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

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Date:   Thu, 07 Oct 2021 12:51:48 -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 2021-10-06 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().
> 
> Sounds like something we need to work out in the QMP phy driver. Do you
> have any more details about what's going wrong.
> 
> 
> Also, I've seen various references to said "Apple dongle", do you have 
> a
> link to the exact one you're testing with so I can pick one up for
> testing purposes as well?

Apple A2119 hdmi+usb dongle.
https://www.amazon.com/Apple-USB-C-Digital-Multiport-Adapter/dp/B07WF96FY5/ref=sr_1_2?dchild=1&keywords=apple+a2119&qid=1633636227&sr=8-2

> 
> Regards,
> 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.
>> > >
>> > >
>> > >