disp: msm: limit display brightness max cooling device level

Based on panel hardware support, display brightness levels can
be very high value. This high value display brightness cooling
device levels can cause exceeding PAGE_SIZE for cooling device stat
buffer. It leads to buffer failure for cooling device stat feature.

Limit display panel mitigation level max to 255. If hardware
supports more than 255, then scale brightness levels fit
into above limit.

Change-Id: Ieeee4ff2aa5cd884819b30b4fd9839e48ac4d804
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>

msm/msm_cooling_device.c

@@ -1,17 +1,19 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (c) 2020, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2020-2021 The Linux Foundation. All rights reserved.
  */
 #include <linux/err.h>
 #include <linux/slab.h>
 #include "msm_cooling_device.h"
 
+#define BRIGHTNESS_CDEV_MAX 255
+
 static int sde_cdev_get_max_brightness(struct thermal_cooling_device *cdev,
 					unsigned long *state)
 {
 	struct sde_cdev *disp_cdev = (struct sde_cdev *)cdev->devdata;
 
-	*state = disp_cdev->bd->props.max_brightness;
+	*state = disp_cdev->bd->props.max_brightness / disp_cdev->cdev_sf;
 
 	return 0;
 }
@@ -21,7 +23,8 @@ static int sde_cdev_get_cur_brightness(struct thermal_cooling_device *cdev,
 {
 	struct sde_cdev *disp_cdev = (struct sde_cdev *)cdev->devdata;
 
-	*state = disp_cdev->bd->props.max_brightness - disp_cdev->thermal_state;
+	*state = ((disp_cdev->bd->props.max_brightness -
+			disp_cdev->thermal_state) / disp_cdev->cdev_sf);
 
 	return 0;
 }
@@ -32,10 +35,11 @@ static int sde_cdev_set_cur_brightness(struct thermal_cooling_device *cdev,
 	struct sde_cdev *disp_cdev = (struct sde_cdev *)cdev->devdata;
 	unsigned long brightness_lvl = 0;
 
-	if (state > disp_cdev->bd->props.max_brightness)
+	if (state > disp_cdev->bd->props.max_brightness / disp_cdev->cdev_sf)
 		return -EINVAL;
 
-	brightness_lvl = disp_cdev->bd->props.max_brightness - state;
+	brightness_lvl = disp_cdev->bd->props.max_brightness -
+				(state * disp_cdev->cdev_sf);
 	if (brightness_lvl == disp_cdev->thermal_state)
 		return 0;
 	disp_cdev->thermal_state = brightness_lvl;
@@ -67,6 +71,13 @@ struct sde_cdev *backlight_cdev_register(struct device *dev,
 		return ERR_PTR(-ENOMEM);
 	disp_cdev->thermal_state = 0;
 	disp_cdev->bd = bd;
+
+	if (bd->props.max_brightness > BRIGHTNESS_CDEV_MAX)
+		disp_cdev->cdev_sf = (bd->props.max_brightness /
+						BRIGHTNESS_CDEV_MAX);
+	else
+		disp_cdev->cdev_sf = 1;
+
 	disp_cdev->cdev = thermal_of_cooling_device_register(dev->of_node,
 				(char *)dev_name(&bd->dev), disp_cdev,
 				&sde_cdev_ops);

msm/msm_cooling_device.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
- * Copyright (c) 2020, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2020-2021 The Linux Foundation. All rights reserved.
  */
 
 #ifndef __SDE_THERMAL_CORE_H__
@@ -16,6 +16,7 @@ struct sde_cdev {
 	struct thermal_cooling_device *cdev;
 	struct backlight_device *bd;
 	unsigned long thermal_state;
+	unsigned int cdev_sf;
 };
 
 #ifdef CONFIG_THERMAL_OF