+ Felipe
On Mon, Jul 8, 2013 at 3:04 AM, Alexander Savchenko
<oleksandr.savchenko@xxxxxx> wrote:
> From: Dmitry Fink <finik@xxxxxx>
>
> Current logic results in interrupt storm since the fifo
> is constantly below the threshold level. Change the logic
> to fill all the available spaces in the fifo as long as
> we have data to minimize the possibilty of underflow and
> elimiate excessive interrupts.
>
> Signed-off-by: Dmitry Fink <finik@xxxxxx>
> Signed-off-by: Alexander Savchenko <oleksandr.savchenko@xxxxxx>
Hmm, another OMAP serial patch that wasn't Cc'd to linux-omap where
OMAP users might have seen it. :(
I just bisected a strange problem in linux-next on OMAP3 down to this
patch. Reverting it fixes the problem.
On OMAP3530 Beagle and Overo, after boot, doing a 'cat /proc/cpuinfo'
was not returning to a prompt, suggesting something strange with the
FIFO. Hitting return gets me back to a prompt.
Greg, this one should also be dropped from tty-next until it can be
further investgated and the problem solved.
Thanks,
Kevin
> ---
> drivers/tty/serial/omap-serial.c | 3 ++-
> include/uapi/linux/serial_reg.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index b6d1728..5c9b074 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -310,7 +310,8 @@ static void transmit_chars(struct uart_omap_port *up, unsigned int lsr)
> serial_omap_stop_tx(&up->port);
> return;
> }
> - count = up->port.fifosize / 4;
> + count = up->port.fifosize -
> + (serial_in(up, UART_OMAP_TXFIFO_LVL) & 0xFF);
> do {
> serial_out(up, UART_TX, xmit->buf[xmit->tail]);
> xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h
> index e632260..97c26be 100644
> --- a/include/uapi/linux/serial_reg.h
> +++ b/include/uapi/linux/serial_reg.h
> @@ -366,6 +366,7 @@
> #define UART_OMAP_MDR1_FIR_MODE 0x05 /* FIR mode */
> #define UART_OMAP_MDR1_CIR_MODE 0x06 /* CIR mode */
> #define UART_OMAP_MDR1_DISABLE 0x07 /* Disable (default state) */
> +#define UART_OMAP_TXFIFO_LVL 0x1A /* TX FIFO fullness */
>
> /*
> * These are definitions for the Exar XR17V35X and XR17(C|D)15X
> --
> 1.7.9.5
>
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