feat(core): Add max backlight limit to backlight driver. [no changelog]

core/embed/io/backlight/inc/io/backlight.h

@@ -19,6 +19,9 @@
 
 #pragma once
 
+#define BACKLIGHT_MAX_LEVEL 255
+#define BACKLIGHT_MIN_LEVEL 0
+
 // Action to be taken when initializing or
 // deinitializing the backlight driver
 typedef enum {
@@ -41,7 +44,8 @@ void backlight_init(backlight_action_t action);
 // is kept on.
 void backlight_deinit(backlight_action_t action);
 
-// Sets the backlight level in range 0-255 and returns the actual level set.
+// Request the backlight level in range 0-255 and returns the actual level set.
+// The requested level may be limited if its above the max_level limit.
 //
 // If the level is outside the range, the function has no effect
 // and just returns the actual level set. If the backlight driver
@@ -52,3 +56,8 @@ int backlight_set(int val);
 //
 // Returns 0 if the backlight driver is not initialized.
 int backlight_get(void);
+
+// Set maximal backlight limit, limits the requested level to max_level value.
+//
+// Returns 0 if the backlight driver is not initialized.
+int backlight_set_max_level(int max_level);

core/embed/io/backlight/stm32u5/tps61062.c

@@ -47,11 +47,17 @@
 typedef struct {
   // Set if driver is initialized
   bool initialized;
+
   // Level requested (0-255)
+  int requested_level;
   int current_level;
+
   // Current step in range 0-32
   int current_step;
 
+  // Max backlight level
+  int max_level;
+
   DMA_HandleTypeDef dma;
   TIM_HandleTypeDef tim;
 
@@ -150,6 +156,10 @@ void backlight_init(backlight_action_t action) {
   HAL_TIM_Base_Start(&drv->tim);
   HAL_TIM_PWM_Start(&drv->tim, TIM_CHANNEL_1);
 
+  // Default no backlight max_level limit
+  drv->max_level = BACKLIGHT_MAX_LEVEL;
+  drv->requested_level = BACKLIGHT_MIN_LEVEL;
+
   drv->initialized = true;
 }
 
@@ -186,16 +196,28 @@ int backlight_set(int val) {
     return 0;
   }
 
-  if (val < 0 || val > 255) {
+  // Requested level out of range
+  if (val < BACKLIGHT_MIN_LEVEL || val > BACKLIGHT_MAX_LEVEL) {
     return drv->current_level;
   }
 
-  if (val == drv->current_level) {
+  // Capture requested level.
-    return val;
+  drv->requested_level = val;
+
+  int requested_level_limited = drv->requested_level;
+  if (drv->requested_level > drv->max_level) {
+    requested_level_limited = drv->max_level;
   }
 
-  drv->current_level = val;
+  // No action required
-  int set_step = MAX_STEPS * val / 255;
+  if (requested_level_limited == drv->current_level) {
+    return drv->current_level;
+  }
+
+  // New backlight level
+  drv->current_level = requested_level_limited;
+
+  int set_step = MAX_STEPS * drv->current_level / BACKLIGHT_MAX_LEVEL;
 
   if (set_step == 0) {
     backlight_shutdown();
@@ -252,6 +274,28 @@ int backlight_get(void) {
   return drv->current_level;
 }
 
+// Set maximal backlight level
+int backlight_set_max_level(int max_level) {
+  backlight_driver_t *drv = &g_backlight_driver;
+
+  if (!drv->initialized) {
+    return 0;
+  }
+
+  if (max_level < BACKLIGHT_MIN_LEVEL) {
+    max_level = BACKLIGHT_MIN_LEVEL;
+  }
+
+  if (max_level > BACKLIGHT_MAX_LEVEL) {
+    max_level = BACKLIGHT_MAX_LEVEL;
+  }
+
+  drv->max_level = max_level;
+  backlight_set(drv->requested_level);
+
+  return drv->current_level;
+}
+
 static void backlight_control_up(uint32_t *data, int steps) {
   for (int i = 0; i < steps; i++) {
     data[i] = TIM_PULSE(BACKLIGHT_CONTROL_T_UP_US);