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

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Date:   Wed, 06 Oct 2021 08:37:45 -0700
From:   khsieh@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.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 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.

>> 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.
>> 
>> 
>>