ARM: debug: stm32: add UART early console support for STM32H7

Add support of early console for STM32H7. Default UART instance is USART1,
but other UART instances can be configured by setting physical and virtual
base addresses in menuconfig.
Signed-off-by: Erwan Le Ray <erwan.leray@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/Kconfig.debug

@@ -1223,6 +1223,18 @@ choice
 
 		  If unsure, say N.
 
+	config STM32H7_DEBUG_UART
+		bool "Use STM32H7 UART for low-level debug"
+		depends on MACH_STM32H743
+		select DEBUG_STM32_UART
+		help
+		  Say Y here if you want kernel low-level debugging support
+		  on STM32H7 based platforms, which default UART is wired on
+		  USART1, but another UART instance can be selected by modifying
+		  CONFIG_DEBUG_UART_PHYS.
+
+		  If unsure, say N.
+
 	config TEGRA_DEBUG_UART_AUTO_ODMDATA
 		bool "Kernel low-level debugging messages via Tegra UART via ODMDATA"
 		depends on ARCH_TEGRA
@@ -1621,7 +1633,8 @@ config DEBUG_UART_PHYS
 	default 0x3e000000 if DEBUG_BCM_KONA_UART
 	default 0x3f201000 if DEBUG_BCM2836
 	default 0x4000e400 if DEBUG_LL_UART_EFM32
-	default 0x40011000 if STM32F4_DEBUG_UART || STM32F7_DEBUG_UART
+	default 0x40011000 if STM32F4_DEBUG_UART || STM32F7_DEBUG_UART || \
+				STM32H7_DEBUG_UART
 	default 0x40028000 if DEBUG_AT91_SAMV7_USART1
 	default 0x40081000 if DEBUG_LPC18XX_UART0
 	default 0x40090000 if DEBUG_LPC32XX

arch/arm/include/debug/stm32.S

@@ -9,7 +9,7 @@
 #define STM32_USART_TDR_OFF		0x04
 #endif
 
-#ifdef CONFIG_STM32F7_DEBUG_UART
+#if defined(CONFIG_STM32F7_DEBUG_UART) || defined(CONFIG_STM32H7_DEBUG_UART)
 #define STM32_USART_SR_OFF		0x1C
 #define STM32_USART_TDR_OFF		0x28
 #endif