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

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Message-ID: <YV0FlTyMEzlyNsN9@ripper>
Date:   Tue, 5 Oct 2021 19:10:29 -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 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

> I had prepared a patch (drm/msm/dp: do not initialize combo phy until plugin
> interrupt) to fix this problem.
> Unfortunately, my patch is depend on Bjorn's patch (PATCH v3 3/5]
> drm/msm/dp: Support up to 3 DP controllers).
> I will submit my patch for review once Bjorn's patches merged in.
> Therefore I would think this patch should go after both Bjorn's patches and
> my patch.
> 
> 
>