5.4-stable review patch. If anyone has any objections, please let me know.
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From: Sherry Sun sherry.sun@nxp.com
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@kernel.org Signed-off-by: Sherry Sun sherry.sun@nxp.com Link: https://lore.kernel.org/r/20230801022304.24251-1-sherry.sun@nxp.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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++;