diff options
| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2022-03-14 12:14:32 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-04-08 15:23:50 +0300 |
| commit | 16e3238047322c3967e601b2813a10837fb2acb9 (patch) | |
| tree | 868cbfd180bb86b7977caac412fbbf669dedff8f /include | |
| parent | a885e17cf5f2dd6606abe825a001fd09a5c29c2e (diff) | |
| download | linux-16e3238047322c3967e601b2813a10837fb2acb9.tar.xz | |
serial: 8250: fix XOFF/XON sending when DMA is used
[ Upstream commit f58c252e30cf74f68b0054293adc03b5923b9f0e ]
When 8250 UART is using DMA, x_char (XON/XOFF) is never sent
to the wire. After this change, x_char is injected correctly.
Create uart_xchar_out() helper for sending the x_char out and
accounting related to it. It seems that almost every driver
does these same steps with x_char. Except for 8250, however,
almost all currently lack .serial_out so they cannot immediately
take advantage of this new helper.
The downside of this patch is that it might reintroduce
the problems some devices faced with mixed DMA/non-DMA transfer
which caused revert f967fc8f165f (Revert "serial: 8250_dma:
don't bother DMA with small transfers"). However, the impact
should be limited to cases with XON/XOFF (that didn't work
with DMA capable devices to begin with so this problem is not
very likely to cause a major issue, if any at all).
Fixes: 9ee4b83e51f74 ("serial: 8250: Add support for dmaengine")
Reported-by: Gilles Buloz <gilles.buloz@kontron.com>
Tested-by: Gilles Buloz <gilles.buloz@kontron.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220314091432.4288-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/serial_core.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index c58cc142d23f..8c32935e1059 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -458,6 +458,8 @@ extern void uart_handle_cts_change(struct uart_port *uport, extern void uart_insert_char(struct uart_port *port, unsigned int status, unsigned int overrun, unsigned int ch, unsigned int flag); +void uart_xchar_out(struct uart_port *uport, int offset); + #ifdef CONFIG_MAGIC_SYSRQ_SERIAL #define SYSRQ_TIMEOUT (HZ * 5) |