drm/i915: Allow DBLSCAN user modes with eDP/LVDS/DSI

When encountering a connector with the scaling mode property both
intel and modesetting ddxs sometimes add tons of DBLSCAN modes
to the output's mode list. The idea presumably being that since the
output will be going through the panel fitter anyway we can pretend
to use any kind of mode.

Sadly that means we can't reject user modes with the DBLSCAN flag
until we know whether we're going to be using the panel's native
mode or the user mode directly. Doing otherwise means X clients using
xf86vidmode/xrandr will get a protocol error (and often self
terminate as a result) when the kernel refuses to use the requested
mode with the DBLSCAN flag.

To undo the regression we'll move the DBLSCAN checks into the
connector->mode_valid() and encoder->compute_config() hooks.

Cc: stable@vger.kernel.org
Cc: Vito Caputo <vcaputo@pengaru.com>
Reported-by: Vito Caputo <vcaputo@pengaru.com>
Fixes: e995ca0b8139 ("drm/i915: Provide a device level .mode_valid() hook")
References: https://lkml.org/lkml/2018/5/21/715
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180524125403.23445-1-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106804
Tested-by: Arkadiusz Miskiewicz <arekm@maven.pl>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 211d601cd1b1..95aa29cf2d9c 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -304,6 +304,9 @@ intel_crt_mode_valid(struct drm_connector *connector,
 	int max_dotclk = dev_priv->max_dotclk_freq;
 	int max_clock;
 
+	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
+		return MODE_NO_DBLESCAN;
+
 	if (mode->clock < 25000)
 		return MODE_CLOCK_LOW;
 
@@ -337,6 +340,12 @@ static bool intel_crt_compute_config(struct intel_encoder *encoder,
 				     struct intel_crtc_state *pipe_config,
 				     struct drm_connector_state *conn_state)
 {
+	struct drm_display_mode *adjusted_mode =
+		&pipe_config->base.adjusted_mode;
+
+	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
+		return false;
+
 	return true;
 }
 
@@ -344,6 +353,12 @@ static bool pch_crt_compute_config(struct intel_encoder *encoder,
 				   struct intel_crtc_state *pipe_config,
 				   struct drm_connector_state *conn_state)
 {
+	struct drm_display_mode *adjusted_mode =
+		&pipe_config->base.adjusted_mode;
+
+	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
+		return false;
+
 	pipe_config->has_pch_encoder = true;
 
 	return true;
@@ -354,6 +369,11 @@ static bool hsw_crt_compute_config(struct intel_encoder *encoder,
 				   struct drm_connector_state *conn_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct drm_display_mode *adjusted_mode =
+		&pipe_config->base.adjusted_mode;
+
+	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
+		return false;
 
 	pipe_config->has_pch_encoder = true;