linux-kernel - [PATCH 3/3] drm/panel-edp: Choose correct preferred mode

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Date:   Wed,  1 Nov 2023 14:20:11 -0700
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 3/3] drm/panel-edp: Choose correct preferred mode

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 a hard-coded mode is present, unset the preferred bit of the modes read
from edid.

Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
---
 drivers/gpu/drm/drm_modes.c       | 16 ++++++++++++++++
 drivers/gpu/drm/panel/panel-edp.c |  7 +++++--
 include/drm/drm_modes.h           |  1 +
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index ac9a406250c5..35927467f4b0 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1933,6 +1933,22 @@ void drm_connector_list_update(struct drm_connector *connector)
 }
 EXPORT_SYMBOL(drm_connector_list_update);
 
+/**
+ * drm_mode_unset_preferred - clear the preferred status on existing modes.
+ * @connector: the connector to update
+ *
+ * Walk the mode list for connector, clearing the preferred status on existing
+ * modes.
+ */
+void drm_mode_unset_preferred_modes(struct drm_connector *connector)
+{
+	struct drm_display_mode *cur_mode;
+
+	list_for_each_entry(cur_mode, &connector->probed_modes, head)
+		cur_mode->type &= ~DRM_MODE_TYPE_PREFERRED;
+}
+EXPORT_SYMBOL_GPL(drm_mode_unset_preferred_modes);
+
 static int drm_mode_parse_cmdline_bpp(const char *str, char **end_ptr,
 				      struct drm_cmdline_mode *mode)
 {
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 0883ff312eba..b3ac473b2554 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -622,10 +622,13 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 	 * 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)
+	if (p->desc->num_timings || p->desc->num_modes) {
+		/* hard-coded modes present, unset preferred modes from edid. */
+		drm_mode_unset_preferred_modes(connector);
 		num += panel_edp_get_non_edid_modes(p, connector);
-	else if (!num)
+	} else if (!num) {
 		dev_warn(p->base.dev, "No display modes\n");
+	}
 
 	/*
 	 * TODO: Remove once all drm drivers call
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index c613f0abe9dc..301817e00a15 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -560,6 +560,7 @@ void drm_mode_prune_invalid(struct drm_device *dev,
 			    struct list_head *mode_list, bool verbose);
 void drm_mode_sort(struct list_head *mode_list);
 void drm_connector_list_update(struct drm_connector *connector);
+void drm_mode_unset_preferred_modes(struct drm_connector *connector);
 
 /* parsing cmdline modes */
 bool
-- 
2.42.0.869.gea05f2083d-goog