[linux-uvc-devel] Cannot shutdown power use from built in webcam in thinkpad T530 questions]

[Marc MERLIN]

Howdy,

I have a T530 with a built in webcam that uses the uvcvideo driver.
Kernel 3.10.6, but the problem has been there for many kernel versions.

[Marc MERLIN]

gandalfthegreat:/sys/bus/usb/devices/3-1.6/power# grep . *
active_duration:61227648
async:enabled
autosuspend:2
autosuspend_delay_ms:2000
connected_duration:66830880
control:auto
level:auto
persist:1
runtime_active_kids:0
runtime_active_time:18870052
runtime_enabled:enabled
runtime_status:active
runtime_suspended_time:5324088
runtime_usage:0

This all looks correct.

Since then, I've confirmed that I don't have the problem some time after
reboot. It may be that the device doesn't seem to sleep well after I've used
it once.

What's interesting, is that I see this when power is plugged in:

Power est. Events/s Category Description
8.18 W 100.0% Device USB device: Yubico Yubikey II (Yubico)
8.13 W 100.0% Device USB device: Integrated Camera (Chicony Electronics Co., Ltd.)

Somehow I know that my Yubikey isn't using 8W, so powertop numbers need to
be taken with a grain of salt.


Once I go to batteries, I see this:
Summary: 760.1 wakeups/second, 718.9 GPU ops/seconds, 0.0 VFS ops/sec and 6.9% CPU use

Power est. Usage Events/s Category Description
8.32 W 100.0% Device USB device: Yubico Yubikey II (Yubico)
2.52 W 73.3% Device Display backlight

So at least for now, the camera does sleep ok, until later when it probably won't again.

I'm somehow thinking there is a driver or hardware problem when the device
does get stuck in a mode where it won't sleep properly again until the next
reboot (just unloading/loading the driver does not fix this).

Any ideas?

You might get more information from a kernel with CONFIG_USB_DEBUG
enabled. Especially if you add
#define VERBOSE_DEBUG
to drivers/usb/core/driver.c before the first #include line.

Do you think thaty would help debug the problem above, or not really? I'm
starting to think that the USB layer is not at fault, although I could be
wrong I suppose.

Thanks,
Marc