linux-kernel - Re: [PATCH v9 2/4] drm/msm/dp: Support only IRQ

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Date:   Fri, 22 Apr 2022 10:35:13 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>
CC:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        quic_kalyant <quic_kalyant@...cinc.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        quic_vproddut <quic_vproddut@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Sean Paul <sean@...rly.run>, Sean Paul <seanpaul@...omium.org>,
        Steev Klimaszewski <steev@...i.org>,
        "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [PATCH v9 2/4] drm/msm/dp: Support only IRQ_HPD and REPLUG
 interrupts for eDP

Hi Doug

On 4/22/2022 9:10 AM, Doug Anderson wrote:
> Hi,
> 
> On Fri, Apr 22, 2022 at 9:05 AM Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>>
>> Hi Doug
>>
>> For the lockdep error, the splat looks similar to what kuogee fixed
>> recently.
>>
>> Can you please check if below patch is present in your tree?
>>
>> https://patchwork.freedesktop.org/patch/481396/
> 
> Indeed I did have that in my tree already, but the lockdep splat is
> still there. I think the problem is that we're now calling
> dp_hpd_plug_handle() directly in dp_bridge_enable()
> 
> -Doug

Yes, now i understood this particular issue better and not sure how this 
wasn't caught. Perhaps some difference in the USE flags. Sankeerth didnt 
have lockdebug and thats why didnt hit this.

I have discussed with kuogee about why this change is needed and why 
this wasnt being done in get_modes().

It seems like originally, this was done for a quirk in the DP compliance 
equipment that it did not publish the fail safe mode ( even though some 
other modes were present ). Typically, any sink (as long as EDID read 
went through ) adds the 640x480 fail safe mode.

We could have done it in get_modes() even earlier but not sure how it 
was missed or was there some other reason.

Nonetheless, kuogee will post the change to move this to get_modes() 
shortly.

Thanks

Abhinav