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uart.c fix from TMK (#7628)

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* uart.c fix from TMK

Backport from tmk/tmk_keyboard@c41e48a0ab

* Avoid deadlock when uart.c is usind in ISR

Backport from tmk/tmk_keyboard@55443fabb7
This commit is contained in:
Drashna Jaelre 2020-02-21 02:32:30 -08:00 committed by GitHub
parent 67ee050a0e
commit 1751c3cc25
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 44 additions and 10 deletions
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54
tmk_core/common/uart.c
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@ -31,9 +31,41 @@
#include "uart.h"
#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega168P__) || defined(__AVR_ATmega328P__)
# define UDRn UDR0
# define UBRRn UBRR0
# define UCSRnA UCSR0A
# define UCSRnB UCSR0B
# define UCSRnC UCSR0C
# define U2Xn U2X0
# define RXENn RXEN0
# define TXENn TXEN0
# define RXCIEn RXCIE0
# define UCSZn1 UCSZ01
# define UCSZn0 UCSZ00
# define UDRIEn UDRIE0
# define UDRE_vect USART_UDRE_vect
# define RX_vect USART_RX_vect
#elif defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega32U2__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__)
# define UDRn UDR1
# define UBRRn UBRR1
# define UCSRnA UCSR1A
# define UCSRnB UCSR1B
# define UCSRnC UCSR1C
# define U2Xn U2X1
# define RXENn RXEN1
# define TXENn TXEN1
# define RXCIEn RXCIE1
# define UCSZn1 UCSZ11
# define UCSZn0 UCSZ10
# define UDRIEn UDRIE1
# define UDRE_vect USART1_UDRE_vect
# define RX_vect USART1_RX_vect
#endif
// These buffers may be any size from 2 to 256 bytes.
#define RX_BUFFER_SIZE 64
#define TX_BUFFER_SIZE 40
#define TX_BUFFER_SIZE 256
static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
static volatile uint8_t tx_buffer_head;
@ -45,10 +77,10 @@ static volatile uint8_t rx_buffer_tail;
// Initialize the UART
void uart_init(uint32_t baud) {
cli();
UBRR0 = (F_CPU / 4 / baud - 1) / 2;
UCSR0A = (1 << U2X0);
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
UBRRn = (F_CPU / 4 / baud - 1) / 2;
UCSRnA = (1 << U2Xn);
UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
UCSRnC = (1 << UCSZn1) | (1 << UCSZn0);
tx_buffer_head = tx_buffer_tail = 0;
rx_buffer_head = rx_buffer_tail = 0;
sei();
@ -60,12 +92,14 @@ void uart_putchar(uint8_t c) {
i = tx_buffer_head + 1;
if (i >= TX_BUFFER_SIZE) i = 0;
// return immediately to avoid deadlock when interrupt is disabled(called from ISR)
if (tx_buffer_tail == i && (SREG & (1<<SREG_I)) == 0) return;
while (tx_buffer_tail == i)
; // wait until space in buffer
// cli();
tx_buffer[i] = c;
tx_buffer_head = i;
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0) | (1 << UDRIE0);
UCSRB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn) | (1 << UDRIEn);
// sei();
}
@ -95,12 +129,12 @@ uint8_t uart_available(void) {
}
// Transmit Interrupt
ISR(USART_UDRE_vect) {
ISR(UDRE_vect) {
uint8_t i;
if (tx_buffer_head == tx_buffer_tail) {
// buffer is empty, disable transmit interrupt
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
} else {
i = tx_buffer_tail + 1;
if (i >= TX_BUFFER_SIZE) i = 0;
@ -110,10 +144,10 @@ ISR(USART_UDRE_vect) {
}
// Receive Interrupt
ISR(USART_RX_vect) {
ISR(RX_vect) {
uint8_t c, i;
c = UDR0;
c = UDRn;
i = rx_buffer_head + 1;
if (i >= RX_BUFFER_SIZE) i = 0;
if (i != rx_buffer_tail) {