From c2b310ad866ad218993c78f3af02d6aa991a6773 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Thu, 8 Jul 2021 08:24:45 +1000
Subject: [PATCH] HAL_ChibiOS: implement NOFIFO option for uarts

---
 libraries/AP_HAL_ChibiOS/UARTDriver.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
index a7141908a8..5b70d66176 100644
--- a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
+++ b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
@@ -308,6 +308,16 @@ void UARTDriver::begin(uint32_t b, uint16_t rxS, uint16_t txS)
     }
 #endif
 
+#if defined(USART_CR1_FIFOEN)
+    // enable the UART FIFO on G4 and H7. This allows for much higher baudrates
+    // without data loss when not using DMA
+    if (_last_options & OPTION_NOFIFO) {
+        _cr1_options &= ~USART_CR1_FIFOEN;
+    } else {
+        _cr1_options |= USART_CR1_FIFOEN;
+    }
+#endif
+
     /*
       allocate the write buffer
      */