Re: [PATCH] xhci: Check all endpoints for LPM timeout

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 12.9.2019 17.49, Jan Schmidt wrote:
> If an endpoint is encountered that returns USB3_LPM_DEVICE_INITIATED, keep
> checking further endpoints, as there might be periodic endpoints later
> that return USB3_LPM_DISABLED due to shorter service intervals.
> 
> Without this, the code can set too high a maximum-exit-latency and
> prevent the use of multiple USB3 cameras that should be able to work.
> 
> Signed-off-by: Jan Schmidt <jan@centricular.com>
> Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
> ---
>   drivers/usb/host/xhci.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 03d1e552769b..1986b88661fc 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4673,12 +4673,12 @@ static int xhci_update_timeout_for_endpoint(struct xhci_hcd *xhci,
>   	alt_timeout = xhci_call_host_update_timeout_for_endpoint(xhci, udev,
>   		desc, state, timeout);
>   
> -	/* If we found we can't enable hub-initiated LPM, or
> +	/* If we found we can't enable hub-initiated LPM, and
>   	 * the U1 or U2 exit latency was too high to allow
> -	 * device-initiated LPM as well, just stop searching.
> +	 * device-initiated LPM as well, then we will disable LPM
> +	 * for this device, so stop searching any further.
>   	 */
> -	if (alt_timeout == USB3_LPM_DISABLED ||
> -			alt_timeout == USB3_LPM_DEVICE_INITIATED) {
> +	if (alt_timeout == USB3_LPM_DISABLED) {
>   		*timeout = alt_timeout;
>   		return -E2BIG;
>   	}
> 

Thanks, nice catch. Adding to queue.

While looking at this I see we have a similar issue if driver has
"disable_hub_initiated_lpm" flag set.

xhci_get_timeout_no_hub_lpm() might return USB3_LPM_DEVICE_INITIATED
before we check if periodic endpoints would require disabling LPM
completely.

xhci_calculate_lpm_timeout()
...
     for (i = 0; i < config->desc.bNumInterfaces; i++) {
         ...
         if (intf->dev.driver) {
             ...
             if (driver && driver->disable_hub_initiated_lpm) {
                 return xhci_get_timeout_no_hub_lpm(udev, state);

I'll write a patch for that

-Mathias