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Subject[PATCH 2/7] serial: stm32: fix rx error handling
Date
- Fixes parity and framing error bit by clearing parity and framing error
flag. The current implementation doesn't clear the error bits when an
error is detected.
- Fixes the incorrect name of framing error clearing flag in header file.
- Fixes misalignement between data frame and errors status. The status
read for "n" frame was the status of "n+1" frame".
- Fixes break detection was not triggered by the expected register.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")
Signed-off-by: Erwan Le Ray <erwan.leray@st.com>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index e832185..f6b7393 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -225,35 +225,51 @@ static void stm32_receive_chars(struct uart_port *port, bool threaded)

while (stm32_pending_rx(port, &sr, &stm32_port->last_res, threaded)) {
sr |= USART_SR_DUMMY_RX;
- c = stm32_get_char(port, &sr, &stm32_port->last_res);
flag = TTY_NORMAL;
- port->icount.rx++;

+ /*
+ * Status bits has to be cleared before reading the RDR:
+ * In FIFO mode, reading the RDR will pop the next data
+ * (if any) along with its status bits into the SR.
+ * Not doing so leads to misalignement between RDR and SR,
+ * and clear status bits of the next rx data.
+ *
+ * Clear errors flags for stm32f7 and stm32h7 compatible
+ * devices. On stm32f4 compatible devices, the error bit is
+ * cleared by the sequence [read SR - read DR].
+ */
+ if ((sr & USART_SR_ERR_MASK) && ofs->icr != UNDEF_REG)
+ stm32_clr_bits(port, ofs->icr, USART_ICR_ORECF |
+ USART_ICR_PECF | USART_ICR_FECF);
+
+ c = stm32_get_char(port, &sr, &stm32_port->last_res);
+ port->icount.rx++;
if (sr & USART_SR_ERR_MASK) {
- if (sr & USART_SR_LBD) {
- port->icount.brk++;
- if (uart_handle_break(port))
- continue;
- } else if (sr & USART_SR_ORE) {
- if (ofs->icr != UNDEF_REG)
- writel_relaxed(USART_ICR_ORECF,
- port->membase +
- ofs->icr);
+ if (sr & USART_SR_ORE) {
port->icount.overrun++;
} else if (sr & USART_SR_PE) {
port->icount.parity++;
} else if (sr & USART_SR_FE) {
- port->icount.frame++;
+ /* Break detection if character is null */
+ if (!c) {
+ port->icount.brk++;
+ if (uart_handle_break(port))
+ continue;
+ } else {
+ port->icount.frame++;
+ }
}

sr &= port->read_status_mask;

- if (sr & USART_SR_LBD)
- flag = TTY_BREAK;
- else if (sr & USART_SR_PE)
+ if (sr & USART_SR_PE) {
flag = TTY_PARITY;
- else if (sr & USART_SR_FE)
- flag = TTY_FRAME;
+ } else if (sr & USART_SR_FE) {
+ if (!c)
+ flag = TTY_BREAK;
+ else
+ flag = TTY_FRAME;
+ }
}

if (uart_handle_sysrq_char(port, c))
@@ -721,14 +737,14 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
if (termios->c_iflag & INPCK)
port->read_status_mask |= USART_SR_PE | USART_SR_FE;
if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
- port->read_status_mask |= USART_SR_LBD;
+ port->read_status_mask |= USART_SR_FE;

/* Characters to ignore */
port->ignore_status_mask = 0;
if (termios->c_iflag & IGNPAR)
port->ignore_status_mask = USART_SR_PE | USART_SR_FE;
if (termios->c_iflag & IGNBRK) {
- port->ignore_status_mask |= USART_SR_LBD;
+ port->ignore_status_mask |= USART_SR_FE;
/*
* If we're ignoring parity and break indicators,
* ignore overruns too (for real raw support).
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index a70aa50..8d34802 100644
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -108,7 +108,6 @@ struct stm32_usart_info stm32h7_info = {
#define USART_SR_RXNE BIT(5)
#define USART_SR_TC BIT(6)
#define USART_SR_TXE BIT(7)
-#define USART_SR_LBD BIT(8)
#define USART_SR_CTSIF BIT(9)
#define USART_SR_CTS BIT(10) /* F7 */
#define USART_SR_RTOF BIT(11) /* F7 */
@@ -120,8 +119,7 @@ struct stm32_usart_info stm32h7_info = {
#define USART_SR_SBKF BIT(18) /* F7 */
#define USART_SR_WUF BIT(20) /* H7 */
#define USART_SR_TEACK BIT(21) /* F7 */
-#define USART_SR_ERR_MASK (USART_SR_LBD | USART_SR_ORE | \
- USART_SR_FE | USART_SR_PE)
+#define USART_SR_ERR_MASK (USART_SR_ORE | USART_SR_FE | USART_SR_PE)
/* Dummy bits */
#define USART_SR_DUMMY_RX BIT(16)

@@ -168,8 +166,6 @@ struct stm32_usart_info stm32h7_info = {
/* USART_CR2 */
#define USART_CR2_ADD_MASK GENMASK(3, 0) /* F4 */
#define USART_CR2_ADDM7 BIT(4) /* F7 */
-#define USART_CR2_LBDL BIT(5)
-#define USART_CR2_LBDIE BIT(6)
#define USART_CR2_LBCL BIT(8)
#define USART_CR2_CPHA BIT(9)
#define USART_CR2_CPOL BIT(10)
@@ -226,12 +222,10 @@ struct stm32_usart_info stm32h7_info = {

/* USART_ICR */
#define USART_ICR_PECF BIT(0) /* F7 */
-#define USART_ICR_FFECF BIT(1) /* F7 */
-#define USART_ICR_NCF BIT(2) /* F7 */
+#define USART_ICR_FECF BIT(1) /* F7 */
#define USART_ICR_ORECF BIT(3) /* F7 */
#define USART_ICR_IDLECF BIT(4) /* F7 */
#define USART_ICR_TCCF BIT(6) /* F7 */
-#define USART_ICR_LBDCF BIT(8) /* F7 */
#define USART_ICR_CTSCF BIT(9) /* F7 */
#define USART_ICR_RTOCF BIT(11) /* F7 */
#define USART_ICR_EOBCF BIT(12) /* F7 */
--
1.9.1
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