From 6a9dfde7695e537f183bb6eb226f82faf7adb1ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 29 Sep 2021 21:45:36 +0300
Subject: drm/i915: Reject user modes that don't match fixed mode's refresh
rate
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Git-commit: f5b8c316092f2501ca32ac32f5c6303e2c58ef50
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
When using a panel with a fixed mode we don't change the refresh
rate of the display. Reject any user requested mode which doesn't
match that fixed refresh rate.
Unfortunately when Xorg sees the scaling_mode property on the
connecor it likes to automagically cook up modes whose refresh
rate is a fair bit off from the fixed refresh rate we use. So
we have to give it some extra latitude so that we don't start to
reject all of it.
v2: sDVO now uses intel_panel_compute_config() too
v3: Add a debug message to inform the user what happened
References: https://gitlab.freedesktop.org/drm/intel/-/issues/2939
References: https://gitlab.freedesktop.org/drm/intel/-/issues/3969
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210929184536.8332-1-ville.syrjala@linux.intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/display/intel_panel.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 77c1ca387de0..a0c8e43db5eb 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -53,6 +53,21 @@ int intel_panel_compute_config(struct intel_connector *connector,
if (!fixed_mode)
return 0;
+ /*
+ * We don't want to lie too much to the user about the refresh
+ * rate they're going to get. But we have to allow a bit of latitude
+ * for Xorg since it likes to automagically cook up modes with slightly
+ * off refresh rates.
+ */
+ if (abs(drm_mode_vrefresh(adjusted_mode) - drm_mode_vrefresh(fixed_mode)) > 1) {
+ drm_dbg_kms(connector->base.dev,
+ "[CONNECTOR:%d:%s] Requested mode vrefresh (%d Hz) does not match fixed mode vrefresh (%d Hz)\n",
+ connector->base.base.id, connector->base.name,
+ drm_mode_vrefresh(adjusted_mode), drm_mode_vrefresh(fixed_mode));
+
+ return -EINVAL;
+ }
+
drm_mode_copy(adjusted_mode, fixed_mode);
drm_mode_set_crtcinfo(adjusted_mode, 0);
--
2.38.1