Re: [RESEND][PATCH] Bluetooth: Make request workqueue freezable
From: Arend van Spriel
Date: Fri May 22 2015 - 03:37:26 EST
On 05/22/15 02:21, Laura Abbott wrote:
On 05/21/2015 08:26 AM, Alan Stern wrote:
On Thu, 21 May 2015, Marcel Holtmann wrote:
Hi Alan,
Then avoiding the failed firmware is no solution, indeed.
If it's a new probe, it should be never executed during resume.
Can you expand this comment? What's wrong with probing during resume?
The USB stack does carry out probes during resume under certain
circumstances. A driver lacking a reset_resume callback is one of
those circumstances.
in case the platform kills the power to the USB lines, we can never
do anything about this. I do not want to hack around this in the
driver.
What are the cases where we should implement reset_resume and would
it really help here. Since the btusb.ko driver implements
suspend/resume support, would reset_resume ever be called?
One of those cases is exactly what you have been talking about: when
the platform kills power to the USB lines during suspend. The driver's
reset_resume routine will be called during resume, as opposed to the
probe routine being called. Therefore the driver will be able to tell
that this is not a new device instance.
The other cases are less likely to occur: a device is unable to resume
normally and requires a reset before it will start working again, or
something else goes wrong along those lines.
However I get the feeling someone needs to go back and see if the
device is the same one and just gets probed again or if it is a new
one from the USB host stack perspective.
That can be done easily enough by enabling usbcore debugging before
carrying out the system suspend:
echo 'module usbcore =p' >/debug/dynamic_debug/control
The debugging information in the kernel log will tell just what
happened.
Playing around in my test setup as a baseline
[ 41.991035] usb usb1-port11: not reset yet, waiting 50ms
[ 42.092902] usb 1-11: reset full-speed USB device number 4 using xhci_hcd
[ 42.143575] usb usb1-port11: not reset yet, waiting 50ms
[ 42.257822] btusb 1-11:1.0: no reset_resume for driver btusb?
[ 42.257823] btusb 1-11:1.1: no reset_resume for driver btusb?
[ 42.257825] btusb 1-11:1.0: forced unbind
[ 42.258305] kworker/dying (826) used greatest stack depth: 10680 bytes
left
[ 42.331342] usb 1-9.2: reset full-speed USB device number 7 using xhci_hcd
[ 42.416631] usb 1-9.2: ep0 maxpacket = 8
[ 42.681288] usb 1-9.1: reset low-speed USB device number 5 using xhci_hcd
[ 42.968138] usb 1-9.1: ep 0x81 - rounding interval to 64 microframes,
ep desc says 80 microframes
[ 42.968157] usb 1-9.1: ep 0x82 - rounding interval to 64 microframes,
ep desc says 80 microframes
[ 43.036290] usb 1-9.4: reset high-speed USB device number 8 using xhci_hcd
[ 43.123126] hub 1-9.4:1.0: hub_reset_resume
[ 43.123581] hub 1-9.4:1.0: enabling power on all ports
[ 43.224853] PM: resume of devices complete after 2456.587 msecs
[ 43.225038] btusb 1-11:1.0: usb_probe_interface
[ 43.225040] btusb 1-11:1.0: usb_probe_interface - got id
[ 43.225802] ------------[ cut here ]------------
[ 43.225807] WARNING: CPU: 7 PID: 2844 at
drivers/base/firmware_class.c:1118 _request_firmware+0x5ee/0x890()
so it is trying to call the reset resume. If I try a 'dummy reset resume'
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index a7bdac0..cda8137 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -3401,6 +3401,7 @@ static struct usb_driver btusb_driver = {
#ifdef CONFIG_PM
.suspend = btusb_suspend,
.resume = btusb_resume,
+ .reset_resume = btusb_resume,
#endif
.id_table = btusb_table,
.supports_autosuspend = 1,
I no longer see the warning which means that probe is no longer being
called.
Marcel, does implementing a proper reset_resume callback seem like the
right
approach or do you need more information?
Hi, Laura
I believe that some devices supported by btusb would need to do a
request_firmware() in the reset_resume() callback and thus end up with
the same issue. btusb could store the firmware obtained during the probe
in it driver private structure and use that in reset_resume() callback,
but it means the memory for the firmware blobs will not be released
until the driver is unloaded.
Regards,
Arend
Thanks,
Laura
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