[PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[Lu Baolu]

Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
root hub. The intention of that change was to avoid touching usb core
internal field, a.k.a. lpm_capable, and let usb core to set it by
checking U1 and U2 exit latency values in the descriptor.

Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
root hub is a special usb device as it has no parent. Hub_port_init()
will never be called for a root hub device. That means lpm_capable will
by no means be set for the root hub. As the result, lpm isn't functional
at all in Linux kernel.

This patch add the code to check and set lpm_capable when registering a
root hub device. It could be back-ported to kernels as old as v3.15,
that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
a host supports Link PM.").

Cc: stable@vger.kernel.org # 3.15
Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/usb/core/hcd.c | 6 ++++++
 drivers/usb/core/hub.c | 2 +-
 drivers/usb/core/usb.h | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 45a915c..48b208d 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
 		}
 	}
 
+	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
+		retval = usb_get_bos_descriptor(usb_dev);
+		if (!retval)
+			usb_dev->lpm_capable = usb_device_supports_lpm(usb_dev);
+	}
+
 	retval = usb_new_device (usb_dev);
 	if (retval) {
 		dev_err (parent_dev, "can't register root hub for %s, %d\n",
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3b71516..884d702 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -122,7 +122,7 @@ struct usb_hub *usb_hub_to_struct_hub(struct usb_device *hdev)
 	return usb_get_intfdata(hdev->actconfig->interface[0]);
 }
 
-static int usb_device_supports_lpm(struct usb_device *udev)
+int usb_device_supports_lpm(struct usb_device *udev)
 {
 	/* USB 2.1 (and greater) devices indicate LPM support through
 	 * their USB 2.0 Extended Capabilities BOS descriptor.
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 7eb1e26..d5668c4 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -82,6 +82,7 @@ extern int usb_runtime_suspend(struct device *dev);
 extern int usb_runtime_resume(struct device *dev);
 extern int usb_runtime_idle(struct device *dev);
 extern int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable);
+extern int usb_device_supports_lpm(struct usb_device *udev);
 
 #else
 
-- 
2.1.4

Re: [PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[Greg Kroah-Hartman]

On Fri, Jun 12, 2015 at 09:29:37AM +0800, Lu Baolu wrote:
> Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
> Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
> root hub. The intention of that change was to avoid touching usb core
> internal field, a.k.a. lpm_capable, and let usb core to set it by
> checking U1 and U2 exit latency values in the descriptor.
> 
> Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
> root hub is a special usb device as it has no parent. Hub_port_init()
> will never be called for a root hub device. That means lpm_capable will
> by no means be set for the root hub. As the result, lpm isn't functional
> at all in Linux kernel.
> 
> This patch add the code to check and set lpm_capable when registering a
> root hub device. It could be back-ported to kernels as old as v3.15,
> that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
> a host supports Link PM.").
> 
> Cc: stable@vger.kernel.org # 3.15
> Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/usb/core/hcd.c | 6 ++++++
>  drivers/usb/core/hub.c | 2 +-
>  drivers/usb/core/usb.h | 1 +
>  3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 45a915c..48b208d 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
>  		}
>  	}
>  
> +	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {

Why are you treating a binary coded value as a hex number to compare
against?

Re: [PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[Lu, Baolu]

On 06/12/2015 12:32 PM, Greg Kroah-Hartman wrote:
> On Fri, Jun 12, 2015 at 09:29:37AM +0800, Lu Baolu wrote:
>> Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
>> Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
>> root hub. The intention of that change was to avoid touching usb core
>> internal field, a.k.a. lpm_capable, and let usb core to set it by
>> checking U1 and U2 exit latency values in the descriptor.
>>
>> Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
>> root hub is a special usb device as it has no parent. Hub_port_init()
>> will never be called for a root hub device. That means lpm_capable will
>> by no means be set for the root hub. As the result, lpm isn't functional
>> at all in Linux kernel.
>>
>> This patch add the code to check and set lpm_capable when registering a
>> root hub device. It could be back-ported to kernels as old as v3.15,
>> that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
>> a host supports Link PM.").
>>
>> Cc: stable@vger.kernel.org # 3.15
>> Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>>   drivers/usb/core/hcd.c | 6 ++++++
>>   drivers/usb/core/hub.c | 2 +-
>>   drivers/usb/core/usb.h | 1 +
>>   3 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 45a915c..48b208d 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
>> @@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
>>   		}
>>   	}
>>   
>> +	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
> Why are you treating a binary coded value as a hex number to compare
> against?

The value of the bcdUSB field is 0xJJMN for version JJ.M.N, where
JJ – major version number,
M – minor version number,
N – sub-minor version number

I saw several places in usb core where it is treated as a hex and
check the version requirement like this. Do you want me to
separate it into three numbers and check major/minor/sub-minor
versions separately?

Thanks,
Baolu
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-usb" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>

Re: [PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[Alan Stern]

On Fri, 12 Jun 2015, Lu Baolu wrote:

> Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
> Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
> root hub. The intention of that change was to avoid touching usb core
> internal field, a.k.a. lpm_capable, and let usb core to set it by
> checking U1 and U2 exit latency values in the descriptor.
> 
> Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
> root hub is a special usb device as it has no parent. Hub_port_init()
> will never be called for a root hub device. That means lpm_capable will
> by no means be set for the root hub. As the result, lpm isn't functional
> at all in Linux kernel.
> 
> This patch add the code to check and set lpm_capable when registering a
> root hub device. It could be back-ported to kernels as old as v3.15,
> that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
> a host supports Link PM.").
> 
> Cc: stable@vger.kernel.org # 3.15
> Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/usb/core/hcd.c | 6 ++++++
>  drivers/usb/core/hub.c | 2 +-
>  drivers/usb/core/usb.h | 1 +
>  3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 45a915c..48b208d 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
>  		}
>  	}
>  
> +	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
> +		retval = usb_get_bos_descriptor(usb_dev);
> +		if (!retval)
> +			usb_dev->lpm_capable = usb_device_supports_lpm(usb_dev);
> +	}
> +

This should be integrated with the code immediately above it, which 
also calls usb_get_bos_descriptor().  In fact, maybe you should simply 
change the existing code to check bcdUSB >= 0x0201 instead of speed == 
USB_SPEED_SUPER.

>  	retval = usb_new_device (usb_dev);
>  	if (retval) {
>  		dev_err (parent_dev, "can't register root hub for %s, %d\n",
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 3b71516..884d702 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -122,7 +122,7 @@ struct usb_hub *usb_hub_to_struct_hub(struct usb_device *hdev)
>  	return usb_get_intfdata(hdev->actconfig->interface[0]);
>  }
>  
> -static int usb_device_supports_lpm(struct usb_device *udev)
> +int usb_device_supports_lpm(struct usb_device *udev)
>  {
>  	/* USB 2.1 (and greater) devices indicate LPM support through
>  	 * their USB 2.0 Extended Capabilities BOS descriptor.
> diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
> index 7eb1e26..d5668c4 100644
> --- a/drivers/usb/core/usb.h
> +++ b/drivers/usb/core/usb.h
> @@ -82,6 +82,7 @@ extern int usb_runtime_suspend(struct device *dev);
>  extern int usb_runtime_resume(struct device *dev);
>  extern int usb_runtime_idle(struct device *dev);
>  extern int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable);
> +extern int usb_device_supports_lpm(struct usb_device *udev);
>  
>  #else

This will break if you build it with CONFIG_PM disabled.

Alan Stern

Re: [PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device

[Lu, Baolu]

On 06/13/2015 01:43 AM, Alan Stern wrote:
> On Fri, 12 Jun 2015, Lu Baolu wrote:
>
>> Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
>> Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
>> root hub. The intention of that change was to avoid touching usb core
>> internal field, a.k.a. lpm_capable, and let usb core to set it by
>> checking U1 and U2 exit latency values in the descriptor.
>>
>> Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
>> root hub is a special usb device as it has no parent. Hub_port_init()
>> will never be called for a root hub device. That means lpm_capable will
>> by no means be set for the root hub. As the result, lpm isn't functional
>> at all in Linux kernel.
>>
>> This patch add the code to check and set lpm_capable when registering a
>> root hub device. It could be back-ported to kernels as old as v3.15,
>> that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
>> a host supports Link PM.").
>>
>> Cc: stable@vger.kernel.org # 3.15
>> Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>>   drivers/usb/core/hcd.c | 6 ++++++
>>   drivers/usb/core/hub.c | 2 +-
>>   drivers/usb/core/usb.h | 1 +
>>   3 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 45a915c..48b208d 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
>> @@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
>>   		}
>>   	}
>>   
>> +	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
>> +		retval = usb_get_bos_descriptor(usb_dev);
>> +		if (!retval)
>> +			usb_dev->lpm_capable = usb_device_supports_lpm(usb_dev);
>> +	}
>> +
> This should be integrated with the code immediately above it, which
> also calls usb_get_bos_descriptor().  In fact, maybe you should simply
> change the existing code to check bcdUSB >= 0x0201 instead of speed ==
> USB_SPEED_SUPER.

I agree with you and will change it in v2 patch.

>
>>   	retval = usb_new_device (usb_dev);
>>   	if (retval) {
>>   		dev_err (parent_dev, "can't register root hub for %s, %d\n",
>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
>> index 3b71516..884d702 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -122,7 +122,7 @@ struct usb_hub *usb_hub_to_struct_hub(struct usb_device *hdev)
>>   	return usb_get_intfdata(hdev->actconfig->interface[0]);
>>   }
>>   
>> -static int usb_device_supports_lpm(struct usb_device *udev)
>> +int usb_device_supports_lpm(struct usb_device *udev)
>>   {
>>   	/* USB 2.1 (and greater) devices indicate LPM support through
>>   	 * their USB 2.0 Extended Capabilities BOS descriptor.
>> diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
>> index 7eb1e26..d5668c4 100644
>> --- a/drivers/usb/core/usb.h
>> +++ b/drivers/usb/core/usb.h
>> @@ -82,6 +82,7 @@ extern int usb_runtime_suspend(struct device *dev);
>>   extern int usb_runtime_resume(struct device *dev);
>>   extern int usb_runtime_idle(struct device *dev);
>>   extern int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable);
>> +extern int usb_device_supports_lpm(struct usb_device *udev);
>>   
>>   #else
> This will break if you build it with CONFIG_PM disabled.

Yes. Will fix it in v2 patch.

>
> Alan Stern

Thank you,
Baolu

>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>
>