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

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Message-ID: <20221215170359.92422-1-mrodin@de.adit-jv.com>
Date:   Thu, 15 Dec 2022 18:03:59 +0100
From:   Michael Rodin <mrodin@...adit-jv.com>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        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>
CC:     Michael Rodin <mrodin@...adit-jv.com>, <michael@...in.online>,
        <erosca@...adit-jv.com>, <laurent.pinchart@...asonboard.com>
Subject: [PATCH] drm: override detected status for connectors which are forced on

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>
---
 drivers/gpu/drm/drm_probe_helper.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index bcd9611dabfd..0a3b8223c87a 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -304,6 +304,12 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
 	if (WARN_ON(ret < 0))
 		ret = connector_status_unknown;
 
+	if (connector->force == DRM_FORCE_ON ||
+	    connector->force == DRM_FORCE_ON_DIGITAL)
+		ret = connector_status_connected;
+	else if (connector->force == DRM_FORCE_OFF)
+		ret = connector_status_disconnected;
+
 	if (ret != connector->status)
 		connector->epoch_counter += 1;
 
@@ -346,6 +352,12 @@ drm_helper_probe_detect(struct drm_connector *connector,
 	else
 		ret = connector_status_connected;
 
+	if (connector->force == DRM_FORCE_ON ||
+	    connector->force == DRM_FORCE_ON_DIGITAL)
+		ret = connector_status_connected;
+	else if (connector->force == DRM_FORCE_OFF)
+		ret = connector_status_disconnected;
+
 	if (ret != connector->status)
 		connector->epoch_counter += 1;
 
-- 
2.25.1