On 04/07/2016 01:37 PM, Andy Shevchenko wrote:
> Intel Quark has 16550A compatible UART with autoflow feature enabled. It has
> only 16 bytes of FIFO. Currently serial8250_do_set_termios() prevents to enable
> autoflow since the minimum requirement of 32 bytes of FIFO size.
>
> Decrease a FIFO size limitation to 16 bytes to allow autoflow control be
> enabled on such UARTs.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_port.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index e213da0..3f8121e 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2522,9 +2522,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
> * the trigger, or the MCR RTS bit is cleared. In the case where
> * the remote UART is not using CTS auto flow control, we must
> * have sufficient FIFO entries for the latency of the remote
> - * UART to respond. IOW, at least 32 bytes of FIFO.
> + * UART to respond. IOW, at least 16 bytes of FIFO.
> */
> - if (up->capabilities & UART_CAP_AFE && port->fifosize >= 32) {
> + if (up->capabilities & UART_CAP_AFE && port->fifosize >= 16) {
Let's just remove the fifosize test and rely on UART_CAP_AFE to enable
AFE. Please remove comment from "In the case where ..."
Also, I think the PORT_A7 port type should have UART_CAP_AFE commented out,
especially since/if the trigger level is 1 byte.
Regards,
Peter Hurley
> up->mcr &= ~UART_MCR_AFE;
> if (termios->c_cflag & CRTSCTS)
> up->mcr |= UART_MCR_AFE;
>
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