From c9d27c6be518b4ef2966d9564654ef99292ea1b3 Mon Sep 17 00:00:00 2001
From: Daniel Mentz <danielmentz@google.com>
Date: Mon, 16 Jan 2023 17:49:07 -0500
Subject: [PATCH] drm/mipi-dsi: Fix byte order of 16-bit DCS set/get brightness
Git-commit: c9d27c6be518b4ef2966d9564654ef99292ea1b3
Patch-mainline: v6.3-rc1
References: git-fixes

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.

Add new functions to properly handle 16-bit brightness in big endian,
since the two 8- and 16-bit cases are distinct from each other.

[richard: use separate functions instead of switch/case]
[richard: split into 16-bit component]

Fixes: 1a9d759331b8 ("drm/dsi: Implement DCS set/get display brightness")
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Link: https://android.googlesource.com/kernel/msm/+/754affd62d0ee268c686c53169b1dbb7deac8550
[richard: fix 16-bit brightness_get]
Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Tested-by: Caleb Connolly <caleb@connolly.tech>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230116224909.23884-2-mailingradian@gmail.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/drm_mipi_dsi.c |   52 +++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_mipi_dsi.h     |    4 +++
 2 files changed, 56 insertions(+)

--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -1143,6 +1143,58 @@ int mipi_dsi_dcs_get_display_brightness(
 }
 EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);
 
+/**
+ * mipi_dsi_dcs_set_display_brightness_large() - sets the 16-bit brightness value
+ *    of the display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 brightness)
+{
+	u8 payload[2] = { brightness >> 8, brightness & 0xff };
+	ssize_t err;
+
+	err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
+				 payload, sizeof(payload));
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness_large);
+
+/**
+ * mipi_dsi_dcs_get_display_brightness_large() - gets the current 16-bit
+ *    brightness value of the display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 *brightness)
+{
+	u8 brightness_be[2];
+	ssize_t err;
+
+	err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
+				brightness_be, sizeof(brightness_be));
+	if (err <= 0) {
+		if (err == 0)
+			err = -ENODATA;
+
+		return err;
+	}
+
+	*brightness = (brightness_be[0] << 8) | brightness_be[1];
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness_large);
+
 static int mipi_dsi_drv_probe(struct device *dev)
 {
 	struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -283,6 +283,10 @@ int mipi_dsi_dcs_set_display_brightness(
 					u16 brightness);
 int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
 					u16 *brightness);
+int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 brightness);
+int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
+					     u16 *brightness);
 
 /**
  * struct mipi_dsi_driver - DSI driver