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SubjectRe: [PATCH] HID: usbhid: do not sleep when opening device
On Fri, May 29, 2020 at 12:59:51PM -0700, Dmitry Torokhov wrote:
> usbhid tries to give the device 50 milliseconds to drain its queues
> when opening the device, but does it naively by simply sleeping in open
> handler, which slows down device probing (and thus may affect overall
> boot time).
>
> However we do not need to sleep as we can instead mark a point of time
> in the future when we should start processing the events.
>
> Reported-by: Nicolas Boichat <drinkcat@chromium.org>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
> drivers/hid/usbhid/hid-core.c | 27 +++++++++++++++------------
> drivers/hid/usbhid/usbhid.h | 1 +
> 2 files changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
> index c7bc9db5b192..e69992e945b2 100644
> --- a/drivers/hid/usbhid/hid-core.c
> +++ b/drivers/hid/usbhid/hid-core.c
> @@ -95,6 +95,19 @@ static int hid_start_in(struct hid_device *hid)
> set_bit(HID_NO_BANDWIDTH, &usbhid->iofl);
> } else {
> clear_bit(HID_NO_BANDWIDTH, &usbhid->iofl);
> +
> + if (test_and_clear_bit(HID_RESUME_RUNNING,
> + &usbhid->iofl)) {
> + /*
> + * In case events are generated while nobody was
> + * listening, some are released when the device
> + * is re-opened. Wait 50 msec for the queue to
> + * empty before allowing events to go through
> + * hid.
> + */
> + usbhid->input_start_time = jiffies +
> + msecs_to_jiffies(50);
> + }
> }
> }
> spin_unlock_irqrestore(&usbhid->lock, flags);
> @@ -280,7 +293,8 @@ static void hid_irq_in(struct urb *urb)
> if (!test_bit(HID_OPENED, &usbhid->iofl))
> break;
> usbhid_mark_busy(usbhid);
> - if (!test_bit(HID_RESUME_RUNNING, &usbhid->iofl)) {
> + if (!test_bit(HID_RESUME_RUNNING, &usbhid->iofl) &&
> + time_after(jiffies, usbhid->input_start_time)) {
> hid_input_report(urb->context, HID_INPUT_REPORT,
> urb->transfer_buffer,
> urb->actual_length, 1);
> @@ -714,17 +728,6 @@ static int usbhid_open(struct hid_device *hid)
> }
>
> usb_autopm_put_interface(usbhid->intf);
> -
> - /*
> - * In case events are generated while nobody was listening,
> - * some are released when the device is re-opened.
> - * Wait 50 msec for the queue to empty before allowing events
> - * to go through hid.
> - */
> - if (res == 0)
> - msleep(50);
> -
Can you just set usbhid->input_start_time here ?
if (res == 0)
usbhid->input_start_time = jiffies + msecs_to_jiffies(50);
clear_bit(HID_RESUME_RUNNING, &usbhid->iofl);

Then you might not need the added code in hid_start_in().

Thanks,
Guenter

> - clear_bit(HID_RESUME_RUNNING, &usbhid->iofl);
> return res;
> }
>
> diff --git a/drivers/hid/usbhid/usbhid.h b/drivers/hid/usbhid/usbhid.h
> index 8620408bd7af..805949671b96 100644
> --- a/drivers/hid/usbhid/usbhid.h
> +++ b/drivers/hid/usbhid/usbhid.h
> @@ -82,6 +82,7 @@ struct usbhid_device {
>
> spinlock_t lock; /* fifo spinlock */
> unsigned long iofl; /* I/O flags (CTRL_RUNNING, OUT_RUNNING) */
> + unsigned long input_start_time; /* When to start handling input, in jiffies */
> struct timer_list io_retry; /* Retry timer */
> unsigned long stop_retry; /* Time to give up, in jiffies */
> unsigned int retry_delay; /* Delay length in ms */
> --
> 2.27.0.rc0.183.gde8f92d652-goog
>
>
> --
> Dmitry

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