diff options
Diffstat (limited to '0116-serial-8250-Store-to-lsr_save_flags-after-lsr-read.patch')
| -rw-r--r-- | 0116-serial-8250-Store-to-lsr_save_flags-after-lsr-read.patch | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/0116-serial-8250-Store-to-lsr_save_flags-after-lsr-read.patch b/0116-serial-8250-Store-to-lsr_save_flags-after-lsr-read.patch new file mode 100644 index 000000000000..2f679e64923a --- /dev/null +++ b/0116-serial-8250-Store-to-lsr_save_flags-after-lsr-read.patch @@ -0,0 +1,46 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com> +Date: Fri, 20 May 2022 13:35:41 +0300 +Subject: [PATCH] serial: 8250: Store to lsr_save_flags after lsr read +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +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 <stable@kernel.org> +Acked-by: Uwe Kleine-König <u.kleine-koenig@penugtronix.de> +Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> +Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> +Link: https://lore.kernel.org/r/f4d774be-1437-a550-8334-19d8722ab98c@linux.intel.com +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + drivers/tty/serial/8250/8250_port.c | 2 ++ + 1 file changed, 2 insertions(+) + +diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c +index 1fbd5bf264bec9ed8c3f43f3f05b85641da0e163..7e295d2701b287180aa46675d0d8ccabf863fdf1 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 |