[PATCH 2/4] drm/i915/dsi: Enable dithering for 6 bpc panels

[Hans de Goede]

The display engine has 2 dithering enable bits which both need to be set
for dithering to happen, 1 in the PIPECONF register which is taken care of
by i9xx_set_pipeconf() and a second bit at the encoder level.

The dsi code was not setting the encoder level dithering enable bit causing
dithering to be disabled, this commit fixes this.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/gpu/drm/i915/vlv_dsi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/vlv_dsi.c b/drivers/gpu/drm/i915/vlv_dsi.c
index c10def5efa22..c21cbfa9653c 100644
--- a/drivers/gpu/drm/i915/vlv_dsi.c
+++ b/drivers/gpu/drm/i915/vlv_dsi.c
@@ -711,6 +711,10 @@ static void intel_dsi_port_enable(struct intel_encoder *encoder,
 					LANE_CONFIGURATION_DUAL_LINK_B :
 					LANE_CONFIGURATION_DUAL_LINK_A;
 		}
+
+		if (intel_dsi->pixel_format != MIPI_DSI_FMT_RGB888)
+			temp |= DITHERING_ENABLE;
+
 		/* assert ip_tg_enable signal */
 		I915_WRITE(port_ctrl, temp | DPI_ENABLE);
 		POSTING_READ(port_ctrl);
-- 
2.19.1