From b98946b5c1b46e9399dae8d1cc41a15b2a5ee15f Mon Sep 17 00:00:00 2001
From: Victor Oliveira <rhapsodyv@gmail.com>
Date: Thu, 10 Sep 2020 00:46:50 -0300
Subject: [PATCH] Raise STM32F1 UART IRQ Priority, add error handling (#19301)

(Error handling for Overrun, Framing and Parity.)
---
 Marlin/src/HAL/STM32/MarlinSerial.cpp   |  6 +--
 Marlin/src/HAL/STM32F1/MarlinSerial.cpp | 55 ++++++++++++++++---------
 Marlin/src/HAL/STM32F1/MarlinSerial.h   | 15 +++++++
 3 files changed, 52 insertions(+), 24 deletions(-)

diff --git a/Marlin/src/HAL/STM32/MarlinSerial.cpp b/Marlin/src/HAL/STM32/MarlinSerial.cpp
index 8d99ab7855..2d799ea54d 100644
--- a/Marlin/src/HAL/STM32/MarlinSerial.cpp
+++ b/Marlin/src/HAL/STM32/MarlinSerial.cpp
@@ -55,10 +55,8 @@
 
 void MarlinSerial::begin(unsigned long baud, uint8_t config) {
   HardwareSerial::begin(baud, config);
-  // replace the IRQ callback with the one we have defined
-  #if ENABLED(EMERGENCY_PARSER)
-    _serial.rx_callback = _rx_callback;
-  #endif
+  // Replace the IRQ callback with the one we have defined
+  TERN_(EMERGENCY_PARSER, _serial.rx_callback = _rx_callback);
 }
 
 // This function is Copyright (c) 2006 Nicholas Zambetti.
diff --git a/Marlin/src/HAL/STM32F1/MarlinSerial.cpp b/Marlin/src/HAL/STM32F1/MarlinSerial.cpp
index 61fde718b3..9a48e901f4 100644
--- a/Marlin/src/HAL/STM32F1/MarlinSerial.cpp
+++ b/Marlin/src/HAL/STM32F1/MarlinSerial.cpp
@@ -29,28 +29,43 @@
 // Copied from ~/.platformio/packages/framework-arduinoststm32-maple/STM32F1/system/libmaple/usart_private.h
 // Changed to handle Emergency Parser
 static inline __always_inline void my_usart_irq(ring_buffer *rb, ring_buffer *wb, usart_reg_map *regs, MarlinSerial &serial) {
-   /* Handle RXNEIE and TXEIE interrupts.
-    * RXNE signifies availability of a byte in DR.
-    *
-    * See table 198 (sec 27.4, p809) in STM document RM0008 rev 15.
-    * We enable RXNEIE.
-    */
-  if ((regs->CR1 & USART_CR1_RXNEIE) && (regs->SR & USART_SR_RXNE)) {
-    uint8_t c = (uint8)regs->DR;
-    #ifdef USART_SAFE_INSERT
-      // If the buffer is full and the user defines USART_SAFE_INSERT,
-      // ignore new bytes.
-      rb_safe_insert(rb, c);
-    #else
-      // By default, push bytes around in the ring buffer.
-      rb_push_insert(rb, c);
-    #endif
-    #if ENABLED(EMERGENCY_PARSER)
-      emergency_parser.update(serial.emergency_state, c);
-    #endif
+ /* Handle RXNEIE and TXEIE interrupts.
+  * RXNE signifies availability of a byte in DR.
+  *
+  * See table 198 (sec 27.4, p809) in STM document RM0008 rev 15.
+  * We enable RXNEIE.
+  */
+  uint32_t srflags = regs->SR, cr1its = regs->CR1;
+
+  if ((cr1its & USART_CR1_RXNEIE) && (srflags & USART_SR_RXNE)) {
+    if (srflags & USART_SR_FE || srflags & USART_SR_PE ) {
+      // framing error or parity error
+      regs->DR; // Read and throw away the data, which also clears FE and PE
+    }
+    else {
+      uint8_t c = (uint8)regs->DR;
+      #ifdef USART_SAFE_INSERT
+        // If the buffer is full and the user defines USART_SAFE_INSERT,
+        // ignore new bytes.
+        rb_safe_insert(rb, c);
+      #else
+        // By default, push bytes around in the ring buffer.
+        rb_push_insert(rb, c);
+      #endif
+      #if ENABLED(EMERGENCY_PARSER)
+        emergency_parser.update(serial.emergency_state, c);
+      #endif
+    }
+  }
+  else if (srflags & USART_SR_ORE) {
+    // overrun and empty data, just do a dummy read to clear ORE
+    // and prevent a raise condition where a continous interrupt stream (due to ORE set) occurs
+    // (see chapter "Overrun error" ) in STM32 reference manual
+    regs->DR;
   }
+
   // TXE signifies readiness to send a byte to DR.
-  if ((regs->CR1 & USART_CR1_TXEIE) && (regs->SR & USART_SR_TXE)) {
+  if ((cr1its & USART_CR1_TXEIE) && (srflags & USART_SR_TXE)) {
     if (!rb_is_empty(wb))
       regs->DR=rb_remove(wb);
     else
diff --git a/Marlin/src/HAL/STM32F1/MarlinSerial.h b/Marlin/src/HAL/STM32F1/MarlinSerial.h
index 4e8a47d2f9..eb0059bfbc 100644
--- a/Marlin/src/HAL/STM32F1/MarlinSerial.h
+++ b/Marlin/src/HAL/STM32F1/MarlinSerial.h
@@ -22,6 +22,7 @@
 #pragma once
 
 #include <HardwareSerial.h>
+#include <libmaple/usart.h>
 #include <WString.h>
 
 #include "../../inc/MarlinConfigPre.h"
@@ -29,6 +30,8 @@
   #include "../../feature/e_parser.h"
 #endif
 
+#define UART_IRQ_PRIO 1
+
 class MarlinSerial : public HardwareSerial {
 public:
   MarlinSerial(struct usart_dev *usart_device, uint8 tx_pin, uint8 rx_pin) :
@@ -38,6 +41,18 @@ public:
     #endif
     { }
 
+  #ifdef UART_IRQ_PRIO
+    // shadow the parent methods to set irq priority after the begin
+    void begin(uint32 baud) {
+      MarlinSerial::begin(baud, SERIAL_8N1);
+    }
+
+    void begin(uint32 baud, uint8_t config) {
+      HardwareSerial::begin(baud, config);
+      nvic_irq_set_priority(c_dev()->irq_num, UART_IRQ_PRIO);
+    }
+  #endif
+
   #if ENABLED(EMERGENCY_PARSER)
     EmergencyParser::State emergency_state;
   #endif