On 06/13/2015 11:00 PM, Alan Stern wrote:
On Sat, 13 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@xxxxxxxxxxxxxxx # 3.15
Reported-by: Kevin Strasser <kevin.strasser@xxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
--- 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
@@ -106,6 +107,11 @@ static inline int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable)
return 0;
}
+static inline int usb_device_supports_lpm(struct usb_device *udev)
+{
+ return 0;
+}
+
#endif
extern struct bus_type usb_bus_type;
In fact, usb_device_supports_lpm() is compiled even when CONFIG_PM
isn't set. Maybe this should be changed. But if you don't want to
change it now, you need to put the declaration outside the "#ifdef
CONFIG_PM" region. As it is, your patch is still broken (did you try
building it with CONFIG_PM unset?).
I am sorry for this silly mistake. I will move it out of CONFIG_PM region.
I tried building with CONFIG_PM unset. But it turns out that CONFIG_PM
was auto selected by some other items. I will test my next version of
patch with CONFIG_PM *really* unset before sending it out.
Thanks,
Baolu
Alan Stern
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