linux-kernel - Re: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by device controller

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Date:   Fri, 08 May 2020 15:35:23 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Jun Li <lijun.kernel@...il.com>,
        John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Yu Chen <chenyu56@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        ShuFan Lee <shufan_lee@...htek.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Jack Pham <jackp@...eaurora.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "open list\:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by device controller


Hi,

Jun Li <lijun.kernel@...il.com> writes:
> Jun Li <lijun.kernel@...il.com> 于2020年5月7日周四 上午11:08写道：
>>
>> John Stultz <john.stultz@...aro.org> 于2020年5月7日周四 上午6:27写道：
>> >
>> > On Wed, May 6, 2020 at 2:00 AM Jun Li <lijun.kernel@...il.com> wrote:
>> > > John Stultz <john.stultz@...aro.org> 于2019年10月30日周三 上午5:18写道：
>> > > > On Tue, Oct 29, 2019 at 2:11 AM Felipe Balbi <balbi@...nel.org> wrote:
>> > > > > John Stultz <john.stultz@...aro.org> writes:
>> > > > > > From: Yu Chen <chenyu56@...wei.com>
>> > > > > >
>> > > > > > It needs more time for the device controller to clear the CmdAct of
>> > > > > > DEPCMD on Hisilicon Kirin Soc.
>> > > > >
>> > > > > Why does it need more time? Why is it so that no other platform needs
>> > > > > more time, only this one? And which command, specifically, causes
>> > > > > problem?
>> > >
>> > > Sorry for my back to this so late.
>> > >
>> > > This change is required on my dwc3 based HW too, I gave a check
>> > > and the reason is suspend_clk is used in case the PIPE phy is at P3,
>> > > this slow clock makes my EP command below timeout.
>> > >
>> > > dwc3_gadget_ep_cmd: ep0out: cmd 'Set Endpoint Configuration' [401]
>> > > params 00001000 00000500 00000000 --> status: Timed Out
>> > >
>> > > Success case takes about 400us to complete, see below trace(44.286278
>> > > - 44.285897 = 0.000381):
>> > >
>> > > configfs_acm.sh-822   [000] d..1    44.285896: dwc3_writel: addr
>> > > 000000006d59aae1 value 00000401
>> > > configfs_acm.sh-822   [000] d..1    44.285897: dwc3_readl: addr
>> > > 000000006d59aae1 value 00000401
>> > > ... ...
>> > > configfs_acm.sh-822   [000] d..1    44.286278: dwc3_readl: addr
>> > > 000000006d59aae1 value 00000001
>> > > configfs_acm.sh-822   [000] d..1    44.286279: dwc3_gadget_ep_cmd:
>> > > ep0out: cmd 'Set Endpoint Configuration' [401] params 00001000
>> > > 00000500 00000000 --> status: Successful
>> > >
>> > > Hi John,
>> > >
>> > > Do you still have this problem? if yes, What's the value of
>> > > USBLNKST[21:18] when the timeout happens?
>> >
>> > Sorry. As I mentioned, I was working to upstream a patchset that I
>> > hadn't created, so the context I had was limited. As I couldn't
>> > reproduce an issue without the change on the device I had, I figured
>> > it would be best to drop it.
>>
>> That was fine.
>> >
>> > However, as you have some analysis and rational for why such a change
>> > would be needed, I don't have an objection to it. Do you want to
>> > resubmit the patch with your explanation and detailed log above in the
>> > commit message?
>>
>> Sure, I will resubmit the patch with my explanation added in commit message.
>
> Hi John
>
> A second think of this, I feel use readl_poll_timeout_atomic() to wait by time
> is more proper here, so I create a new patch to address this also other
> registers polling, see below patch with you CCed:
>
> https://patchwork.kernel.org/patch/11536081/

Fixing a bug has nothing to do with using
readl_poll_timeout_atomic(). Please don't mix things as it just makes
review time consuming.

Let's find out what the bug is all about, only then should we consider
moving over to readl_poll_timeout_atomic().

-- 
balbi

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