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 /drivers/tty | |
| 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 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/8250/8250_dma.c | 11 | ||||
| -rw-r--r-- | drivers/tty/serial/8250/8250_port.c | 4 | ||||
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 14 |
3 files changed, 25 insertions, 4 deletions
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 890fa7ddaa7f..b3c3f7e5851a 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -64,10 +64,19 @@ int serial8250_tx_dma(struct uart_8250_port *p) struct uart_8250_dma *dma = p->dma; struct circ_buf *xmit = &p->port.state->xmit; struct dma_async_tx_descriptor *desc; + struct uart_port *up = &p->port; int ret; - if (dma->tx_running) + if (dma->tx_running) { + if (up->x_char) { + dmaengine_pause(dma->txchan); + uart_xchar_out(up, UART_TX); + dmaengine_resume(dma->txchan); + } return 0; + } else if (up->x_char) { + uart_xchar_out(up, UART_TX); + } if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) { /* We have been called from __dma_tx_complete() */ diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 868ccb3e16cf..723ec0806799 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1819,9 +1819,7 @@ void serial8250_tx_chars(struct uart_8250_port *up) int count; if (port->x_char) { - serial_out(up, UART_TX, port->x_char); - port->icount.tx++; - port->x_char = 0; + uart_xchar_out(port, UART_TX); return; } if (uart_tx_stopped(port)) { diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index dc6129ddef85..eb15423f935a 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -653,6 +653,20 @@ static void uart_flush_buffer(struct tty_struct *tty) } /* + * This function performs low-level write of high-priority XON/XOFF + * character and accounting for it. + * + * Requires uart_port to implement .serial_out(). + */ +void uart_xchar_out(struct uart_port *uport, int offset) +{ + serial_port_out(uport, offset, uport->x_char); + uport->icount.tx++; + uport->x_char = 0; +} +EXPORT_SYMBOL_GPL(uart_xchar_out); + +/* * This function is used to send a high-priority XON/XOFF character to * the device */ |