[Intel-gfx] [PATCH v3] drm/i915/dsi: transmit brightness command in HS state

[William Tseng <william.tseng@intel.com>]

In Video Mode, if DSI transcoder is set to transmit packets
in LP Escape mode, screen flickering would be obseved when
brightness commands are continuously and quickly transmitted
to a panel.

The problem may be resolved by changing the mode to transmit
packets from Low Power to HS.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Signed-off-by: William Tseng <william.tseng@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
index f61ed82e8867..7d234429e71e 100644
--- a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
@@ -71,6 +71,7 @@ static void dcs_set_backlight(const struct drm_connector_state *conn_state, u32
 	u8 data[2] = {};
 	enum port port;
 	size_t len = panel->backlight.max > U8_MAX ? 2 : 1;
+	unsigned long mode_flags;
 
 	if (len == 1) {
 		data[0] = level;
@@ -81,8 +82,11 @@ static void dcs_set_backlight(const struct drm_connector_state *conn_state, u32
 
 	for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) {
 		dsi_device = intel_dsi->dsi_hosts[port]->device;
+		mode_flags = dsi_device->mode_flags;
+		dsi_device->mode_flags &= ~MIPI_DSI_MODE_LPM;
 		mipi_dsi_dcs_write(dsi_device, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
 				   &data, len);
+		dsi_device->mode_flags = mode_flags;
 	}
 }
 
-- 
2.17.1