[Intel-gfx] [v3 5/5] drm/i915/dsi: Read/write proper brightness value via MIPI DCS command

[Lee Shawn C]

Driver has to swap the endian before send brightness level value
to tcon.

v2: Use __be16 instead of u16 to fix sparse warning.
v3: Send one or two bytes brightness value depend on the precision.
v4: get data length of brightness value more easily.

Reported-by: kernel test robot <l...@intel.com>
Cc: Ville Syrjala <ville.syrj...@linux.intel.com>
Cc: Jani Nikula <jani.nik...@linux.intel.com>
Cc: Vandita Kulkarni <vandita.kulka...@intel.com>
Cc: Cooper Chiou <cooper.ch...@intel.com>
Cc: William Tseng <william.ts...@intel.com>
Signed-off-by: Lee Shawn C <shawn.c....@intel.com>
Reviewed-by: Jani Nikula <jani.nik...@intel.com>
---
 .../i915/display/intel_dsi_dcs_backlight.c    | 23 +++++++++++++------
 1 file changed, 16 insertions(+), 7 deletions(-)

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 567c086602d5..f61ed82e8867 100644
--- a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
@@ -47,33 +47,42 @@ static u32 dcs_get_backlight(struct intel_connector 
*connector, enum pipe unused
 {
        struct intel_encoder *encoder = intel_attached_encoder(connector);
        struct intel_dsi *intel_dsi = enc_to_intel_dsi(encoder);
+       struct intel_panel *panel = &connector->panel;
        struct mipi_dsi_device *dsi_device;
-       u8 data = 0;
+       u8 data[2] = {};
        enum port port;
+       size_t len = panel->backlight.max > U8_MAX ? 2 : 1;
 
-       /* FIXME: Need to take care of 16 bit brightness level */
        for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) {
                dsi_device = intel_dsi->dsi_hosts[port]->device;
                mipi_dsi_dcs_read(dsi_device, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
-                                 &data, sizeof(data));
+                                 &data, len);
                break;
        }
 
-       return data;
+       return (data[1] << 8) | data[0];
 }
 
 static void dcs_set_backlight(const struct drm_connector_state *conn_state, 
u32 level)
 {
        struct intel_dsi *intel_dsi = 
enc_to_intel_dsi(to_intel_encoder(conn_state->best_encoder));
+       struct intel_panel *panel = 
&to_intel_connector(conn_state->connector)->panel;
        struct mipi_dsi_device *dsi_device;
-       u8 data = level;
+       u8 data[2] = {};
        enum port port;
+       size_t len = panel->backlight.max > U8_MAX ? 2 : 1;
+
+       if (len == 1) {
+               data[0] = level;
+       } else {
+               data[0] = level >> 8;
+               data[1] = level;
+       }
 
-       /* FIXME: Need to take care of 16 bit brightness level */
        for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) {
                dsi_device = intel_dsi->dsi_hosts[port]->device;
                mipi_dsi_dcs_write(dsi_device, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
-                                  &data, sizeof(data));
+                                  &data, len);
        }
 }
 
-- 
2.17.1