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From: Jules Maselbas <jmaselbas@kalray.eu>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH master] usb: dwc2: increase timeout for waiting on host mode
Date: Wed, 21 Apr 2021 11:11:53 +0200
Message-ID: <20210421091153.GE21066@tellis.lin.mbt.kalray.eu> (raw)
In-Reply-To: <27969059-7cfb-cb4a-cd49-52c03c156799@pengutronix.de>

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
> >>
> >>
> > 
> > 
> 
> -- 
> Pengutronix e.K.                           |                             |
> Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
> 31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> 


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  reply	other threads:[~2021-04-21  9:14 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21  7:27 Ahmad Fatoum
2021-04-21  8:47 ` Jules Maselbas
2021-04-21  8:50   ` Ahmad Fatoum
2021-04-21  9:11     ` Jules Maselbas [this message]
2021-05-07  8:07     ` Sascha Hauer
2021-06-02 11:21       ` Ahmad Fatoum

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