linux-kernel - Re: [PATCH v2] drm/msm/dp: remove fail safe mode related code

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Date:   Tue, 26 Apr 2022 10:36:45 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>, <agross@...nel.org>,
        <airlied@...ux.ie>, <bjorn.andersson@...aro.org>,
        <daniel@...ll.ch>, <dmitry.baryshkov@...aro.org>,
        <robdclark@...il.com>, <sean@...rly.run>, <vkoul@...nel.org>
CC:     <quic_aravindh@...cinc.com>, <quic_sbillaka@...cinc.com>,
        <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/msm/dp: remove fail safe mode related code



On 4/25/2022 11:00 PM, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2022-04-25 22:56:35)
>> Current DP driver implementation has adding safe mode done at
>> dp_hpd_plug_handle() which is expected to be executed under event
>> thread context.
>>
>> However there is possible circular locking happen (see blow stack trace)
>> after edp driver call dp_hpd_plug_handle() from dp_bridge_enable() which
>> is executed under drm_thread context.
>>
>> After review all possibilities methods and as discussed on
>> https://patchwork.freedesktop.org/patch/483155/, supporting EDID
>> compliance tests in the driver is quite hacky. As seen with other
>> vendor drivers, supporting these will be much easier with IGT. Hence
>> removing all the related fail safe code for it so that no possibility
>> of circular lock will happen.
> [...]
>>
>> Changes in v2:
>> -- re text commit title
>> -- remove all fail safe mode
>>
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> 
> Should add some Fixes tags here, probably for the first introduction of
> this logic and the one that moved stuff around to try to avoid the
> lockdep warning.

Fixes: 8b2c181 ("drm/msm/dp: add fail safe mode outside of event_mutex 
context")