boards: st: stm32h7s78_dk: enable MEMC & SMH for display

In case of DISPLAY is enabled, ensure that MEMC as well as
Shared-Multi-Heap is enabled in order to use for framebuffer.
Moreover, since PSRAM is 32MB large, HEAP size should be set
AUTO instead of SMALL which is the default since SRAM is rather
small.

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

Author: Alain Volmat

boards/st/stm32h7s78_dk/Kconfig.defconfig

@@ -14,4 +14,21 @@ config NET_L2_ETHERNET
 
 endif # NETWORKING
 
+if DISPLAY
+# MEMC needs to be enabled in order to store
+# display frame buffer to external PSRAM
+config MEMC
+	default y
+
+# Rely on Multi-Heap / Shared-Multi-Heap for PSRAM access
+config MULTI_HEAP
+	default y
+config SHARED_MULTI_HEAP
+	default y
+
+# Let LTDC use memory allocated via SMH
+config STM32_LTDC_FB_USE_SHARED_MULTI_HEAP
+	default y
+endif # DISPLAY
+
 endif # BOARD_STM32H7S78_DK

boards/st/stm32h7s78_dk/stm32h7s78_dk_defconfig

@@ -18,3 +18,10 @@ CONFIG_UART_CONSOLE=y
 
 # enable GPIO
 CONFIG_GPIO=y
+
+# SRAM0 being small (128KB), SYS_HEAP_SMALL_ONLY
+# is automatically selected, leading to not being
+# able to tackle HEAP on the large PSRAM. Force it
+# to AUTO in order to be able to handle HEAP on
+# both SRAM and PSRAM
+CONFIG_SYS_HEAP_AUTO=y