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Message-ID: <9a64c685-9ff0-bc1d-e604-e3773ff9edd7@linaro.org>
Date:   Fri, 13 Jan 2023 10:57:18 +0200
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Subject: Re: [PATCH] drm/msm: Initialize mode_config earlier
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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To:     Bjorn Andersson <quic_bjorande@quicinc.com>,
        Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Johan Hovold <johan@kernel.org>
Cc:     Sean Paul <sean@poorly.run>, David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, linux-arm-msm@vger.kernel.org,
        dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
References: <20230113041051.4189063-1-quic_bjorande@quicinc.com>
 <eea1c5dc-6bc5-4246-f0e1-0c790de9f078@linaro.org>
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On 13/01/2023 06:23, Dmitry Baryshkov wrote:
> On 13/01/2023 06:10, Bjorn Andersson wrote:
>> Invoking drm_bridge_hpd_notify() on a drm_bridge with a HPD-enabled
>> bridge_connector ends up in drm_bridge_connector_hpd_cb() calling
>> drm_kms_helper_hotplug_event(), which assumes that the associated
>> drm_device's mode_config.funcs is a valid pointer.
>>
>> But in the MSM DisplayPort driver the HPD enablement happens at bind
>> time and mode_config.funcs is initialized late in msm_drm_init(). This
>> means that there's a window for hot plug events to dereference a NULL
>> mode_config.funcs.
>>
>> Move the assignment of mode_config.funcs before the bind, to avoid this
>> scenario.
> 
> Cam we make DP driver not to report HPD events until the enable_hpd() 
> was called? I think this is what was fixed by your internal_hpd patchset.

Or to express this in another words: I thought that internal_hpd already 
deferred enabling hpd event reporting till the time when we need it, 
didn't it?


-- 
With best wishes
Dmitry