linux-kernel - Re: [PATCH v2 06/10] drm/msm/dp: fix aux-bus EP lifetime

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Date:   Tue, 13 Sep 2022 13:36:09 +0100
From:   Doug Anderson <dianders@...omium.org>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Steev Klimaszewski <steev@...i.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 06/10] drm/msm/dp: fix aux-bus EP lifetime

Hi,

On Tue, Sep 13, 2022 at 9:58 AM Johan Hovold <johan+linaro@...nel.org> wrote:
>
> Device-managed resources allocated post component bind must be tied to
> the lifetime of the aggregate DRM device or they will not necessarily be
> released when binding of the aggregate device is deferred.
>
> This can lead resource leaks or failure to bind the aggregate device
> when binding is later retried and a second attempt to allocate the
> resources is made.
>
> For the DP aux-bus, an attempt to populate the bus a second time will
> simply fail ("DP AUX EP device already populated").
>
> Fix this by tying the lifetime of the EP device to the DRM device rather
> than DP controller platform device.
>
> Fixes: c3bf8e21b38a ("drm/msm/dp: Add eDP support via aux_bus")
> Cc: stable@...r.kernel.org      # 5.19
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

This seems fine to me as a short term fix until we get the DP AUX
populating moved to probe.

Reviewed-by: Douglas Anderson <dianders@...omium.org>