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

From: Maxime Ripard <maxime@cerno.tech>
To: Michael Rodin <mrodin@de.adit-jv.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
	michael@rodin.online, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	laurent.pinchart@ideasonboard.com,
	Alex Deucher <alexander.deucher@amd.com>,
	Dave Airlie <airlied@redhat.com>,
	erosca@de.adit-jv.com
Subject: Re: [PATCH] drm: override detected status for connectors which are forced on
Date: Thu, 22 Dec 2022 18:40:54 +0100	[thread overview]
Message-ID: <20221222174054.tsj4rfzejrl3cc7g@penduick> (raw)
In-Reply-To: <20221215170359.92422-1-mrodin@de.adit-jv.com>

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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@de.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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