ANDROID: drm/dsi: Fix byte order of DCS set/get brightness

The MIPI DCS specification demands that brightness values are sent in
big endian byte order. It also states that one parameter (i.e. one byte)
shall be sent/received for 8 bit wide values, and two parameters shall
be used for values that are between 9 and 16 bits wide.

Bug: 139263611
Bug: 139107810
Change-Id: I24306e21ec6a5ff48ea121d977419a81d5b44152
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Signed-off-by: Wilson Sung <wilsonsung@google.com>
(cherry picked from commit 3c373bfd83fd686390ea60a032ff876242c71d49)
Signed-off-by: Saravana Kannan <saravanak@google.com>

drivers/gpu/drm/drm_mipi_dsi.c

@@ -1052,17 +1052,33 @@ EXPORT_SYMBOL(mipi_dsi_dcs_set_tear_scanline);
  *    display
  * @dsi: DSI peripheral device
  * @brightness: brightness value
+ * @num_params: Number of parameters (bytes) to encode brightness value in. The
+ *              MIPI specification states that one parameter shall be sent for
+ *              devices that support 8-bit brightness levels. For devices that
+ *              support brightness levels wider than 8-bit, two parameters
+ *              shall be sent.
  *
  * Return: 0 on success or a negative error code on failure.
  */
 int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
-					u16 brightness)
+					u16 brightness, size_t num_params)
 {
-	u8 payload[2] = { brightness & 0xff, brightness >> 8 };
+	u8 payload[2];
 	ssize_t err;
 
+	switch (num_params) {
+	case 1:
+		payload[0] = brightness & 0xff;
+		break;
+	case 2:
+		payload[0] = brightness >> 8;
+		payload[1] = brightness & 0xff;
+		break;
+	default:
+		return -EINVAL;
+	}
 	err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
-				 payload, sizeof(payload));
+				 payload, num_params);
 	if (err < 0)
 		return err;
 
@@ -1075,16 +1091,25 @@ EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness);
  *    of the display
  * @dsi: DSI peripheral device
  * @brightness: brightness value
+ * @num_params: Number of parameters (i.e. bytes) the brightness value is
+ *              encoded in. The MIPI specification states that one parameter
+ *              shall be returned from devices that support 8-bit brightness
+ *              levels. Devices that support brightness levels wider than
+ *              8-bit return two parameters (i.e. bytes).
  *
  * Return: 0 on success or a negative error code on failure.
  */
 int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
-					u16 *brightness)
+					u16 *brightness, size_t num_params)
 {
+	u8 payload[2];
 	ssize_t err;
 
+	if (!(num_params == 1 || num_params == 2))
+		return -EINVAL;
+
 	err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
-				brightness, sizeof(*brightness));
+				payload, num_params);
 	if (err <= 0) {
 		if (err == 0)
 			err = -ENODATA;
@@ -1092,6 +1117,15 @@ int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
 		return err;
 	}
 
+	switch (num_params) {
+	case 1:
+		*brightness = payload[0];
+		break;
+	case 2:
+		*brightness = payload[0] << 8 || payload[1];
+		break;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);

drivers/gpu/drm/panel/panel-jdi-lt070me05000.c

@@ -341,7 +341,7 @@ static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
 
 	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
-	ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness);
+	ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness, 1);
 	if (ret < 0)
 		return ret;
 
@@ -357,7 +357,7 @@ static int dsi_dcs_bl_update_status(struct backlight_device *bl)
 
 	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
-	ret = mipi_dsi_dcs_set_display_brightness(dsi, bl->props.brightness);
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, bl->props.brightness, 1);
 	if (ret < 0)
 		return ret;
 

drivers/gpu/drm/panel/panel-samsung-s6e63j0x03.c

@@ -365,7 +365,7 @@ static int s6e63j0x03_enable(struct drm_panel *panel)
 		return ret;
 
 	/* set default white brightness */
-	ret = mipi_dsi_dcs_set_display_brightness(dsi, 0x00ff);
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, 0x00ff, 1);
 	if (ret < 0)
 		return ret;
 

include/drm/drm_mipi_dsi.h

@@ -283,9 +283,9 @@ int mipi_dsi_dcs_set_tear_on(struct mipi_dsi_device *dsi,
 int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format);
 int mipi_dsi_dcs_set_tear_scanline(struct mipi_dsi_device *dsi, u16 scanline);
 int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
-					u16 brightness);
+					u16 brightness, size_t num_params);
 int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
-					u16 *brightness);
+					u16 *brightness, size_t num_params);
 
 /**
  * struct mipi_dsi_driver - DSI driver