lkml.org 
[lkml]   [2022]   [Jun]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 1/6] serial: 8250: Store to lsr_save_flags after lsr read
Date
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.

Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
Link: https://lore.kernel.org/all/1d6c31d-d194-9e6a-ddf9-5f29af829f3@linux.intel.com/T/#m1737eef986bd20cf19593e344cebd7b0244945fc
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@penugtronix.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
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 4998799abae2..c5e0f925f4b6 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1511,6 +1511,8 @@ static inline void __stop_tx(struct uart_8250_port *p)
unsigned char lsr = serial_in(p, UART_LSR);
u64 stop_delay = 0;

+ p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+
if (!(lsr & UART_LSR_THRE))
return;
/*
--
2.30.2
\
 
 \ /
  Last update: 2022-06-06 15:13    [W:0.159 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site