| Message ID | 1493144135-898-1-git-send-email-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
On 25/04/2017 20:15, Geert Uytterhoeven wrote: > 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> > --- > A big thanks to Richard! > I had no idea what was happening here, until I saw his patch passing by > in a stable backport. :) you're welcome ! > In v4.3 and older, the field is called sg_len_tx. > --- > drivers/tty/serial/sh-sci.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c > index 9a47cc4f16a2798f..a15739202d6c75f2 100644 > --- a/drivers/tty/serial/sh-sci.c > +++ b/drivers/tty/serial/sh-sci.c > @@ -1545,7 +1545,16 @@ static void sci_free_dma(struct uart_port *port) > 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) > { > } > @@ -1553,7 +1562,9 @@ static inline void sci_request_dma(struct uart_port *port) > 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) > { > @@ -2566,6 +2577,7 @@ static const 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, >
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 9a47cc4f16a2798f..a15739202d6c75f2 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1545,7 +1545,16 @@ static void sci_free_dma(struct uart_port *port) 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) { } @@ -1553,7 +1562,9 @@ static inline void sci_request_dma(struct uart_port *port) 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) { @@ -2566,6 +2577,7 @@ static const 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,
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> --- A big thanks to Richard! I had no idea what was happening here, until I saw his patch passing by in a stable backport. In v4.3 and older, the field is called sg_len_tx. --- drivers/tty/serial/sh-sci.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)