display: stm32: ltdc: add SMH buffer alignment config option

Add the CONFIG_STM32_LTDC_FB_SMH_ALIGN option in order to
indicate the alignment required for the buffer allocated via
SMH.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>

drivers/display/Kconfig.stm32_ltdc

@@ -67,6 +67,11 @@ config STM32_LTDC_FB_SMH_ATTRIBUTE
 	  1: SMH_REG_ATTR_NON_CACHEABLE
 	  2: SMH_REG_ATTR_EXTERNAL
 
+config STM32_LTDC_FB_SMH_ALIGN
+	int "Shared multi heap buffer alignment for the display buffer"
+	depends on STM32_LTDC_FB_USE_SHARED_MULTI_HEAP
+	default 32
+
 config STM32_LTDC_DISABLE_FMC_BANK1
 	bool "Disable FMC bank1 for STM32F7/H7 series"
 	depends on SOC_SERIES_STM32H7X || SOC_SERIES_STM32F7X

drivers/display/display_stm32_ltdc.c

@@ -445,7 +445,7 @@ static int stm32_ltdc_init(const struct device *dev)
 #if defined(CONFIG_STM32_LTDC_FB_USE_SHARED_MULTI_HEAP)
 	data->frame_buffer = shared_multi_heap_aligned_alloc(
 			CONFIG_STM32_LTDC_FB_SMH_ATTRIBUTE,
-			32,
+			CONFIG_STM32_LTDC_FB_SMH_ALIGN,
 			CONFIG_STM32_LTDC_FB_NUM * data->frame_buffer_len);
 
 	if (data->frame_buffer == NULL) {