linux-kernel - Re: [PATCH] drm/msm/dp: Shorten SETUP timeout

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Message-ID: <YWR0rrC4yoKtXXTL@ripper>
Date:   Mon, 11 Oct 2021 10:30:22 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     khsieh@...eaurora.org
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Sankeerth Billakanti <sbillaka@...eaurora.org>
Subject: Re: [PATCH] drm/msm/dp: Shorten SETUP timeout

On Mon 11 Oct 08:24 PDT 2021, khsieh@...eaurora.org wrote:

> On 2021-10-08 09:44, Bjorn Andersson wrote:
> > On Fri 08 Oct 09:07 PDT 2021, khsieh@...eaurora.org wrote:
> > 
> > > On 2021-10-07 15:34, Stephen Boyd wrote:
> > > > Quoting khsieh@...eaurora.org (2021-10-07 13:28:12)
> > > > > On 2021-10-07 13:06, Bjorn Andersson wrote:
> > > > > > On Thu 07 Oct 12:51 PDT 2021, khsieh@...eaurora.org wrote:
> > > > > >
> > > > > >> On 2021-10-06 10:31, Bjorn Andersson wrote:
> > > > > >> > On Wed 06 Oct 08:37 PDT 2021, khsieh@...eaurora.org wrote:
> > > > > >> >
> > > > > >> > > On 2021-10-05 19:10, Bjorn Andersson wrote:
> > > > > >> > > > On Tue 05 Oct 16:04 PDT 2021, khsieh@...eaurora.org wrote:
> > > > > >> > > >
> > > > > >> > > > > On 2021-10-05 15:36, Stephen Boyd wrote:
> > > > > >> > > > > > Quoting Bjorn Andersson (2021-10-05 14:40:38)
> > > > > >> > > > > > > On Tue 05 Oct 11:45 PDT 2021, Stephen Boyd wrote:
> > > > > >> > > > > > >
> > > > > >> > > > > > > > Quoting Bjorn Andersson (2021-10-04 19:37:50)
> > > > > >> > > > > > > > > Found in the middle of a patch from Sankeerth was the reduction of the
> > > > > >> > > > > > > > > INIT_SETUP timeout from 10s to 100ms. Upon INIT_SETUP timeout the host
> > > > > >> > > > > > > > > is initalized and HPD interrupt start to be serviced, so in the case of
> > > > > >> > > > > > > > > eDP this reduction improves the user experience dramatically - i.e.
> > > > > >> > > > > > > > > removes 9.9s of bland screen time at boot.
> > > > > >> > > > > > > > >
> > > > > >> > > > > > > > > Suggested-by: Sankeerth Billakanti <sbillaka@...eaurora.org>
> > > > > >> > > > > > > > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > > > >> > > > > > > > > ---
> > > > > >> > > > > > > >
> > > > > >> > > > > > > > Any Fixes tag? BTW, the delay design is pretty convoluted. I had to go
> > > > > >> > > > > > > > re-read the code a couple times to understand that it's waiting 100ms
> > > > > >> > > > > > > > times the 'delay' number. Whaaaaat?
> > > > > >> > > > > > > >
> > > > > >> > > > > > >
> > > > > >> > > > > > > I assume you're happy with the current 10s delay on the current
> > > > > >> > > > > > > devices, so I don't think we should push for this to be backported.
> > > > > >> > > > > > > I have no need for it to be backported on my side at least.
> > > > > >> > > > > > >
> > > > > >> > > > > >
> > > > > >> > > > > > Sure. Fixes tag != backported to stable trees but it is close.
> > > > > >> > > > > >
> > > > > >> > > > > > > > Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> > > > > >> > > > > > >
> > > > > >> > > > >   dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 1); <== to 100ms
> > > > > >> > > > >
> > > > > >> > > > > This patch will prevent usb3 from working due to dp driver
> > > > > >> > > > > initialize phy
> > > > > >> > > > > earlier than usb3 which cause timeout error at power up usb3 phy
> > > > > >> > > > > when both
> > > > > >> > > > > edp and dp are enabled.
> > > > > >> > > >
> > > > > >> > > > Can you please help me understand what you mean here, I use this on my
> > > > > >> > > > sc8180x with both eDP and USB-C/DP right now. What is it that doesn't
> > > > > >> > > > work? Or am I just lucky in some race condition?
> > > > > >> > > >
> > > > > >> > > > Thanks,
> > > > > >> > > > Bjorn
> > > > > >> > > >
> > > > > >> > > The problem is seen at sc7280.
> > > > > >> > > Apple dongle have both  hdmi and usb port.
> > > > > >> > > plug Apple dongle into type-c, then plug DP into apple's hdmi port
> > > > > >> > > and usb
> > > > > >> > > mouse into apple's usb port.
> > > > > >> > > If edp enabled at this time, then usb mouse will not work due to
> > > > > >> > > timeout at
> > > > > >> > > phy power up.
> > > > > >> > >
> > > > > >> >
> > > > > >> > Okay, so you're saying that if the DP driver invokes phy_power_on()
> > > > > >> > before the USB driver does, USB initialization fails (or at least USB
> > > > > >> > doesn't work)?
> > > > > >>
> > > > > >> if dp driver call qcom_qmp_phy_init() before usb3 call
> > > > > >> qcom_qmp_phy_init(),
> > > > > >> usb3 driver will timeout at readl_poll_timeout(status, val, (val &
> > > > > >> mask) ==
> > > > > >> ready, 10, PHY_INIT_COMPLETE_TIMEOUT) of qcom_qmp_phy_power_on().
> > > > > >
> > > > > > Thanks, I will try to reproduce this on my side. So the 10 seconds here
> > > > > > is strictly to give good enough time for the dwc3 driver to probe...
> > > > > >
> > > > > > Any idea why you're saying that this is specific to sc7280, what
> > > > > > changed
> > > > > > from sc7180?
> > > > >
> > > > > I did not have sc7180 with edp before so that i am not sure it will
> > > > > happen on sc7180 or not.
> > > > > The usb3 does not work when both edp and dp enabled I just seen at
> > > > > sc7280.
> > > > > Current at sc7280 EC is not boot up correctly when system power up.
> > > > > I have to manual reboot EC from linux kernel shell before DP/usb3 can
> > > > > work.
> > > > > I am not sure this contribute to this problem or not.
> > > > >
> > > >
> > > > Can you make the usb driver into a module and only load that module
> > > > later in boot after the DP driver calls qcom_qmp_phy_init()? That would
> > > > be an easy way to move usb probe after DP probe and expose this problem.
> > > 
> > > we need usb calls qcom_qmp_phy_init() before dp.
> > 
> > Why?
> I do not know the details.
> But I did see below scenario,
> 
> if dp driver call qcom_qmp_phy_init() before usb3 call
> qcom_qmp_phy_init(),
> usb3 driver will timeout at readl_poll_timeout(status, val, (val &
> mask) ==
> ready, 10, PHY_INIT_COMPLETE_TIMEOUT) of qcom_qmp_phy_power_on().

Sounds like a bug in the QMP driver, something that could easily be
reproduced by waiting for DP to be up before we bring up USB - either by
chance, or following Stephen's suggestion on purpose.

Someone will have to look into this, so that we don't need a 10 second
workaround in the (e)DP driver.

Regards,
Bjorn