From 0a8faa83d992ba88375913d0ed7957e47ef7f74a Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Fri, 29 Dec 2023 07:27:02 +1100
Subject: [PATCH] HAL_ChibiOS: allow for up to 12.5MBps on H7 UARTs

use 8x oversampling instead of 16x oversampling
---
 libraries/AP_HAL_ChibiOS/UARTDriver.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
index 6593dffe7e..a04537fdbd 100644
--- a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
+++ b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
@@ -430,6 +430,18 @@ void UARTDriver::_begin(uint32_t b, uint16_t rxS, uint16_t txS)
             sercfg.cr2 = _cr2_options;
             sercfg.cr3 = _cr3_options;
 
+#if defined(STM32H7)
+            /*
+              H7 defaults to 16x oversampling. To get the highest
+              possible baudrates we need to drop back to 8x
+              oversampling. The H7 UART clock is 100MHz. This allows
+              for up to 12.5MBps on H7 UARTs
+             */
+            if (_baudrate > 100000000UL / 16U) {
+                sercfg.cr1 |= USART_CR1_OVER8;
+            }
+#endif
+
 #ifndef HAL_UART_NODMA
             if (rx_dma_enabled) {
                 sercfg.cr1 |= USART_CR1_IDLEIE;