4.4-stable review patch. If anyone has any objections, please let me know.
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From: Geert Uytterhoeven geert+renesas@glider.be
[ Upstream commit 1cf4a7efdc71cab84c42cfea7200608711ea954f ]
If DMA is enabled and used, a burst of old data may be seen on the serial console during "poweroff" or "reboot". uart_flush_buffer() clears the circular buffer, but sci_port.tx_dma_len is not reset. This leads to a circular buffer overflow, dumping (UART_XMIT_SIZE - sci_port.tx_dma_len) bytes.
To fix this, add a .flush_buffer() callback that resets sci_port.tx_dma_len.
Inspired by commit 31ca2c63fdc0aee7 ("tty/serial: atmel: fix race condition (TX+DMA)").
Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/sh-sci.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1457,7 +1457,16 @@ static void sci_free_dma(struct uart_por if (s->chan_rx) sci_rx_dma_release(s, false); } -#else + +static void sci_flush_buffer(struct uart_port *port) +{ + /* + * In uart_flush_buffer(), the xmit circular buffer has just been + * cleared, so we have to reset tx_dma_len accordingly. + */ + to_sci_port(port)->tx_dma_len = 0; +} +#else /* !CONFIG_SERIAL_SH_SCI_DMA */ static inline void sci_request_dma(struct uart_port *port) { } @@ -1465,7 +1474,9 @@ static inline void sci_request_dma(struc static inline void sci_free_dma(struct uart_port *port) { } -#endif + +#define sci_flush_buffer NULL +#endif /* !CONFIG_SERIAL_SH_SCI_DMA */
static irqreturn_t sci_rx_interrupt(int irq, void *ptr) { @@ -2205,6 +2216,7 @@ static struct uart_ops sci_uart_ops = { .break_ctl = sci_break_ctl, .startup = sci_startup, .shutdown = sci_shutdown, + .flush_buffer = sci_flush_buffer, .set_termios = sci_set_termios, .pm = sci_pm, .type = sci_type,