On Sun, Dec 11, 2016 at 08:57:35PM +1100, Daniel Jędrychowski wrote:
> When in RS485 emulation mode, __do_stop_tx_rs485() calls serial8250_clear_fifos
> ().
> This not only clears the FIFOs, but also sets all bits in their control
> register (UART_FCR) to 0.
>
> One of the effects of this is the disabling of the FIFOs, which turns them into
> single-byte holding registers.
> The rest of the driver doesn't know this, which results in the lions share of
> characters passed into a write call to be dropped.
>
> (I can supply logic analyzer screenshots if necessary)
>
> This fix replaces the serial8250_clear_fifos() call to
> serial8250_clear_and_reinit_fifos() - this prevents the "dropped characters"
> issue from manifesting again while retaining the requirement of clearing the RX
> FIFO after transmission if the SER_RS485_RX_DURING_TX flag is disabled.
Odd, why has no one else seen this before? Any idea how it could have
ever worked properly in the past? Has anything changed in this area
recently?
> (P.S. This is the first time submitting a patch for me. Apologies if I missed
> something in the formatting or if the description is unclear)
No need for this "P.S." in the changelog, you can put that below the ---
line if you want to make comments that do not show up in the commit.
>
> Signed-off-by: Daniel Jedrychowski <avistel@xxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_port.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/
> 8250_port.c
> index 1731b98..080d5a5 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -1411,7 +1411,7 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p)
> * Enable previously disabled RX interrupts.
> */
> if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
> - serial8250_clear_fifos(p);
> + serial8250_clear_and_reinit_fifos(p);
>
> p->ier |= UART_IER_RLSI | UART_IER_RDI;
> serial_port_out(&p->port, UART_IER, p->ier);
Hm, something went wrong with your patch and the tabs got turned into
spaces so it can't be applied :(
Can you try not using the web interface for gmail? It's known to be
broken for patches (see Documentation/email_clients.txt for details.)
thanks,
greg k-h
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