Re: [PATCH v2] USB: HID: random timeout failures tackle try.

[Johan Hovold <johan@kernel.org>]

On Tue, Feb 04, 2020 at 01:06:59PM +0200, Lauri Jakku wrote:
> There is multiple reports of random behaviour of USB HID devices.
> 
> I have mouse that acts sometimes quite randomly, I debugged with
> logs others have published: that there is HW timeouts that leave
> device in state that it is errorneus.
> 
> To fix this, I introduce retry mechanism in root of USB HID drivers.
> 
> Fix does not slow down operations at all if there is no -ETIMEDOUT
> got from control message sending. 
> 
> If there is one, then sleep 20ms and try again. Retry count is 20
> witch translates maximium of 400ms before giving up. If the 400ms
> boundary is reached the HW is really bad.

That's not even true. The caller passes in a timeout, in many cases 5
seconds, which you allow to expire up to 20 times on top of your
arbitrary 400 ms delay. So that's 100.4 seconds...

> JUST to be clear:
>     This does not make USB HID devices to sleep anymore than
>     before, if all is golden.
> 
> Why modify usb-hid-core: No need to modify driver by driver.

Because you cannot decide how every use should handle timeouts.

Just fix up the driver that needs this.

> Signed-off-by: Lauri Jakku <lja@iki.fi>
> ---
>  drivers/usb/core/message.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
> index 5adf489428aa..b375e376ea22 100644
> --- a/drivers/usb/core/message.c
> +++ b/drivers/usb/core/message.c
> @@ -20,6 +20,7 @@
>  #include <linux/usb/hcd.h>	/* for usbcore internals */
>  #include <linux/usb/of.h>
>  #include <asm/byteorder.h>
> +#include <linux/errno.h>
>  
>  #include "usb.h"
>  
> @@ -137,7 +138,10 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
>  		    __u16 size, int timeout)
>  {
>  	struct usb_ctrlrequest *dr;
> -	int ret;
> +	int ret = -ETIMEDOUT;
> +
> +	/* retry_cnt * 20ms, max retry time set to 400ms */
> +	int retry_cnt = 20;
>  
>  	dr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_NOIO);
>  	if (!dr)
> @@ -149,11 +153,27 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
>  	dr->wIndex = cpu_to_le16(index);
>  	dr->wLength = cpu_to_le16(size);
>  
> -	ret = usb_internal_control_msg(dev, pipe, dr, data, size, timeout);
> +	do {
> +		ret = usb_internal_control_msg(dev,
> +					pipe,
> +					dr,
> +					data,
> +					size,
> +					timeout);
> +
> +		/*
> +		 * Linger a bit, prior to the next control message
> +		 * or if return value is timeout, but do try few
> +		 * times (max 400ms) before quitting.
> +		 */
> +		if (dev->quirks & USB_QUIRK_DELAY_CTRL_MSG)
> +			msleep(200);
> +		else if (ret == -ETIMEDOUT)
> +			msleep(20);
> +
> +		/* Loop while timeout, max loops: retry_cnt times. */
> +	} while ((retry_cnt-- > 0) && (ret == -ETIMEDOUT));
>  
> -	/* Linger a bit, prior to the next control message. */
> -	if (dev->quirks & USB_QUIRK_DELAY_CTRL_MSG)
> -		msleep(200);
>  
>  	kfree(dr);

Johan