[PATCH v2 6/9] ARM: stm32: add STM32H7R7 platform support

Enable STM32H7R7 in the STM32 machine selection and compatible table.
Add low-level UART4 debug output using the register layout shared by
the STM32F7 and STM32H7 USART block.

Signed-off-by: Liu Changjie <[email protected]>
---
Changes in v2:
- Expand the MACH_STM32H7R7 help text to mention noMMU operation and
  execution from external memory.

 arch/arm/Kconfig.debug         | 12 ++++++++++++
 arch/arm/include/debug/stm32.S |  2 +-
 arch/arm/mach-stm32/Kconfig    |  9 +++++++++
 arch/arm/mach-stm32/board-dt.c |  1 +
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 366f162e1..e76750d9e 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -1202,6 +1202,17 @@ choice
 
 		  If unsure, say N.
 
+	config STM32H7RS_DEBUG_UART
+		bool "Use STM32H7RS UART for low-level debug"
+		depends on MACH_STM32H7R7
+		select DEBUG_STM32_UART
+		help
+		  Say Y here if you want kernel low-level debugging support on
+		  STM32H7RS platforms. The ART-Pi2 debug console is UART4 at
+		  physical address 0x40004c00.
+
+		  If unsure, say N.
+
 	config STM32MP1_DEBUG_UART
 		bool "Use STM32MP1 UART for low-level debug"
 		depends on MACH_STM32MP157
@@ -1582,6 +1593,7 @@ config DEBUG_UART_PHYS
 	default 0x20201000 if DEBUG_BCM2835
 	default 0x3e000000 if DEBUG_BCM_KONA_UART
 	default 0x3f201000 if DEBUG_BCM2836
+	default 0x40004c00 if STM32H7RS_DEBUG_UART
 	default 0x40010000 if STM32MP1_DEBUG_UART
 	default 0x40011000 if STM32F4_DEBUG_UART || STM32F7_DEBUG_UART || \
 				STM32H7_DEBUG_UART
diff --git a/arch/arm/include/debug/stm32.S b/arch/arm/include/debug/stm32.S
index b6d9df30e..2a8c25ede 100644
--- a/arch/arm/include/debug/stm32.S
+++ b/arch/arm/include/debug/stm32.S
@@ -10,7 +10,7 @@
 #endif
 
 #if defined(CONFIG_STM32F7_DEBUG_UART) || defined(CONFIG_STM32H7_DEBUG_UART) || \
-	defined(CONFIG_STM32MP1_DEBUG_UART)
+	defined(CONFIG_STM32H7RS_DEBUG_UART) || defined(CONFIG_STM32MP1_DEBUG_UART)
 #define STM32_USART_SR_OFF		0x1C
 #define STM32_USART_TDR_OFF		0x28
 #endif
diff --git a/arch/arm/mach-stm32/Kconfig b/arch/arm/mach-stm32/Kconfig
index 630b992f3..7bc52fe5a 100644
--- a/arch/arm/mach-stm32/Kconfig
+++ b/arch/arm/mach-stm32/Kconfig
@@ -40,6 +40,15 @@ config MACH_STM32H743
 	bool "STMicroelectronics STM32H743"
 	default y
 
+config MACH_STM32H7R7
+	bool "STMicroelectronics STM32H7R7"
+	default y
+	help
+	  Support for STMicroelectronics STM32H7R7 Cortex-M7
+	  microcontrollers. This enables support for boards based on the
+	  STM32H7R7 SoC, such as the RT-Thread ART-Pi2. These devices run
+	  Linux without an MMU and may execute from external memory.
+
 endif # ARMv7-M
 
 if ARCH_MULTI_V7
diff --git a/arch/arm/mach-stm32/board-dt.c b/arch/arm/mach-stm32/board-dt.c
index e6233c872..d1207b84a 100644
--- a/arch/arm/mach-stm32/board-dt.c
+++ b/arch/arm/mach-stm32/board-dt.c
@@ -19,6 +19,7 @@ static const char *const stm32_compat[] __initconst = {
 	"st,stm32h743",
 	"st,stm32h747",
 	"st,stm32h750",
+	"st,stm32h7r7",
 	"st,stm32mp131",
 	"st,stm32mp133",
 	"st,stm32mp135",
-- 
2.55.0