linux-kernel - [PATCH v3 3/3] drm/panel-edp: Avoid adding multiple preferred modes

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Message-ID: <20231106202718.2770821-4-hsinyi@chromium.org>
Date:   Mon,  6 Nov 2023 12:22:50 -0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Sam Ravnborg <sam@...nborg.org>,
        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>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/3] drm/panel-edp: Avoid adding multiple preferred modes

If a non generic edp-panel is under aux-bus, the mode read from edid would
still be selected as preferred and results in multiple preferred modes,
which is ambiguous.

If both hard-coded mode and edid exists, only add mode from hard-coded.

Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
---
v2->v3: if hard-coded mode presents, don't add edid mode.
---
 drivers/gpu/drm/panel/panel-edp.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 0fb439b5efb1..54dbbdf62ec0 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -594,8 +594,20 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 				      p->detected_panel != ERR_PTR(-EINVAL) &&
 				      p->detected_panel->override_edid_mode;
 
-	/* probe EDID if a DDC bus is available */
-	if (p->ddc) {
+	/*
+	 * If both edid and hard-coded modes exists, only add hard-coded modes
+	 * to avoid multiple preferred modes.
+	 */
+	if (p->desc->num_timings || p->desc->num_modes) {
+		/*
+		 * Add hard-coded panel modes. Don't call this if there are no
+		 * timings and no modes (the generic edp-panel case) because it
+		 * will clobber the display_info that was already set by
+		 * drm_add_edid_modes().
+		 */
+		num += panel_edp_get_non_edid_modes(p, connector);
+	} else if (p->ddc) {
+		/* probe EDID if a DDC bus is available */
 		pm_runtime_get_sync(panel->dev);
 
 		if (!p->edid)
@@ -617,14 +629,7 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 		pm_runtime_put_autosuspend(panel->dev);
 	}
 
-	/*
-	 * Add hard-coded panel modes. Don't call this if there are no timings
-	 * and no modes (the generic edp-panel case) because it will clobber
-	 * the display_info that was already set by drm_add_edid_modes().
-	 */
-	if (p->desc->num_timings || p->desc->num_modes)
-		num += panel_edp_get_non_edid_modes(p, connector);
-	else if (!num)
+	if (!num)
 		dev_warn(p->base.dev, "No display modes\n");
 
 	/*
-- 
2.42.0.869.gea05f2083d-goog