linux-kernel - Re: [PATCH v3 09/12] drm/msm/dp: HPD handling relates to next

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Message-ID: <5974CB5A-699F-4768-9DAA-FAE507CFAD53@linaro.org>
Date:   Wed, 26 Oct 2022 09:08:49 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
CC:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Johan Hovold <johan@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/12] drm/msm/dp: HPD handling relates to next_bridge



On 26 October 2022 06:26:21 EEST, Bjorn Andersson <quic_bjorande@...cinc.com> wrote:
>From: Bjorn Andersson <bjorn.andersson@...aro.org>
>
>The DisplayPort controller's internal HPD interrupt handling is used for
>cases where the HPD signal is connected to a GPIO which is pinmuxed into
>the DisplayPort controller.
>
>Most of the logic for enabling and disabling the HPD-related interrupts
>is conditioned on the presence of an EDP panel, but more generically
>designs that has a downstream drm_bridge (next_bridge) could use this to
>handle the HPD interrupts, instead of the internal mechanism.
>
>So replace the current is_edp-based guards with a check for the presence
>of next_bridge.

This does not sound correct. The next bridge might be a dummy bridge, not supporting the hpd. Please change this to use the enable_hpd()/disable_hpd() callbacks. This way the drm_bridge_connector framework will make sure to enable hpd handling for the bridge that is actually supposed to generate hpd events.


>
>Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
>---
>
>Changes since v2:
>- None


-- 
With best wishes
Dmitry