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authorIlpo Järvinen <ilpo.jarvinen@linux.intel.com>2022-03-14 12:14:32 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-04-08 15:23:50 +0300
commit16e3238047322c3967e601b2813a10837fb2acb9 (patch)
tree868cbfd180bb86b7977caac412fbbf669dedff8f /include
parenta885e17cf5f2dd6606abe825a001fd09a5c29c2e (diff)
downloadlinux-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.h2
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)