linux-kernel - Re: [PATCH] drm: override detected status for connectors which are forced on

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Message-ID: <20221222174054.tsj4rfzejrl3cc7g@penduick>
Date:   Thu, 22 Dec 2022 18:40:54 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Michael Rodin <mrodin@...adit-jv.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Airlie <airlied@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        michael@...in.online, erosca@...adit-jv.com,
        laurent.pinchart@...asonboard.com
Subject: Re: [PATCH] drm: override detected status for connectors which are
 forced on

Hi,

On Thu, Dec 15, 2022 at 06:03:59PM +0100, Michael Rodin wrote:
> The detected status of a connector should be ignored when a connector is
> forced as hinted in the commit d50ba256b5f1 ("drm/kms: start
> adding command line interface using fb."). One negative side effect of
> not ignoring this is observed on the RCar3 SoCs which use the dw-hdmi
> driver. It continues executing drm_helper_hpd_irq_event even if its
> connector is forced to ON. As consequence drm_helper_hpd_irq_event calls
> "detect" so the connector status is updated to "disconnected":
> 
> [  420.201527] [drm:drm_helper_hpd_irq_event] [CONNECTOR:76:HDMI-A-1] status updated from connected to disconnected
> 
> This status is corrected by drm_helper_probe_single_connector_modes shortly
> after this because this function checks if a connector is forced:
> 
> [  420.218703] [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:76:HDMI-A-1] status updated from disconnected to connected
> 
> To avoid similar issues this commit adapts functions which call "detect"
> so they check additionally if a connector is forced and override the status
> returned by "detect".
> 
> Fixes: 816da85a0990 ("drm: handle HPD and polled connectors separately")
> Signed-off-by: Michael Rodin <mrodin@...adit-jv.com>

As reported here, this breaks vc4, and probably i915:
https://lore.kernel.org/dri-devel/20221107123657.24vbgep3jqeklb2s@houat/

Maxime

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