From: Ilpo Järvinen Date: Fri, 20 May 2022 10:35:41 +0000 (+0300) Subject: serial: 8250: Store to lsr_save_flags after lsr read X-Git-Tag: v5.15.73~2884 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9b5a3b16c4aa35f1ce3a4ee5dcfbd22e1b6b2a7a;p=platform%2Fkernel%2Flinux-rpi.git serial: 8250: Store to lsr_save_flags after lsr read commit be03b0651ffd8bab69dfd574c6818b446c0753ce upstream. Not all LSR register flags are preserved across reads. Therefore, LSR readers must store the non-preserved bits into lsr_save_flags. This fix was initially mixed into feature commit f6f586102add ("serial: 8250: Handle UART without interrupt on TEMT using em485"). However, that feature change had a flaw and it was reverted to make room for simpler approach providing the same feature. The embedded fix got reverted with the feature change. Re-add the lsr_save_flags fix and properly mark it's a fix. Link: https://lore.kernel.org/all/1d6c31d-d194-9e6a-ddf9-5f29af829f3@linux.intel.com/T/#m1737eef986bd20cf19593e344cebd7b0244945fc Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250") Cc: stable Acked-by: Uwe Kleine-König Signed-off-by: Uwe Kleine-König Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/f4d774be-1437-a550-8334-19d8722ab98c@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 2285ef9..df9731f 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1535,6 +1535,8 @@ static inline void __stop_tx(struct uart_8250_port *p) if (em485) { unsigned char lsr = serial_in(p, UART_LSR); + p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS; + /* * To provide required timeing and allow FIFO transfer, * __stop_tx_rs485() must be called only when both FIFO and