feat(core): implementation of backlight brightness correction.

diff --git a/core/embed/io/backlight/inc/io/backlight.h b/core/embed/io/backlight/inc/io/backlight.h
index be4fb2a1..ff701d23 100644
--- a/core/embed/io/backlight/inc/io/backlight.h
+++ b/core/embed/io/backlight/inc/io/backlight.h
@@ -37,8 +37,10 @@ typedef enum {
 // is set to zero level. If the action is set to `BACKLIGHT_RETAIN`,
 // the backlight level is not changed (if possible).
 //
+// The `gamma_exp` parameter specifies the gamma_exp correction factor.
+//
 // Returns `true` if the initialization was successful.
-bool backlight_init(backlight_action_t action);
+bool backlight_init(backlight_action_t action, float gamma_exp);
 
 // Deinitialize the backlight driver
 //
diff --git a/core/embed/io/backlight/stm32/backlight_pin.c b/core/embed/io/backlight/stm32/backlight_pin.c
index b7bf73d1..e21dfecc 100644
--- a/core/embed/io/backlight/stm32/backlight_pin.c
+++ b/core/embed/io/backlight/stm32/backlight_pin.c
@@ -52,9 +52,11 @@ static void backlight_off(void) {
   HAL_GPIO_Init(BACKLIGHT_PIN_PORT, &GPIO_InitStructure);
 }
 
-bool backlight_init(backlight_action_t action) {
+bool backlight_init(backlight_action_t action, float gamma_exp) {
   backlight_driver_t *drv = &g_backlight_driver;
 
+  UNUSED(gamma_exp);
+
   if (drv->initialized) {
     return true;
   }
diff --git a/core/embed/io/backlight/stm32/tps61043.c b/core/embed/io/backlight/stm32/tps61043.c
index 148c30c2..365a7aab 100644
--- a/core/embed/io/backlight/stm32/tps61043.c
+++ b/core/embed/io/backlight/stm32/tps61043.c
@@ -45,9 +45,11 @@ static backlight_driver_t g_backlight_driver = {
     .initialized = false,
 };
 
-bool backlight_init(backlight_action_t action) {
+bool backlight_init(backlight_action_t action, float gamma_exp) {
   backlight_driver_t *drv = &g_backlight_driver;
 
+  UNUSED(gamma_exp);
+
   if (drv->initialized) {
     return true;
   }
diff --git a/core/embed/io/backlight/stm32u5/tps61062.c b/core/embed/io/backlight/stm32u5/tps61062.c
index f6f59917..7c008a9d 100644
--- a/core/embed/io/backlight/stm32u5/tps61062.c
+++ b/core/embed/io/backlight/stm32u5/tps61062.c
@@ -61,7 +61,6 @@
 
 // API level range 0-255 is mapped to DAC steps 0-31
 #define INPUT_OFFSET 1
-#define GAMMA_CORRECTION 2.2f
 #define USTEPS_PER_STEP DMA_BUF_LENGTH
 #define USTEPS_COUNT (MAX_STEPS * USTEPS_PER_STEP)
 
@@ -102,6 +101,9 @@ typedef struct {
   // Max backlight level
   uint8_t max_level;
 
+  // Gamma exponent
+  float gamma_exp;
+
   TIM_HandleTypeDef tim;
 
   DMA_HandleTypeDef dma;
@@ -128,21 +130,38 @@ static void backlight_deinit_ll(void);
 
 static void DMA_XferCpltCallback(DMA_HandleTypeDef *hdma);
 
-// Brightness level gamma correction - eq: OUT = ( ( (IN - k) / d ) ^ GAMMA) * q
+// Applies gamma correction to a brightness input value.
+//
+// eq: OUT = ( ( (IN - k) / d ) ^ GAMMA) * q
+//
+// Parameters:
+//   in        - Input brightness value (e.g., 0-255).
+//   in_offset - Minimum input value (k in the equation),
+//               below which input is clamped.
+//   in_max    - Maximum input value (d + k in the equation).
+//   gamma_exp - Gamma exponent (GAMMA in the equation).
+//   out_max   - Maximum output value (q in the equation).
+//
+// The transformation performed is:
+//   OUT = ( ( (max(IN, in_offset) - in_offset) / (in_max - in_offset) ) ^
+//         gamma_exp) * out_max
+//
+// This normalizes the input, applies gamma correction, and scales to the output
+// range.
 static inline uint32_t gamma_correction(uint8_t in, uint8_t in_offset,
-                                        uint8_t in_max, float gamma,
+                                        uint8_t in_max, float gamma_exp,
                                         uint32_t out_max) {
   float out;
 
   out = (float)(MAX(in, in_offset) - in_offset) /
         (in_max - in_offset);  // Input normalization to <0;1>
-  out = powf(out, gamma);      // Gamma correction
+  out = powf(out, gamma_exp);  // Gamma correction
   out = out * out_max;         // Output denormalization to <0;out_max>
 
   return (uint32_t)out;
 }
 
-bool backlight_init(backlight_action_t action) {
+bool backlight_init(backlight_action_t action, float gamma_exp) {
   backlight_driver_t *drv = &g_backlight_driver;
 
   if (drv->initialized) {
@@ -286,6 +305,9 @@ bool backlight_init(backlight_action_t action) {
   drv->max_level = BACKLIGHT_MAX_LEVEL;
   drv->requested_level = BACKLIGHT_MIN_LEVEL;
 
+  // Store gamma exponent
+  drv->gamma_exp = gamma_exp;
+
   drv->initialized = true;
 
   return true;
@@ -337,7 +359,7 @@ bool backlight_set(uint8_t val) {
   // Perform gamma correction of the requested level
   drv->requested_level_corrected =
       gamma_correction(drv->requested_level_limited, INPUT_OFFSET,
-                       BACKLIGHT_MAX_LEVEL, GAMMA_CORRECTION, USTEPS_COUNT);
+                       BACKLIGHT_MAX_LEVEL, drv->gamma_exp, USTEPS_COUNT);
 
   // Calculate the mapping of requested level to steps (quotient)
   drv->requested_step =
diff --git a/core/embed/io/display/ltdc_dsi/display_driver.c b/core/embed/io/display/ltdc_dsi/display_driver.c
index a37d7bd3..9b873089 100644
--- a/core/embed/io/display/ltdc_dsi/display_driver.c
+++ b/core/embed/io/display/ltdc_dsi/display_driver.c
@@ -353,7 +353,7 @@ bool display_init(display_content_mode_t mode) {
 #endif
 
 #ifdef USE_BACKLIGHT
-  backlight_init(BACKLIGHT_RESET);
+  backlight_init(BACKLIGHT_RESET, GAMMA_EXP);
 #endif
 
   uint32_t fb_addr = display_fb_init();
diff --git a/core/embed/io/display/ltdc_dsi/display_internal.h b/core/embed/io/display/ltdc_dsi/display_internal.h
index e5db3f4a..dc486899 100644
--- a/core/embed/io/display/ltdc_dsi/display_internal.h
+++ b/core/embed/io/display/ltdc_dsi/display_internal.h
@@ -33,6 +33,12 @@
 #include "panels/stm32u5a9j-dk/stm32u5a9j-dk.h"
 #endif
 
+#define GAMMA_EXP_DEFAULT 1.0f
+
+#ifndef GAMMA_EXP
+#define GAMMA_EXP GAMMA_EXP_DEFAULT
+#endif
+
 // Hardware requires physical frame buffer alignment
 #ifdef USE_TRUSTZONE
 #define PHYSICAL_FRAME_BUFFER_ALIGNMENT TZ_SRAM_ALIGNMENT
diff --git a/core/embed/io/display/ltdc_dsi/panels/lx250a2401a/lx250a2401a.h b/core/embed/io/display/ltdc_dsi/panels/lx250a2401a/lx250a2401a.h
index a32c03f4..9e36b0e5 100644
--- a/core/embed/io/display/ltdc_dsi/panels/lx250a2401a/lx250a2401a.h
+++ b/core/embed/io/display/ltdc_dsi/panels/lx250a2401a/lx250a2401a.h
@@ -45,6 +45,8 @@
 #define PANEL_DSI_LANES DSI_TWO_DATA_LANES
 #define PANEL_LTDC_PIXEL_FORMAT LTDC_PIXEL_FORMAT_ARGB8888
 
+#define GAMMA_EXP 2.2f
+
 // Size of the physical frame buffer in bytes
 //
 // It's smaller than size of the virtual frame buffer
diff --git a/core/embed/io/display/st-7789/display_driver.c b/core/embed/io/display/st-7789/display_driver.c
index 3e1e5179..fd4b4792 100644
--- a/core/embed/io/display/st-7789/display_driver.c
+++ b/core/embed/io/display/st-7789/display_driver.c
@@ -71,7 +71,7 @@ bool display_init(display_content_mode_t mode) {
     display_io_init_fmc();
     display_panel_init();
     display_panel_set_little_endian();
-    backlight_init(BACKLIGHT_RESET);
+    backlight_init(BACKLIGHT_RESET, GAMMA_EXP);
   } else {
     // Reinitialize FMC to set correct timing
     // We have to do this in reinit because boardloader is fixed.
@@ -80,7 +80,7 @@ bool display_init(display_content_mode_t mode) {
     // Important for model T as this is not set in boardloader
     display_panel_set_little_endian();
     display_panel_reinit();
-    backlight_init(BACKLIGHT_RETAIN);
+    backlight_init(BACKLIGHT_RETAIN, GAMMA_EXP);
   }
 
 #ifdef FRAMEBUFFER
diff --git a/core/embed/io/display/st-7789/display_internal.h b/core/embed/io/display/st-7789/display_internal.h
index b8e94455..929090a5 100644
--- a/core/embed/io/display/st-7789/display_internal.h
+++ b/core/embed/io/display/st-7789/display_internal.h
@@ -10,6 +10,12 @@
 
 #endif  // FRAMEBUFFER
 
+#define GAMMA_EXP_DEFAULT 1.0f
+
+#ifndef GAMMA_EXP
+#define GAMMA_EXP GAMMA_EXP_DEFAULT
+#endif
+
 // Display driver state
 typedef struct {
   // Set if the driver is initialized