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| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2022-05-20 13:35:41 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-06-25 12:46:44 +0300 |
| commit | 2bdcf89a2d6bd638b3ab0e16603034587c541938 (patch) | |
| tree | e6e183695c23391088487f61b1b7630beda1750d /drivers | |
| parent | 0ef6917c0524da5b88496b9706628ffef108b9bb (diff) | |
| download | linux-2bdcf89a2d6bd638b3ab0e16603034587c541938.tar.xz | |
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 <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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/tty/serial/8250/8250_port.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index bbfcb220e1eb..1aca30a3f716 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1524,6 +1524,8 @@ 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 |