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

From: Jan Schmidt <jan@centricular.com>
To: Mathias Nyman <mathias.nyman@linux.intel.com>, linux-usb@vger.kernel.org
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Subject: Re: [PATCH] xhci: Check all endpoints for LPM timeout
Date: Fri, 13 Sep 2019 23:46:39 +1000	[thread overview]
Message-ID: <7e3aca8f-3918-08be-f1fd-cb3299c2af16@centricular.com> (raw)
In-Reply-To: <896688f6-8486-3826-ee74-a225936f824d@linux.intel.com>

On 13/9/19 10:58 pm, Mathias Nyman wrote:
> 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.

Great news for the Oculus Rift support we're working on :)

> 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.

Indeed - sorry, I didn't even think to look past the immediate issue.

> 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

I'll be happy to test by hard-coding the flag.

- Jan.

> 
> -Mathias

-- 
Jan Schmidt, Centricular Ltd - https://centricular.com/