom_pcie *pcie, int speed, int width)
 	return ret;
 }
 
+static int qcom_pcie_scale_bw(struct dw_pcie_rp *pp, int speed)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+	u32 offset, status, width;
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
+
+	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
+
+	return qcom_pcie_set_icc_opp(pcie, speed, width);
+}
+
+static void qcom_pcie_host_post_scale_bus_bw(struct pci_host_bridge *bridge,
+					     struct pci_dev *pdev, int current_speed)
+{
+	struct dw_pcie_rp *pp = bridge->bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+	struct pci_dev *child;
+
+	/* Get function 0 of downstream device */
+	list_for_each_entry(child, &pdev->subordinate->devices, bus_list)
+		if (PCI_FUNC(child->devfn) == 0)
+			break;
+
+	pci_enable_link_state_locked(child, pcie->aspm_state);
+
+	qcom_pcie_scale_bw(pp, current_speed);
+}
+
+static int qcom_pcie_host_pre_scale_bus_bw(struct pci_host_bridge *bridge,
+					   struct pci_dev *pdev, int target_speed)
+{
+	struct dw_pcie_rp *pp = bridge->bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+	struct pci_dev *child;
+
+	/* Get function 0 of downstream device */
+	list_for_each_entry(child, &pdev->subordinate->devices, bus_list)
+		if (PCI_FUNC(child->devfn) == 0)
+			break;
+	/*
+	 * QCOM controllers doesn't support link re-train with ASPM enabled.
+	 * Disable ASPM as part of pre_bus_bw() and enable them back as
+	 * part of post_bus_bw().
+	 */
+	pcie->aspm_state = pcie_aspm_enabled(child);
+	pci_disable_link_state_locked(child, PCIE_LINK_STATE_ALL);
+
+	return qcom_pcie_scale_bw(pp, target_speed);
+}
+
 static const struct dw_pcie_host_ops qcom_pcie_dw_ops = {
 	.init		= qcom_pcie_host_init,
 	.deinit		= qcom_pcie_host_deinit,

-- 
2.34.1

[PATCH v3 07/11] bus: mhi: host: Add support to read MHI capabilities

[Krishna Chaitanya Chundru]

From: Vivek Pernamitta <quic_vpernami@quicinc.com>

As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
located after the ERDB array. The location of this group of registers is
indicated by the MISCOFF register. Each capability has a capability ID to
determine which functionality is supported and each capability will point
to the next capability supported.

Add a basic function to read those capabilities offsets.

Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/bus/mhi/common.h    |  4 ++++
 drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
index dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
--- a/drivers/bus/mhi/common.h
+++ b/drivers/bus/mhi/common.h
@@ -16,6 +16,7 @@
 #define MHICFG				0x10
 #define CHDBOFF				0x18
 #define ERDBOFF				0x20
+#define MISCOFF				0x24
 #define BHIOFF				0x28
 #define BHIEOFF				0x2c
 #define DEBUGOFF			0x30
@@ -113,6 +114,9 @@
 #define MHISTATUS_MHISTATE_MASK		GENMASK(15, 8)
 #define MHISTATUS_SYSERR_MASK		BIT(2)
 #define MHISTATUS_READY_MASK		BIT(0)
+#define MISC_CAP_MASK			GENMASK(31, 0)
+#define CAP_CAPID_MASK			GENMASK(31, 24)
+#define CAP_NEXT_CAP_MASK		GENMASK(23, 12)
 
 /* Command Ring Element macros */
 /* No operation command */
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -467,6 +467,35 @@ int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)
 	return ret;
 }
 
+static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability, u32 *offset)
+{
+	u32 val, cur_cap, next_offset;
+	int ret;
+
+	/* Get the 1st supported capability offset */
+	ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
+				 MISC_CAP_MASK, offset);
+	if (ret)
+		return ret;
+	do {
+		if (*offset >= mhi_cntrl->reg_len)
+			return -ENXIO;
+
+		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
+		if (ret)
+			return ret;
+
+		cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
+		next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
+		if (cur_cap == capability)
+			return 0;
+
+		*offset = next_offset;
+	} while (next_offset);
+
+	return -ENXIO;
+}
+
 int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 {
 	u32 val;

-- 
2.34.1

Re: [PATCH v3 07/11] bus: mhi: host: Add support to read MHI capabilities

[Jeffrey Hugo]

On 5/19/2025 3:42 AM, Krishna Chaitanya Chundru wrote:
> From: Vivek Pernamitta <quic_vpernami@quicinc.com>
> 
> As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
> located after the ERDB array. The location of this group of registers is
> indicated by the MISCOFF register. Each capability has a capability ID to
> determine which functionality is supported and each capability will point
> to the next capability supported.
> 
> Add a basic function to read those capabilities offsets.
> 
> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>   drivers/bus/mhi/common.h    |  4 ++++
>   drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
>   2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> index dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
> --- a/drivers/bus/mhi/common.h
> +++ b/drivers/bus/mhi/common.h
> @@ -16,6 +16,7 @@
>   #define MHICFG				0x10
>   #define CHDBOFF				0x18
>   #define ERDBOFF				0x20
> +#define MISCOFF				0x24
>   #define BHIOFF				0x28
>   #define BHIEOFF				0x2c
>   #define DEBUGOFF			0x30
> @@ -113,6 +114,9 @@
>   #define MHISTATUS_MHISTATE_MASK		GENMASK(15, 8)
>   #define MHISTATUS_SYSERR_MASK		BIT(2)
>   #define MHISTATUS_READY_MASK		BIT(0)
> +#define MISC_CAP_MASK			GENMASK(31, 0)
> +#define CAP_CAPID_MASK			GENMASK(31, 24)
> +#define CAP_NEXT_CAP_MASK		GENMASK(23, 12)
>   
>   /* Command Ring Element macros */
>   /* No operation command */
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -467,6 +467,35 @@ int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)
>   	return ret;
>   }
>   
> +static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability, u32 *offset)
> +{
> +	u32 val, cur_cap, next_offset;
> +	int ret;
> +
> +	/* Get the 1st supported capability offset */

"first"?  Does not seem like you are short on space here.

> +	ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
> +				 MISC_CAP_MASK, offset);

This fits on one line.

> +	if (ret)
> +		return ret;

Blank line here would be nice.

> +	do {
> +		if (*offset >= mhi_cntrl->reg_len)
> +			return -ENXIO;
> +
> +		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
> +		if (ret)
> +			return ret;


There is no sanity checking we can do on val?  We've had plenty of 
issues blindly trusting the device.  I would like to avoid having more.

Also looks like if we find the capability we are looking for, we return 
the offset without validating it.

> +
> +		cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
> +		next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
> +		if (cur_cap == capability)
> +			return 0;
> +
> +		*offset = next_offset;
> +	} while (next_offset);
> +
> +	return -ENXIO;
> +}
> +
>   int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>   {
>   	u32 val;
> 

Re: [PATCH v3 07/11] bus: mhi: host: Add support to read MHI capabilities

[Krishna Chaitanya Chundru]

On 5/21/2025 8:22 PM, Jeffrey Hugo wrote:
> On 5/19/2025 3:42 AM, Krishna Chaitanya Chundru wrote:
>> From: Vivek Pernamitta <quic_vpernami@quicinc.com>
>>
>> As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
>> located after the ERDB array. The location of this group of registers is
>> indicated by the MISCOFF register. Each capability has a capability ID to
>> determine which functionality is supported and each capability will point
>> to the next capability supported.
>>
>> Add a basic function to read those capabilities offsets.
>>
>> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
>> Signed-off-by: Krishna Chaitanya Chundru 
>> <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/bus/mhi/common.h    |  4 ++++
>>   drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
>>   2 files changed, 33 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
>> index 
>> dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
>> --- a/drivers/bus/mhi/common.h
>> +++ b/drivers/bus/mhi/common.h
>> @@ -16,6 +16,7 @@
>>   #define MHICFG                0x10
>>   #define CHDBOFF                0x18
>>   #define ERDBOFF                0x20
>> +#define MISCOFF                0x24
>>   #define BHIOFF                0x28
>>   #define BHIEOFF                0x2c
>>   #define DEBUGOFF            0x30
>> @@ -113,6 +114,9 @@
>>   #define MHISTATUS_MHISTATE_MASK        GENMASK(15, 8)
>>   #define MHISTATUS_SYSERR_MASK        BIT(2)
>>   #define MHISTATUS_READY_MASK        BIT(0)
>> +#define MISC_CAP_MASK            GENMASK(31, 0)
>> +#define CAP_CAPID_MASK            GENMASK(31, 24)
>> +#define CAP_NEXT_CAP_MASK        GENMASK(23, 12)
>>   /* Command Ring Element macros */
>>   /* No operation command */
>> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
>> index 
>> 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
>> --- a/drivers/bus/mhi/host/init.c
>> +++ b/drivers/bus/mhi/host/init.c
>> @@ -467,6 +467,35 @@ int mhi_init_dev_ctxt(struct mhi_controller 
>> *mhi_cntrl)
>>       return ret;
>>   }
>> +static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 
>> capability, u32 *offset)
>> +{
>> +    u32 val, cur_cap, next_offset;
>> +    int ret;
>> +
>> +    /* Get the 1st supported capability offset */
> 
> "first"?  Does not seem like you are short on space here.
> 
Misc register will have the offest of the 1st capability register
from there capabilities will have linked list format.
>> +    ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
>> +                 MISC_CAP_MASK, offset);
> 
> This fits on one line.
> 
>> +    if (ret)
>> +        return ret;
> 
> Blank line here would be nice.
> 
>> +    do {
>> +        if (*offset >= mhi_cntrl->reg_len)
>> +            return -ENXIO;
>> +
>> +        ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
>> +        if (ret)
>> +            return ret;
> 
> 
> There is no sanity checking we can do on val?  We've had plenty of 
> issues blindly trusting the device.  I would like to avoid having more.
> 
we can check if val is not all F's as sanity other than that we can't
check any other things as we don't know if the value is valid or not.
Let me know if you have any taught on this.
> Also looks like if we find the capability we are looking for, we return 
> the offset without validating it.
> 
For offset I can have a check to make sure the offset is not crossing
mhi reg len like above.

- Krishna Chaitanya.
>> +
>> +        cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
>> +        next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
>> +        if (cur_cap == capability)
>> +            return 0;
>> +
>> +        *offset = next_offset;
>> +    } while (next_offset);
>> +
>> +    return -ENXIO;
>> +}
>> +
>>   int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>>   {
>>       u32 val;
>>
> 

Re: [PATCH v3 07/11] bus: mhi: host: Add support to read MHI capabilities

[Jeffrey Hugo]

On 5/21/2025 9:06 AM, Krishna Chaitanya Chundru wrote:
> 
> 
> On 5/21/2025 8:22 PM, Jeffrey Hugo wrote:
>> On 5/19/2025 3:42 AM, Krishna Chaitanya Chundru wrote:
>>> From: Vivek Pernamitta <quic_vpernami@quicinc.com>
>>>
>>> As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
>>> located after the ERDB array. The location of this group of registers is
>>> indicated by the MISCOFF register. Each capability has a capability 
>>> ID to
>>> determine which functionality is supported and each capability will 
>>> point
>>> to the next capability supported.
>>>
>>> Add a basic function to read those capabilities offsets.
>>>
>>> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
>>> Signed-off-by: Krishna Chaitanya Chundru 
>>> <krishna.chundru@oss.qualcomm.com>
>>> ---
>>>   drivers/bus/mhi/common.h    |  4 ++++
>>>   drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
>>>   2 files changed, 33 insertions(+)
>>>
>>> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
>>> index 
>>> dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
>>> --- a/drivers/bus/mhi/common.h
>>> +++ b/drivers/bus/mhi/common.h
>>> @@ -16,6 +16,7 @@
>>>   #define MHICFG                0x10
>>>   #define CHDBOFF                0x18
>>>   #define ERDBOFF                0x20
>>> +#define MISCOFF                0x24
>>>   #define BHIOFF                0x28
>>>   #define BHIEOFF                0x2c
>>>   #define DEBUGOFF            0x30
>>> @@ -113,6 +114,9 @@
>>>   #define MHISTATUS_MHISTATE_MASK        GENMASK(15, 8)
>>>   #define MHISTATUS_SYSERR_MASK        BIT(2)
>>>   #define MHISTATUS_READY_MASK        BIT(0)
>>> +#define MISC_CAP_MASK            GENMASK(31, 0)
>>> +#define CAP_CAPID_MASK            GENMASK(31, 24)
>>> +#define CAP_NEXT_CAP_MASK        GENMASK(23, 12)
>>>   /* Command Ring Element macros */
>>>   /* No operation command */
>>> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
>>> index 
>>> 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
>>> --- a/drivers/bus/mhi/host/init.c
>>> +++ b/drivers/bus/mhi/host/init.c
>>> @@ -467,6 +467,35 @@ int mhi_init_dev_ctxt(struct mhi_controller 
>>> *mhi_cntrl)
>>>       return ret;
>>>   }
>>> +static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 
>>> capability, u32 *offset)
>>> +{
>>> +    u32 val, cur_cap, next_offset;
>>> +    int ret;
>>> +
>>> +    /* Get the 1st supported capability offset */
>>
>> "first"?  Does not seem like you are short on space here.
>>
> Misc register will have the offest of the 1st capability register
> from there capabilities will have linked list format.

No, I'm saying don't have "1st" in the comment, but have "first" 
instead. I think that will read better.

"Get the first supported capability offset"

>>> +    ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
>>> +                 MISC_CAP_MASK, offset);
>>
>> This fits on one line.
>>
>>> +    if (ret)
>>> +        return ret;
>>
>> Blank line here would be nice.
>>
>>> +    do {
>>> +        if (*offset >= mhi_cntrl->reg_len)
>>> +            return -ENXIO;
>>> +
>>> +        ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
>>> +        if (ret)
>>> +            return ret;
>>
>>
>> There is no sanity checking we can do on val?  We've had plenty of 
>> issues blindly trusting the device.  I would like to avoid having more.
>>
> we can check if val is not all F's as sanity other than that we can't
> check any other things as we don't know if the value is valid or not.
> Let me know if you have any taught on this.

mhi_read_reg() should handle the PCIe link error case. You can check to 
see that the value is within the MHI space before using it.

Also, shouldn't the value be transformed from le32 to cpu and back?

>> Also looks like if we find the capability we are looking for, we 
>> return the offset without validating it.
>>
> For offset I can have a check to make sure the offset is not crossing
> mhi reg len like above.
> 
> - Krishna Chaitanya.
>>> +
>>> +        cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
>>> +        next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
>>> +        if (cur_cap == capability)
>>> +            return 0;
>>> +
>>> +        *offset = next_offset;
>>> +    } while (next_offset);
>>> +
>>> +    return -ENXIO;
>>> +}
>>> +
>>>   int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>>>   {
>>>       u32 val;
>>>
>>

[PATCH v3 08/11] bus: mhi: host: Add support for Bandwidth scale

[Krishna Chaitanya Chundru]

As per MHI spec v1.2, sec 14, MHI supports bandwidth scaling to reduce
power consumption. MHI bandwidth scaling is advertised by devices that
contain the bandwidth scaling capability registers. If enabled, the device
aggregates bandwidth requirements and sends them to the host through
dedicated mhi event ring. After the host performs the bandwidth switch,
it sends an acknowledgment by ringing a doorbell.

if the host supports bandwidth scaling events, then it must set
BW_CFG.ENABLED bit, set BW_CFG.DB_CHAN_ID to the channel ID to the
doorbell that will be used by the host to communicate the bandwidth
scaling status and BW_CFG.ER_INDEX to the index for the event ring
to which the device should send bandwidth scaling request in the
bandwidth scaling capability register.

As part of mmio init check if the bw scale capability is present or not,
if present advertise host supports bw scale by setting all the required
fields.

MHI layer will only forward the bw scaling request to the controller
driver since MHI doesn't have any idea about transport layer used by
the controller, it is responsibility of the controller driver to do actual
bw scaling and then pass status to the MHI. MHI will response back to the
device based up on the status of the bw scale received.

Add a new get_misc_doorbell() to get doorbell for misc capabilities to
use the doorbell with mhi events like MHI BW scale etc.

Use workqueue & mutex for the bw scale events as the pci_set_target_speed()
which will called by the mhi controller driver can sleep.

Co-developed-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/bus/mhi/common.h        | 16 +++++++
 drivers/bus/mhi/host/init.c     | 61 ++++++++++++++++++++++++-
 drivers/bus/mhi/host/internal.h |  7 ++-
 drivers/bus/mhi/host/main.c     | 98 ++++++++++++++++++++++++++++++++++++++++-
 drivers/bus/mhi/host/pm.c       | 10 ++++-
 include/linux/mhi.h             | 13 ++++++
 6 files changed, 199 insertions(+), 6 deletions(-)

diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
index eedac801b80021e44f7c65d33cd50760e06c02f2..0a02acee709af7a2a6abddcb9547ef56564ce453 100644
--- a/drivers/bus/mhi/common.h
+++ b/drivers/bus/mhi/common.h
@@ -208,6 +208,22 @@
 #define MHI_RSCTRE_DATA_DWORD1		cpu_to_le32(FIELD_PREP(GENMASK(23, 16), \
 							       MHI_PKT_TYPE_COALESCING))
 
+/* MHI Bandwidth scaling offsets */
+#define MHI_BW_SCALE_CFG_OFFSET		0x4
+#define MHI_BW_SCALE_CAP_ID		(3)
+
+#define MHI_BW_SCALE_ENABLE(bw_scale_db, er_index)	cpu_to_le32(FIELD_PREP(GENMASK(31, 25), \
+							bw_scale_db) |				\
+							FIELD_PREP(GENMASK(23, 19), er_index) |	\
+							BIT(24))
+
+#define MHI_TRE_GET_EV_BW_REQ_SEQ(tre)	FIELD_GET(GENMASK(15, 8), (MHI_TRE_GET_DWORD(tre, 0)))
+#define MHI_BW_SCALE_DB_ID(er_index)	FIELD_PREP(GENMASK(31, 25), er_index)
+
+#define MHI_BW_SCALE_RESULT(status, seq)	cpu_to_le32(FIELD_PREP(GENMASK(11, 8), status) | \
+						FIELD_PREP(GENMASK(7, 0), seq))
+#define MHI_BW_SCALE_NACK			0xF
+
 enum mhi_pkt_type {
 	MHI_PKT_TYPE_INVALID = 0x0,
 	MHI_PKT_TYPE_NOOP_CMD = 0x1,
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index a7137a040bdce1c58c98fe9c2340aae4cc4387d1..9fe6020f7868ec8bd114d0d96edc9d17624cbac5 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -496,10 +496,53 @@ static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability,
 	return -ENXIO;
 }
 
+static int mhi_get_er_index(struct mhi_controller *mhi_cntrl,
+			    enum mhi_er_data_type type)
+{
+	struct mhi_event *mhi_event = mhi_cntrl->mhi_event;
+	int i;
+
+	/* Find event ring for requested type */
+	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
+		if (mhi_event->data_type == type)
+			return mhi_event->er_index;
+	}
+
+	return -ENOENT;
+}
+
+static int mhi_init_bw_scale(struct mhi_controller *mhi_cntrl,
+			     int bw_scale_db)
+{
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	int ret, er_index, val;
+	u32 bw_cfg_offset;
+
+	ret = mhi_find_capability(mhi_cntrl, MHI_BW_SCALE_CAP_ID, &bw_cfg_offset);
+	if (ret)
+		return ret;
+
+	er_index = mhi_get_er_index(mhi_cntrl, MHI_ER_BW_SCALE);
+	if (er_index < 0)
+		return er_index;
+
+	bw_cfg_offset += MHI_BW_SCALE_CFG_OFFSET;
+
+	/* Advertise host support */
+	val = MHI_BW_SCALE_ENABLE(bw_scale_db, er_index);
+
+	mhi_write_reg(mhi_cntrl, mhi_cntrl->regs, bw_cfg_offset, val);
+
+	dev_dbg(dev, "Bandwidth scaling setup complete with event ring: %d\n",
+		er_index);
+
+	return 0;
+}
+
 int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 {
 	u32 val;
-	int i, ret;
+	int i, ret, doorbell = 0;
 	struct mhi_chan *mhi_chan;
 	struct mhi_event *mhi_event;
 	void __iomem *base = mhi_cntrl->regs;
@@ -633,6 +676,16 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 		return ret;
 	}
 
+	if (mhi_cntrl->get_misc_doorbell)
+		doorbell = mhi_cntrl->get_misc_doorbell(mhi_cntrl, MHI_ER_BW_SCALE);
+
+	if (doorbell > 0) {
+		ret = mhi_init_bw_scale(mhi_cntrl, doorbell);
+		if (!ret)
+			mhi_cntrl->bw_scale_db = base + val + (8 * doorbell);
+		else
+			dev_warn(dev, "Failed to setup bandwidth scaling: %d\n", ret);
+	}
 	return 0;
 }
 
@@ -778,6 +831,9 @@ static int parse_ev_cfg(struct mhi_controller *mhi_cntrl,
 		case MHI_ER_CTRL:
 			mhi_event->process_event = mhi_process_ctrl_ev_ring;
 			break;
+		case MHI_ER_BW_SCALE:
+			mhi_event->process_event = mhi_process_bw_scale_ev_ring;
+			break;
 		default:
 			dev_err(dev, "Event Ring type not supported\n");
 			goto error_ev_cfg;
@@ -1012,9 +1068,12 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 
 		mhi_event->mhi_cntrl = mhi_cntrl;
 		spin_lock_init(&mhi_event->lock);
+		mutex_init(&mhi_event->mutex);
 		if (mhi_event->data_type == MHI_ER_CTRL)
 			tasklet_init(&mhi_event->task, mhi_ctrl_ev_task,
 				     (ulong)mhi_event);
+		else if (mhi_event->data_type == MHI_ER_BW_SCALE)
+			INIT_WORK(&mhi_event->work, mhi_process_ev_work);
 		else
 			tasklet_init(&mhi_event->task, mhi_ev_task,
 				     (ulong)mhi_event);
diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
index ce566f7d2e9240c64044407aa4124ad3cdb98003..cf64adaecad2aeec8569da5276ec60dd7e97e5e0 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -248,6 +248,8 @@ struct mhi_event {
 	struct mhi_ring ring;
 	struct db_cfg db_cfg;
 	struct tasklet_struct task;
+	struct work_struct work;
+	struct mutex mutex; /* lock for synchronization */
 	spinlock_t lock;
 	int (*process_event)(struct mhi_controller *mhi_cntrl,
 			     struct mhi_event *mhi_event,
@@ -410,7 +412,8 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
 				struct mhi_event *mhi_event, u32 event_quota);
 int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
 			     struct mhi_event *mhi_event, u32 event_quota);
-
+int mhi_process_bw_scale_ev_ring(struct mhi_controller *mhi_cntrl,
+				 struct mhi_event *mhi_event, u32 event_quota);
 /* ISR handlers */
 irqreturn_t mhi_irq_handler(int irq_number, void *dev);
 irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *dev);
@@ -426,5 +429,5 @@ void mhi_unmap_single_no_bb(struct mhi_controller *mhi_cntrl,
 			    struct mhi_buf_info *buf_info);
 void mhi_unmap_single_use_bb(struct mhi_controller *mhi_cntrl,
 			     struct mhi_buf_info *buf_info);
-
+void mhi_process_ev_work(struct work_struct *work);
 #endif /* _MHI_INT_H */
diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 9bb0df43ceef1e54e8817422516aab1def6fdc4a..f87e9550b59227947fc7268c5799eea274c66b98 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -472,7 +472,10 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
 		if (mhi_dev)
 			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
 	} else {
-		tasklet_schedule(&mhi_event->task);
+		if (mhi_event->data_type == MHI_ER_BW_SCALE)
+			queue_work(mhi_cntrl->hiprio_wq, &mhi_event->work);
+		else
+			tasklet_schedule(&mhi_event->task);
 	}
 
 	return IRQ_HANDLED;
@@ -1049,6 +1052,99 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
 	return count;
 }
 
+int mhi_process_bw_scale_ev_ring(struct mhi_controller *mhi_cntrl,
+				 struct mhi_event *mhi_event, u32 event_quota)
+{
+	struct mhi_event_ctxt *er_ctxt = &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	struct mhi_ring *ev_ring = &mhi_event->ring;
+	dma_addr_t ptr = le64_to_cpu(er_ctxt->rp);
+	u32 response = MHI_BW_SCALE_NACK;
+	struct mhi_ring_element *dev_rp;
+	struct mhi_link_info link_info;
+	int ret = -EINVAL;
+
+	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state))) {
+		ret =  -EIO;
+		goto exit_bw_scale;
+	}
+
+	if (!MHI_IN_MISSION_MODE(mhi_cntrl->ee))
+		goto exit_bw_scale;
+
+	if (!is_valid_ring_ptr(ev_ring, ptr)) {
+		dev_err(dev,
+			"Event ring rp points outside of the event ring\n");
+		ret =  -EIO;
+		goto exit_bw_scale;
+	}
+
+	dev_rp = mhi_to_virtual(ev_ring, ptr);
+
+	/* If rp points to base, we need to wrap it around */
+	if (dev_rp == ev_ring->base)
+		dev_rp = ev_ring->base + ev_ring->len;
+	dev_rp--;
+
+	/* Fast forward to currently processed element and recycle er */
+	ev_ring->rp = dev_rp;
+	ev_ring->wp = dev_rp - 1;
+	if (ev_ring->wp < ev_ring->base)
+		ev_ring->wp = ev_ring->base + ev_ring->len - ev_ring->el_size;
+	mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
+
+	if (WARN_ON(MHI_TRE_GET_EV_TYPE(dev_rp) != MHI_PKT_TYPE_BW_REQ_EVENT)) {
+		dev_err(dev, "!BW SCALE REQ event\n");
+		goto exit_bw_scale;
+	}
+
+	link_info.target_link_speed = MHI_TRE_GET_EV_LINKSPEED(dev_rp);
+	link_info.target_link_width = MHI_TRE_GET_EV_LINKWIDTH(dev_rp);
+	link_info.sequence_num = MHI_TRE_GET_EV_BW_REQ_SEQ(dev_rp);
+
+	dev_dbg(dev, "Received BW_REQ with seq:%d link speed:0x%x width:0x%x\n",
+		link_info.sequence_num,
+		link_info.target_link_speed,
+		link_info.target_link_width);
+
+	/* Bring host and device out of suspended states */
+	ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
+	if (ret)
+		goto exit_bw_scale;
+
+	mhi_cntrl->runtime_get(mhi_cntrl);
+
+	ret = mhi_cntrl->bw_scale(mhi_cntrl, &link_info);
+	if (!ret)
+		response = 0;
+
+	response = MHI_BW_SCALE_RESULT(response, link_info.sequence_num);
+
+	write_lock_bh(&mhi_cntrl->pm_lock);
+	mhi_write_reg(mhi_cntrl, mhi_cntrl->bw_scale_db, 0, response);
+	write_unlock_bh(&mhi_cntrl->pm_lock);
+
+	mhi_cntrl->runtime_put(mhi_cntrl);
+	mhi_device_put(mhi_cntrl->mhi_dev);
+
+exit_bw_scale:
+	return ret;
+}
+
+void mhi_process_ev_work(struct work_struct *work)
+{
+	struct mhi_event *mhi_event = container_of(work, struct mhi_event,
+						   work);
+
+	struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
+
+	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
+		return;
+
+	guard(mutex)(&mhi_event->mutex);
+	mhi_event->process_event(mhi_cntrl, mhi_event, U32_MAX);
+}
+
 void mhi_ev_task(unsigned long data)
 {
 	struct mhi_event *mhi_event = (struct mhi_event *)data;
diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index 2fb27e6f8f88ebc701dad56dd60844d8470dd418..8b518da4995d83a299f419908b3753e6b78c8803 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -523,7 +523,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
 		if (mhi_event->offload_ev)
 			continue;
 		disable_irq(mhi_cntrl->irq[mhi_event->irq]);
-		tasklet_kill(&mhi_event->task);
+		if (mhi_event->data_type == MHI_ER_BW_SCALE)
+			cancel_work_sync(&mhi_event->work);
+		else
+			tasklet_kill(&mhi_event->task);
 	}
 
 	/* Release lock and wait for all pending threads to complete */
@@ -670,7 +673,10 @@ static void mhi_pm_sys_error_transition(struct mhi_controller *mhi_cntrl)
 	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
 		if (mhi_event->offload_ev)
 			continue;
-		tasklet_kill(&mhi_event->task);
+		if (mhi_event->data_type == MHI_ER_BW_SCALE)
+			cancel_work_sync(&mhi_event->work);
+		else
+			tasklet_kill(&mhi_event->task);
 	}
 
 	/* Release lock and wait for all pending threads to complete */
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index dd372b0123a6da5107b807ff8fe940c567eb2030..2041bbb2e2396eb2e19e6bc0a5e981aa2917ebdd 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -102,10 +102,12 @@ struct image_info {
  * struct mhi_link_info - BW requirement
  * target_link_speed - Link speed as defined by TLS bits in LinkControl reg
  * target_link_width - Link width as defined by NLW bits in LinkStatus reg
+ * sequence_num - used by device to track bw requests sent to host
  */
 struct mhi_link_info {
 	unsigned int target_link_speed;
 	unsigned int target_link_width;
+	int sequence_num;
 };
 
 /**
@@ -183,10 +185,12 @@ enum mhi_ch_ee_mask {
  * enum mhi_er_data_type - Event ring data types
  * @MHI_ER_DATA: Only client data over this ring
  * @MHI_ER_CTRL: MHI control data and client data
+ * @MHI_ER_BW_SCALE: MHI controller bandwidth scale functionality
  */
 enum mhi_er_data_type {
 	MHI_ER_DATA,
 	MHI_ER_CTRL,
+	MHI_ER_BW_SCALE,
 };
 
 /**
@@ -299,6 +303,7 @@ struct mhi_controller_config {
  * @bhi: Points to base of MHI BHI register space
  * @bhie: Points to base of MHI BHIe register space
  * @wake_db: MHI WAKE doorbell register address
+ * @wake_db: MHI BW_SCALE doorbell register address
  * @iova_start: IOMMU starting address for data (required)
  * @iova_stop: IOMMU stop address for data (required)
  * @fw_image: Firmware image name for normal booting (optional)
@@ -355,6 +360,8 @@ struct mhi_controller_config {
  * @write_reg: Write a MHI register via the physical link (required)
  * @reset: Controller specific reset function (optional)
  * @edl_trigger: CB function to trigger EDL mode (optional)
+ * @get_misc_doobell: function to get doorbell used for MISC feature like BW scale etc (optional)
+ * @bw_scale: CB function for passing BW scale info (optional)
  * @buffer_len: Bounce buffer length
  * @index: Index of the MHI controller instance
  * @bounce_buf: Use of bounce buffer
@@ -376,6 +383,7 @@ struct mhi_controller {
 	void __iomem *bhi;
 	void __iomem *bhie;
 	void __iomem *wake_db;
+	void __iomem *bw_scale_db;
 
 	dma_addr_t iova_start;
 	dma_addr_t iova_stop;
@@ -440,6 +448,11 @@ struct mhi_controller {
 	void (*reset)(struct mhi_controller *mhi_cntrl);
 	int (*edl_trigger)(struct mhi_controller *mhi_cntrl);
 
+	int (*get_misc_doorbell)(struct mhi_controller *mhi_cntrl,
+				 enum mhi_er_data_type type);
+	int (*bw_scale)(struct mhi_controller *mhi_cntrl,
+			struct mhi_link_info *link_info);
+
 	size_t buffer_len;
 	int index;
 	bool bounce_buf;

-- 
2.34.1

Re: [PATCH v3 08/11] bus: mhi: host: Add support for Bandwidth scale

[Ilpo Järvinen]

On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:

> As per MHI spec v1.2, sec 14, MHI supports bandwidth scaling to reduce
> power consumption. MHI bandwidth scaling is advertised by devices that
> contain the bandwidth scaling capability registers. If enabled, the device
> aggregates bandwidth requirements and sends them to the host through
> dedicated mhi event ring. After the host performs the bandwidth switch,
> it sends an acknowledgment by ringing a doorbell.
> 
> if the host supports bandwidth scaling events, then it must set
> BW_CFG.ENABLED bit, set BW_CFG.DB_CHAN_ID to the channel ID to the
> doorbell that will be used by the host to communicate the bandwidth
> scaling status and BW_CFG.ER_INDEX to the index for the event ring
> to which the device should send bandwidth scaling request in the
> bandwidth scaling capability register.
> 
> As part of mmio init check if the bw scale capability is present or not,
> if present advertise host supports bw scale by setting all the required
> fields.
> 
> MHI layer will only forward the bw scaling request to the controller
> driver since MHI doesn't have any idea about transport layer used by
> the controller, it is responsibility of the controller driver to do actual
> bw scaling and then pass status to the MHI. MHI will response back to the
> device based up on the status of the bw scale received.
> 
> Add a new get_misc_doorbell() to get doorbell for misc capabilities to
> use the doorbell with mhi events like MHI BW scale etc.
> 
> Use workqueue & mutex for the bw scale events as the pci_set_target_speed()
> which will called by the mhi controller driver can sleep.
> 
> Co-developed-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
> Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/bus/mhi/common.h        | 16 +++++++
>  drivers/bus/mhi/host/init.c     | 61 ++++++++++++++++++++++++-
>  drivers/bus/mhi/host/internal.h |  7 ++-
>  drivers/bus/mhi/host/main.c     | 98 ++++++++++++++++++++++++++++++++++++++++-
>  drivers/bus/mhi/host/pm.c       | 10 ++++-
>  include/linux/mhi.h             | 13 ++++++
>  6 files changed, 199 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> index eedac801b80021e44f7c65d33cd50760e06c02f2..0a02acee709af7a2a6abddcb9547ef56564ce453 100644
> --- a/drivers/bus/mhi/common.h
> +++ b/drivers/bus/mhi/common.h
> @@ -208,6 +208,22 @@
>  #define MHI_RSCTRE_DATA_DWORD1		cpu_to_le32(FIELD_PREP(GENMASK(23, 16), \
>  							       MHI_PKT_TYPE_COALESCING))
>  
> +/* MHI Bandwidth scaling offsets */
> +#define MHI_BW_SCALE_CFG_OFFSET		0x4
> +#define MHI_BW_SCALE_CAP_ID		(3)
> +
> +#define MHI_BW_SCALE_ENABLE(bw_scale_db, er_index)	cpu_to_le32(FIELD_PREP(GENMASK(31, 25), \
> +							bw_scale_db) |				\
> +							FIELD_PREP(GENMASK(23, 19), er_index) |	\
> +							BIT(24))

This code would be easier to understand if you would name those 
GENMASK()s and BIT() with defines first.

Why does this have to be a macro?

These are also hard to read when they're misindented like that.

> +#define MHI_TRE_GET_EV_BW_REQ_SEQ(tre)	FIELD_GET(GENMASK(15, 8), (MHI_TRE_GET_DWORD(tre, 0)))
> +#define MHI_BW_SCALE_DB_ID(er_index)	FIELD_PREP(GENMASK(31, 25), er_index)
> +
> +#define MHI_BW_SCALE_RESULT(status, seq)	cpu_to_le32(FIELD_PREP(GENMASK(11, 8), status) | \
> +						FIELD_PREP(GENMASK(7, 0), seq))
> +#define MHI_BW_SCALE_NACK			0xF
> +
>  enum mhi_pkt_type {
>  	MHI_PKT_TYPE_INVALID = 0x0,
>  	MHI_PKT_TYPE_NOOP_CMD = 0x1,
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index a7137a040bdce1c58c98fe9c2340aae4cc4387d1..9fe6020f7868ec8bd114d0d96edc9d17624cbac5 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -496,10 +496,53 @@ static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability,
>  	return -ENXIO;
>  }
>  
> +static int mhi_get_er_index(struct mhi_controller *mhi_cntrl,
> +			    enum mhi_er_data_type type)
> +{
> +	struct mhi_event *mhi_event = mhi_cntrl->mhi_event;
> +	int i;
> +
> +	/* Find event ring for requested type */
> +	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
> +		if (mhi_event->data_type == type)
> +			return mhi_event->er_index;
> +	}
> +
> +	return -ENOENT;
> +}
> +
> +static int mhi_init_bw_scale(struct mhi_controller *mhi_cntrl,
> +			     int bw_scale_db)
> +{
> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> +	int ret, er_index, val;
> +	u32 bw_cfg_offset;
> +
> +	ret = mhi_find_capability(mhi_cntrl, MHI_BW_SCALE_CAP_ID, &bw_cfg_offset);
> +	if (ret)
> +		return ret;
> +
> +	er_index = mhi_get_er_index(mhi_cntrl, MHI_ER_BW_SCALE);
> +	if (er_index < 0)
> +		return er_index;
> +
> +	bw_cfg_offset += MHI_BW_SCALE_CFG_OFFSET;
> +
> +	/* Advertise host support */
> +	val = MHI_BW_SCALE_ENABLE(bw_scale_db, er_index);
> +
> +	mhi_write_reg(mhi_cntrl, mhi_cntrl->regs, bw_cfg_offset, val);
> +
> +	dev_dbg(dev, "Bandwidth scaling setup complete with event ring: %d\n",
> +		er_index);
> +
> +	return 0;
> +}
> +
>  int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>  {
>  	u32 val;
> -	int i, ret;
> +	int i, ret, doorbell = 0;
>  	struct mhi_chan *mhi_chan;
>  	struct mhi_event *mhi_event;
>  	void __iomem *base = mhi_cntrl->regs;
> @@ -633,6 +676,16 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>  		return ret;
>  	}
>  
> +	if (mhi_cntrl->get_misc_doorbell)
> +		doorbell = mhi_cntrl->get_misc_doorbell(mhi_cntrl, MHI_ER_BW_SCALE);
> +
> +	if (doorbell > 0) {
> +		ret = mhi_init_bw_scale(mhi_cntrl, doorbell);
> +		if (!ret)
> +			mhi_cntrl->bw_scale_db = base + val + (8 * doorbell);
> +		else
> +			dev_warn(dev, "Failed to setup bandwidth scaling: %d\n", ret);
> +	}
>  	return 0;
>  }
>  
> @@ -778,6 +831,9 @@ static int parse_ev_cfg(struct mhi_controller *mhi_cntrl,
>  		case MHI_ER_CTRL:
>  			mhi_event->process_event = mhi_process_ctrl_ev_ring;
>  			break;
> +		case MHI_ER_BW_SCALE:
> +			mhi_event->process_event = mhi_process_bw_scale_ev_ring;
> +			break;
>  		default:
>  			dev_err(dev, "Event Ring type not supported\n");
>  			goto error_ev_cfg;
> @@ -1012,9 +1068,12 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
>  
>  		mhi_event->mhi_cntrl = mhi_cntrl;
>  		spin_lock_init(&mhi_event->lock);
> +		mutex_init(&mhi_event->mutex);
>  		if (mhi_event->data_type == MHI_ER_CTRL)
>  			tasklet_init(&mhi_event->task, mhi_ctrl_ev_task,
>  				     (ulong)mhi_event);
> +		else if (mhi_event->data_type == MHI_ER_BW_SCALE)
> +			INIT_WORK(&mhi_event->work, mhi_process_ev_work);
>  		else
>  			tasklet_init(&mhi_event->task, mhi_ev_task,
>  				     (ulong)mhi_event);
> diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
> index ce566f7d2e9240c64044407aa4124ad3cdb98003..cf64adaecad2aeec8569da5276ec60dd7e97e5e0 100644
> --- a/drivers/bus/mhi/host/internal.h
> +++ b/drivers/bus/mhi/host/internal.h
> @@ -248,6 +248,8 @@ struct mhi_event {
>  	struct mhi_ring ring;
>  	struct db_cfg db_cfg;
>  	struct tasklet_struct task;
> +	struct work_struct work;
> +	struct mutex mutex; /* lock for synchronization */
>  	spinlock_t lock;
>  	int (*process_event)(struct mhi_controller *mhi_cntrl,
>  			     struct mhi_event *mhi_event,
> @@ -410,7 +412,8 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>  				struct mhi_event *mhi_event, u32 event_quota);
>  int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  			     struct mhi_event *mhi_event, u32 event_quota);
> -
> +int mhi_process_bw_scale_ev_ring(struct mhi_controller *mhi_cntrl,
> +				 struct mhi_event *mhi_event, u32 event_quota);
>  /* ISR handlers */
>  irqreturn_t mhi_irq_handler(int irq_number, void *dev);
>  irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *dev);
> @@ -426,5 +429,5 @@ void mhi_unmap_single_no_bb(struct mhi_controller *mhi_cntrl,
>  			    struct mhi_buf_info *buf_info);
>  void mhi_unmap_single_use_bb(struct mhi_controller *mhi_cntrl,
>  			     struct mhi_buf_info *buf_info);
> -
> +void mhi_process_ev_work(struct work_struct *work);
>  #endif /* _MHI_INT_H */
> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> index 9bb0df43ceef1e54e8817422516aab1def6fdc4a..f87e9550b59227947fc7268c5799eea274c66b98 100644
> --- a/drivers/bus/mhi/host/main.c
> +++ b/drivers/bus/mhi/host/main.c
> @@ -472,7 +472,10 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
>  		if (mhi_dev)
>  			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
>  	} else {
> -		tasklet_schedule(&mhi_event->task);
> +		if (mhi_event->data_type == MHI_ER_BW_SCALE)
> +			queue_work(mhi_cntrl->hiprio_wq, &mhi_event->work);
> +		else
> +			tasklet_schedule(&mhi_event->task);
>  	}
>  
>  	return IRQ_HANDLED;
> @@ -1049,6 +1052,99 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>  	return count;
>  }
>  
> +int mhi_process_bw_scale_ev_ring(struct mhi_controller *mhi_cntrl,
> +				 struct mhi_event *mhi_event, u32 event_quota)
> +{
> +	struct mhi_event_ctxt *er_ctxt = &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> +	struct mhi_ring *ev_ring = &mhi_event->ring;
> +	dma_addr_t ptr = le64_to_cpu(er_ctxt->rp);
> +	u32 response = MHI_BW_SCALE_NACK;
> +	struct mhi_ring_element *dev_rp;
> +	struct mhi_link_info link_info;
> +	int ret = -EINVAL;
> +
> +	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state))) {
> +		ret =  -EIO;
> +		goto exit_bw_scale;
> +	}
> +
> +	if (!MHI_IN_MISSION_MODE(mhi_cntrl->ee))
> +		goto exit_bw_scale;
> +
> +	if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +		dev_err(dev,
> +			"Event ring rp points outside of the event ring\n");
> +		ret =  -EIO;
> +		goto exit_bw_scale;
> +	}
> +
> +	dev_rp = mhi_to_virtual(ev_ring, ptr);
> +
> +	/* If rp points to base, we need to wrap it around */
> +	if (dev_rp == ev_ring->base)
> +		dev_rp = ev_ring->base + ev_ring->len;
> +	dev_rp--;
> +
> +	/* Fast forward to currently processed element and recycle er */
> +	ev_ring->rp = dev_rp;
> +	ev_ring->wp = dev_rp - 1;
> +	if (ev_ring->wp < ev_ring->base)
> +		ev_ring->wp = ev_ring->base + ev_ring->len - ev_ring->el_size;
> +	mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
> +
> +	if (WARN_ON(MHI_TRE_GET_EV_TYPE(dev_rp) != MHI_PKT_TYPE_BW_REQ_EVENT)) {
> +		dev_err(dev, "!BW SCALE REQ event\n");
> +		goto exit_bw_scale;
> +	}
> +
> +	link_info.target_link_speed = MHI_TRE_GET_EV_LINKSPEED(dev_rp);
> +	link_info.target_link_width = MHI_TRE_GET_EV_LINKWIDTH(dev_rp);
> +	link_info.sequence_num = MHI_TRE_GET_EV_BW_REQ_SEQ(dev_rp);
> +
> +	dev_dbg(dev, "Received BW_REQ with seq:%d link speed:0x%x width:0x%x\n",
> +		link_info.sequence_num,
> +		link_info.target_link_speed,
> +		link_info.target_link_width);
> +
> +	/* Bring host and device out of suspended states */
> +	ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
> +	if (ret)
> +		goto exit_bw_scale;
> +
> +	mhi_cntrl->runtime_get(mhi_cntrl);
> +
> +	ret = mhi_cntrl->bw_scale(mhi_cntrl, &link_info);
> +	if (!ret)
> +		response = 0;
> +
> +	response = MHI_BW_SCALE_RESULT(response, link_info.sequence_num);
> +
> +	write_lock_bh(&mhi_cntrl->pm_lock);
> +	mhi_write_reg(mhi_cntrl, mhi_cntrl->bw_scale_db, 0, response);
> +	write_unlock_bh(&mhi_cntrl->pm_lock);
> +
> +	mhi_cntrl->runtime_put(mhi_cntrl);
> +	mhi_device_put(mhi_cntrl->mhi_dev);
> +
> +exit_bw_scale:
> +	return ret;
> +}
> +
> +void mhi_process_ev_work(struct work_struct *work)
> +{
> +	struct mhi_event *mhi_event = container_of(work, struct mhi_event,
> +						   work);
> +
> +	struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
> +
> +	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
> +		return;
> +
> +	guard(mutex)(&mhi_event->mutex);
> +	mhi_event->process_event(mhi_cntrl, mhi_event, U32_MAX);
> +}
> +
>  void mhi_ev_task(unsigned long data)
>  {
>  	struct mhi_event *mhi_event = (struct mhi_event *)data;
> diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> index 2fb27e6f8f88ebc701dad56dd60844d8470dd418..8b518da4995d83a299f419908b3753e6b78c8803 100644
> --- a/drivers/bus/mhi/host/pm.c
> +++ b/drivers/bus/mhi/host/pm.c
> @@ -523,7 +523,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
>  		if (mhi_event->offload_ev)
>  			continue;
>  		disable_irq(mhi_cntrl->irq[mhi_event->irq]);
> -		tasklet_kill(&mhi_event->task);
> +		if (mhi_event->data_type == MHI_ER_BW_SCALE)
> +			cancel_work_sync(&mhi_event->work);
> +		else
> +			tasklet_kill(&mhi_event->task);
>  	}
>  
>  	/* Release lock and wait for all pending threads to complete */
> @@ -670,7 +673,10 @@ static void mhi_pm_sys_error_transition(struct mhi_controller *mhi_cntrl)
>  	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
>  		if (mhi_event->offload_ev)
>  			continue;
> -		tasklet_kill(&mhi_event->task);
> +		if (mhi_event->data_type == MHI_ER_BW_SCALE)
> +			cancel_work_sync(&mhi_event->work);
> +		else
> +			tasklet_kill(&mhi_event->task);
>  	}
>  
>  	/* Release lock and wait for all pending threads to complete */
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index dd372b0123a6da5107b807ff8fe940c567eb2030..2041bbb2e2396eb2e19e6bc0a5e981aa2917ebdd 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -102,10 +102,12 @@ struct image_info {
>   * struct mhi_link_info - BW requirement
>   * target_link_speed - Link speed as defined by TLS bits in LinkControl reg
>   * target_link_width - Link width as defined by NLW bits in LinkStatus reg
> + * sequence_num - used by device to track bw requests sent to host
>   */
>  struct mhi_link_info {
>  	unsigned int target_link_speed;
>  	unsigned int target_link_width;
> +	int sequence_num;
>  };
>  
>  /**
> @@ -183,10 +185,12 @@ enum mhi_ch_ee_mask {
>   * enum mhi_er_data_type - Event ring data types
>   * @MHI_ER_DATA: Only client data over this ring
>   * @MHI_ER_CTRL: MHI control data and client data
> + * @MHI_ER_BW_SCALE: MHI controller bandwidth scale functionality
>   */
>  enum mhi_er_data_type {
>  	MHI_ER_DATA,
>  	MHI_ER_CTRL,
> +	MHI_ER_BW_SCALE,
>  };
>  
>  /**
> @@ -299,6 +303,7 @@ struct mhi_controller_config {
>   * @bhi: Points to base of MHI BHI register space
>   * @bhie: Points to base of MHI BHIe register space
>   * @wake_db: MHI WAKE doorbell register address
> + * @wake_db: MHI BW_SCALE doorbell register address
>   * @iova_start: IOMMU starting address for data (required)
>   * @iova_stop: IOMMU stop address for data (required)
>   * @fw_image: Firmware image name for normal booting (optional)
> @@ -355,6 +360,8 @@ struct mhi_controller_config {
>   * @write_reg: Write a MHI register via the physical link (required)
>   * @reset: Controller specific reset function (optional)
>   * @edl_trigger: CB function to trigger EDL mode (optional)
> + * @get_misc_doobell: function to get doorbell used for MISC feature like BW scale etc (optional)
> + * @bw_scale: CB function for passing BW scale info (optional)
>   * @buffer_len: Bounce buffer length
>   * @index: Index of the MHI controller instance
>   * @bounce_buf: Use of bounce buffer
> @@ -376,6 +383,7 @@ struct mhi_controller {
>  	void __iomem *bhi;
>  	void __iomem *bhie;
>  	void __iomem *wake_db;
> +	void __iomem *bw_scale_db;
>  
>  	dma_addr_t iova_start;
>  	dma_addr_t iova_stop;
> @@ -440,6 +448,11 @@ struct mhi_controller {
>  	void (*reset)(struct mhi_controller *mhi_cntrl);
>  	int (*edl_trigger)(struct mhi_controller *mhi_cntrl);
>  
> +	int (*get_misc_doorbell)(struct mhi_controller *mhi_cntrl,
> +				 enum mhi_er_data_type type);
> +	int (*bw_scale)(struct mhi_controller *mhi_cntrl,
> +			struct mhi_link_info *link_info);
> +
>  	size_t buffer_len;
>  	int index;
>  	bool bounce_buf;
> 
> 

-- 
 i.

[PATCH v3 09/11] PCI: Export pci_set_target_speed()

[Krishna Chaitanya Chundru]

Export pci_set_target_speed() so that other kernel drivers can use it
to change the PCIe data rate.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pcie/bwctrl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 3525bc0cd10f1dd7794abbe84ccb10e2c53a10af..02c544c6186b8c6b87730d1c924f07858571d2ae 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -214,6 +214,7 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(pcie_set_target_speed);
 
 static void pcie_bwnotif_enable(struct pcie_device *srv)
 {

-- 
2.34.1

Re: [PATCH v3 09/11] PCI: Export pci_set_target_speed()

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 813 bytes --]

On Mon, 19 May 2025, Krishna Chaitanya Chundru wrote:

> Export pci_set_target_speed() so that other kernel drivers can use it
> to change the PCIe data rate.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/pci/pcie/bwctrl.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
> index 3525bc0cd10f1dd7794abbe84ccb10e2c53a10af..02c544c6186b8c6b87730d1c924f07858571d2ae 100644
> --- a/drivers/pci/pcie/bwctrl.c
> +++ b/drivers/pci/pcie/bwctrl.c
> @@ -214,6 +214,7 @@ int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>  
>  	return ret;
>  }
> +EXPORT_SYMBOL_GPL(pcie_set_target_speed);

Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>


-- 
 i.

[PATCH v3 10/11] PCI: Add function to convert lnkctl2speed to pci_bus_speed

[Krishna Chaitanya Chundru]

Add a exported function to convert lnkctl2speed to enum pci_bus_speed,
so that other kernel drivers can use it.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/pci/pci.c   | 12 ++++++++++++
 include/linux/pci.h |  1 +
 2 files changed, 13 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e77d5b53c0cec9c7cdd043ac44329d1b285cae83..363565fd71bc184bb07e4f21e9009ce382e6075b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6035,6 +6035,18 @@ int pcie_link_speed_mbps(struct pci_dev *pdev)
 }
 EXPORT_SYMBOL(pcie_link_speed_mbps);
 
+/**
+ * pci_lnkctl2_bus_speed - convert lnkctl2 speed to pci_bus_speed
+ * @speed: LNKCAP2 SLS value
+ *
+ * Return: pci_bus_speed
+ */
+enum pci_bus_speed pci_lnkctl2_bus_speed(int speed)
+{
+	return pcie_link_speed[speed];
+}
+EXPORT_SYMBOL(pci_lnkctl2_bus_speed);
+
 /**
  * pcie_bandwidth_available - determine minimum link settings of a PCIe
  *			      device and its bandwidth limitation
diff --git a/include/linux/pci.h b/include/linux/pci.h
index ce9d0812a61c2337ba533ef246393a0101e617ee..48c3f5b1f6f86b652355fc9edbcf834d64fddd11 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1655,6 +1655,7 @@ int pci_cfg_space_size(struct pci_dev *dev);
 unsigned char pci_bus_max_busnr(struct pci_bus *bus);
 resource_size_t pcibios_window_alignment(struct pci_bus *bus,
 					 unsigned long type);
+enum pci_bus_speed pci_lnkctl2_bus_speed(int speed);
 
 #define PCI_VGA_STATE_CHANGE_BRIDGE (1 << 0)
 #define PCI_VGA_STATE_CHANGE_DECODES (1 << 1)

-- 
2.34.1

[PATCH v3 11/11] wifi: ath11k: Add support for MHI bandwidth scaling

[Krishna Chaitanya Chundru]

From: Miaoqing Pan <quic_miaoqing@quicinc.com>

Add support for MHI bandwidth scaling, which will reduce power consumption
if WLAN operates with lower bandwidth. This feature is only enabled for
QCA6390.

Bandwidth scaling is initiated by the endpoint firmware based upon the
bandwidth requirements, if there is high bandwidth data endpoint requests
for higher data rates or if there is less bandwidth they request for lower
data rates to reduce power. Endpoint initiates this through MHI protocol.

Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1

Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath11k/mhi.c | 41 +++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/net/wireless/ath/ath11k/mhi.c b/drivers/net/wireless/ath/ath11k/mhi.c
index fc77eac83e953148b96cad096d26b32222157b24..8057031d654d794f9e882a975f99083c193e492c 100644
--- a/drivers/net/wireless/ath/ath11k/mhi.c
+++ b/drivers/net/wireless/ath/ath11k/mhi.c
@@ -20,6 +20,7 @@
 #define MHI_TIMEOUT_DEFAULT_MS	20000
 #define RDDM_DUMP_SIZE	0x420000
 #define MHI_CB_INVALID	0xff
+#define MHI_BW_SCALE_CHAN_DB 126
 
 static const struct mhi_channel_config ath11k_mhi_channels_qca6390[] = {
 	{
@@ -73,6 +74,17 @@ static struct mhi_event_config ath11k_mhi_events_qca6390[] = {
 		.client_managed = false,
 		.offload_channel = false,
 	},
+	{
+		.num_elements = 8,
+		.irq_moderation_ms = 0,
+		.irq = 1,
+		.mode = MHI_DB_BRST_DISABLE,
+		.data_type = MHI_ER_BW_SCALE,
+		.priority = 2,
+		.hardware_event = false,
+		.client_managed = false,
+		.offload_channel = false,
+	},
 };
 
 static const struct mhi_controller_config ath11k_mhi_config_qca6390 = {
@@ -313,6 +325,33 @@ static void ath11k_mhi_op_write_reg(struct mhi_controller *mhi_cntrl,
 	writel(val, addr);
 }
 
+static int ath11k_mhi_op_get_misc_doorbell(struct mhi_controller *mhi_cntrl,
+					   enum mhi_er_data_type type)
+{
+	if (type == MHI_ER_BW_SCALE)
+		return MHI_BW_SCALE_CHAN_DB;
+
+	return -EINVAL;
+}
+
+static int ath11k_mhi_op_bw_scale(struct mhi_controller *mhi_cntrl,
+				  struct mhi_link_info *link_info)
+{
+	enum pci_bus_speed speed = pci_lnkctl2_bus_speed(link_info->target_link_speed);
+	struct ath11k_base *ab = dev_get_drvdata(mhi_cntrl->cntrl_dev);
+	struct pci_dev *pci_dev = to_pci_dev(ab->dev);
+	struct pci_dev *pdev;
+
+	if (!pci_dev)
+		return -EINVAL;
+
+	pdev = pci_upstream_bridge(pci_dev);
+	if (!pdev)
+		return -ENODEV;
+
+	return pcie_set_target_speed(pdev, speed, true);
+}
+
 static int ath11k_mhi_read_addr_from_dt(struct mhi_controller *mhi_ctrl)
 {
 	struct device_node *np;
@@ -389,6 +428,8 @@ int ath11k_mhi_register(struct ath11k_pci *ab_pci)
 	mhi_ctrl->status_cb = ath11k_mhi_op_status_cb;
 	mhi_ctrl->read_reg = ath11k_mhi_op_read_reg;
 	mhi_ctrl->write_reg = ath11k_mhi_op_write_reg;
+	mhi_ctrl->bw_scale = ath11k_mhi_op_bw_scale;
+	mhi_ctrl->get_misc_doorbell = ath11k_mhi_op_get_misc_doorbell;
 
 	switch (ab->hw_rev) {
 	case ATH11K_HW_QCN9074_HW10:

-- 
2.34.1