5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sherry Sun <sherry.sun@xxxxxxx>
commit 282069845af388b08d622ad192b831dcd0549c62 upstream.
Do not read the data register to clear the error flags for lpuart32
platforms, the additional read may cause the receive FIFO underflow
since the DMA has already read the data register.
Actually all lpuart32 platforms support write 1 to clear those error
bits, let's use this method to better clear the error flags.
Fixes: 42b68768e51b ("serial: fsl_lpuart: DMA support for 32-bit variant")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
Link: https://lore.kernel.org/r/20230801022304.24251-1-sherry.sun@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1023,8 +1023,8 @@ static void lpuart_copy_rx_to_tty(struct
unsigned long sr = lpuart32_read(&sport->port, UARTSTAT);
if (sr & (UARTSTAT_PE | UARTSTAT_FE)) {
- /* Read DR to clear the error flags */
- lpuart32_read(&sport->port, UARTDATA);
+ /* Clear the error flags */
+ lpuart32_write(&sport->port, sr, UARTSTAT);
if (sr & UARTSTAT_PE)
sport->port.icount.parity++;
