diff --git a/bootloader/bootloader.c b/bootloader/bootloader.c
index abe532cab..2ec539f5f 100644
--- a/bootloader/bootloader.c
+++ b/bootloader/bootloader.c
@@ -67,27 +67,6 @@ void SysTick_Handler(void) {
 #endif
 }
 
-
-// ### from timer.c
-
-uint32_t timer_get_source_freq(uint32_t tim_id) {
-    uint32_t source;
-    if (tim_id == 1 || (8 <= tim_id && tim_id <= 11)) {
-        // TIM{1,8,9,10,11} are on APB2
-        source = HAL_RCC_GetPCLK2Freq();
-        if ((uint32_t)((RCC->CFGR & RCC_CFGR_PPRE2) >> 3) != RCC_HCLK_DIV1) {
-            source *= 2;
-        }
-    } else {
-        // TIM{2,3,4,5,6,7,12,13,14} are on APB1
-        source = HAL_RCC_GetPCLK1Freq();
-        if ((uint32_t)(RCC->CFGR & RCC_CFGR_PPRE1) != RCC_HCLK_DIV1) {
-            source *= 2;
-        }
-    }
-    return source;
-}
-
 // ###
 
 int main(void) {
diff --git a/extmod/modtrezorui/display-stmhal.h b/extmod/modtrezorui/display-stmhal.h
index 854130ff1..b9c0602b3 100644
--- a/extmod/modtrezorui/display-stmhal.h
+++ b/extmod/modtrezorui/display-stmhal.h
@@ -7,8 +7,6 @@
 
 #include STM32_HAL_H
 
-#define LED_PWM_TIM_PERIOD (10000)
-extern uint32_t timer_get_source_freq(uint32_t tim_id);
 
 #define DISPLAY_ILI9341V 0
 #define DISPLAY_ST7789V  1
@@ -20,6 +18,18 @@ void DATAS(const void *bytes, int len);
 
 static TIM_HandleTypeDef TIM1_Handle;
 
+#define LED_PWM_TIM_PERIOD (10000)
+
+static uint32_t timer1_get_source_freq() {
+    uint32_t source;
+    // TIM1 is on APB2
+    source = HAL_RCC_GetPCLK2Freq();
+    if ((uint32_t)((RCC->CFGR & RCC_CFGR_PPRE2) >> 3) != RCC_HCLK_DIV1) {
+        source *= 2;
+    }
+    return source;
+}
+
 void display_sram_init(void) {
     __GPIOE_CLK_ENABLE();
     __TIM1_CLK_ENABLE();
@@ -58,7 +68,7 @@ void display_sram_init(void) {
     // enable PWM timer
     TIM1_Handle.Instance = TIM1;
     TIM1_Handle.Init.Period = LED_PWM_TIM_PERIOD - 1;
-    TIM1_Handle.Init.Prescaler = timer_get_source_freq(1) / 1000000 - 1; // TIM runs at 1MHz
+    TIM1_Handle.Init.Prescaler = timer1_get_source_freq() / 1000000 - 1; // TIM runs at 1MHz
     TIM1_Handle.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
     TIM1_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
     TIM1_Handle.Init.RepetitionCounter = 0;