From 2a46759fe83a5295f7c06e2dab37c3f85848800e Mon Sep 17 00:00:00 2001
From: ennyKey <ennyKey@fn.de>
Date: Wed, 4 Dec 2024 22:33:17 +0100
Subject: [PATCH] stm32/uart: Enable UART FIFO for H7 MCUs.

The H7 has a hardware UART FIFO, so it's worth enabling it, to reduce the
chance of missed incoming characters.  Note that `HAL_UART_Init(&huart)`
does not activate the FIFO, it must be done explicitly by calling
`HAL_UARTEx_EnableFifoMode(&huart)`.

Signed-off-by: ennyKey <ennyKey@fn.de>
---
 ports/stm32/Makefile                         |  6 ++++++
 ports/stm32/boards/stm32h7xx_hal_conf_base.h |  1 +
 ports/stm32/uart.c                           | 11 ++++++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index 8ac9a8af03..eabbd64a3b 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -417,6 +417,12 @@ HAL_SRC_C += $(addprefix $(STM32LIB_HAL_BASE)/Src/stm32$(MCU_SERIES)xx_,\
 	)
 endif
 
+ifeq ($(MCU_SERIES),$(filter $(MCU_SERIES),h7))
+HAL_SRC_C += $(addprefix $(STM32LIB_HAL_BASE)/Src/stm32$(MCU_SERIES)xx_,\
+    hal_uart_ex.c \
+    )
+endif
+
 USBDEV_SRC_C += $(addprefix $(USBDEV_DIR)/,\
 	core/src/usbd_core.c \
 	core/src/usbd_ctlreq.c \
diff --git a/ports/stm32/boards/stm32h7xx_hal_conf_base.h b/ports/stm32/boards/stm32h7xx_hal_conf_base.h
index 670dee383f..1953ba020b 100644
--- a/ports/stm32/boards/stm32h7xx_hal_conf_base.h
+++ b/ports/stm32/boards/stm32h7xx_hal_conf_base.h
@@ -90,6 +90,7 @@
 #include "stm32h7xx_hal_spi.h"
 #include "stm32h7xx_hal_tim.h"
 #include "stm32h7xx_hal_uart.h"
+#include "stm32h7xx_hal_uart_ex.h"
 #include "stm32h7xx_hal_usart.h"
 #include "stm32h7xx_hal_wwdg.h"
 #include "stm32h7xx_ll_adc.h"
diff --git a/ports/stm32/uart.c b/ports/stm32/uart.c
index 91db91395e..55fa622142 100644
--- a/ports/stm32/uart.c
+++ b/ports/stm32/uart.c
@@ -653,7 +653,7 @@ bool uart_init(machine_uart_obj_t *uart_obj,
     huart.Init.HwFlowCtl = flow;
     huart.Init.OverSampling = UART_OVERSAMPLING_16;
 
-    #if defined(STM32G4)  // H7 and WB also have fifo..
+    #if defined(STM32G4) || defined(STM32H7) // WB also has a fifo..
     huart.FifoMode = UART_FIFOMODE_ENABLE;
     #endif
 
@@ -701,6 +701,12 @@ bool uart_init(machine_uart_obj_t *uart_obj,
         uart_obj->char_width = CHAR_WIDTH_8BIT;
     }
 
+    #if defined(STM32H7)
+    HAL_UARTEx_SetTxFifoThreshold(&huart, UART_TXFIFO_THRESHOLD_1_8);
+    HAL_UARTEx_SetRxFifoThreshold(&huart, UART_RXFIFO_THRESHOLD_1_8);
+    HAL_UARTEx_EnableFifoMode(&huart);
+    #endif
+
     uart_obj->mp_irq_trigger = 0;
     uart_obj->mp_irq_obj = NULL;
 
@@ -1141,6 +1147,9 @@ size_t uart_tx_data(machine_uart_obj_t *self, const void *src_in, size_t num_cha
     // timeout_char by FIFO size + 1.
     // STM32G4 has 8 words FIFO.
     timeout = (8 + 1) * self->timeout_char;
+    #elif defined(STM32H7)
+    // STM32H7 has 16 words FIFO.
+    timeout = (16 + 1) * self->timeout_char;
     #else
     // The timeout specified here is for waiting for the TX data register to
     // become empty (ie between chars), as well as for the final char to be