Re: [PATCH master] usb: dwc2: increase timeout for waiting on host mode

[Jules Maselbas <jmaselbas@kalray.eu>]

On Wed, Apr 21, 2021 at 10:50:52AM +0200, Ahmad Fatoum wrote:
> Hello Jules,
> 
> On 21.04.21 10:47, Jules Maselbas wrote:
> > Hi Ahmad,
> > 
> > On Wed, Apr 21, 2021 at 09:27:04AM +0200, Ahmad Fatoum wrote:
> >> Commit 26459ab7803a ("usb: dwc2: Rework wait for host mode during
> >> core reset") effectively reduced the timeout on switch to host mode
> >> from 200ms to 110 us, which is insufficient for the IP on the Raspberry
> >> Pi 3b, leading to:
> >>
> >>   dwc2 3f980000.usb@7e980000.of: dwc2_wait_for_mode: Couldn't set host mode
> >>
> >> and an unusable USB (and Ethernet) after.
> >>
> >> Bump up the timeout to 200ms and help future debugging by logging how
> >> much time it actually took. For the Raspberry 3b I got a value of 49ms.
> > Indeed, I've changed the timeout in Commit 26459ab7803a, I've tried to
> > follow what's done in Linux in drivers/usb/dwc2/core.c, see
> > https://elixir.bootlin.com/linux/latest/source/drivers/usb/dwc2/core.c#L385
> > 
> > Turns out I've made a mistake, Linux is using 110 ms and not µs.
> > So maybe we can use 110 * MSECOND ? it will still be greater than what's
> > required for the Raspberry 3b.  In the other hand the wait will stop as
> > soon as the mode is set. it will only make the worst case faster...
> > which is not a big deal.
> 
> I am fine with aligning ourselves with what Linux is doing.
> Can you post that as a separate patch? That way this here can go into
> v2021.05.0 to fix the immediate breakage and yours can go into v2020.06.0,
> which will hopefully afford users some more time to test.
Yes, sure I'll send a patch for this, and maybe with some more for dwc2. 

> 
> Cheers,
> Ahmad
> 
> >>
> >> Note that this is also called from dwc2_force_mode, so worst case is
> >> that a stuck IP delays barebox startup by 200ms.
> >> An error message would alert to this fact, so it can be corrected.
> > Ok, this can be useful.
> > 
> >> Fixes: 26459ab7803a ("usb: dwc2: Rework wait for host mode during core reset")
> >> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> >> ---
> >>  drivers/usb/dwc2/core.c | 20 ++++++++++++--------
> >>  1 file changed, 12 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c
> >> index 5d04a07b0393..7813344ffa65 100644
> >> --- a/drivers/usb/dwc2/core.c
> >> +++ b/drivers/usb/dwc2/core.c
> >> @@ -688,19 +688,23 @@ int dwc2_get_dr_mode(struct dwc2 *dwc2)
> >>   */
> >>  void dwc2_wait_for_mode(struct dwc2 *dwc2, bool host_mode)
> >>  {
> >> -	unsigned int timeout = 110 * USECOND;
> >> -	int ret;
> >> +	unsigned int timeout = 200 * MSECOND;
> >> +	uint64_t start;
> >>  
> >>  	dev_vdbg(dwc2->dev, "Waiting for %s mode\n",
> >>  		 host_mode ? "host" : "device");
> >>  
> >> -	ret = wait_on_timeout(timeout, dwc2_is_host_mode(dwc2) == host_mode);
> >> -	if (ret)
> >> -		dev_err(dwc2->dev, "%s: Couldn't set %s mode\n",
> >> -				 __func__, host_mode ? "host" : "device");
> >> +	start = get_time_ns();
> >> +	while (dwc2_is_host_mode(dwc2) != host_mode) {
> >> +		if (is_timeout(start, timeout)) {
> >> +			dev_err(dwc2->dev, "%s: Couldn't set %s mode\n",
> >> +				__func__, host_mode ? "host" : "device");
> >> +			return;
> >> +		}
> >> +	}
> >>  
> >> -	dev_vdbg(dwc2->dev, "%s mode set\n",
> >> -		 host_mode ? "Host" : "Device");
> >> +	dev_vdbg(dwc2->dev, "%s mode set after %lluns\n",
> >> +		 host_mode ? "Host" : "Device", get_time_ns() - start);
> >>  }
> >>  
> >>  /**
> >> -- 
> >> 2.29.2
> >>
> >>
> > 
> > 
> 
> -- 
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> 


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