2016-09-12 11:53 GMT+02:00 Alexandre Belloni
<alexandre.belloni@xxxxxxxxxxxxxxxxxx>:
> On 12/09/2016 at 11:47:33 +0200, Richard Genoud wrote :
>> Commit 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when
>> hardware handshake is enabled") broke the hardware handshake on SAM9x5
>> platforms.
>>
>> On Atmel platforms, the USART can only handle the handware handshake
>> (ATMEL_US_USMODE_HWHS) if FIFOs or PDC are used.
>>
>> Thus, ATMEL_US_USMODE_HWHS mode should only be used in this case.
>>
>> For SAM9x5, there's no FIFOs nor PDC for the USART, so the mode should
>> be ATMEL_US_USMODE_NORMAL and the RTS pin should be controlled by the
>> driver.
>>
>> NB: -stable is not Cced because it doesn't cleanly apply on 4.1+
>>
>> Tested on SAM9G35-CM with and without DMA
>>
>> Signed-off-by: Richard Genoud <richard.genoud@xxxxxxxxx>
>> Fixes: 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when hardware handshake is enabled")
>> ---
>> drivers/tty/serial/atmel_serial.c | 18 +++++++++++-------
>> 1 file changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
>> index e9b4fbf88c2d..32154e7231ce 100644
>> --- a/drivers/tty/serial/atmel_serial.c
>> +++ b/drivers/tty/serial/atmel_serial.c
>> @@ -2130,15 +2130,19 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
>> } else if ((termios->c_cflag & CRTSCTS) &&
>> !mctrl_gpio_use_rtscts(atmel_port->gpios)) {
>> /*
>> - * RS232 with hardware handshake (RTS/CTS)
>> - * handled by the controller.
>> + * Automatic hardware handshake (RTS/CTS) only work with
>> + * FIFOs or PDC.
>> + * Meaning that on SAM9x5 the controller can't handle
>> + * the hardware handshake (no FIFOs nor PDC on these platforms).
>> */
>> - if (atmel_use_dma_rx(port) && !atmel_use_fifo(port)) {
>> - dev_info(port->dev, "not enabling hardware flow control because DMA is used");
>> - termios->c_cflag &= ~CRTSCTS;
>> - } else {
>> + if (atmel_use_pdc_rx(port) || atmel_use_fifo(port))
>> mode |= ATMEL_US_USMODE_HWHS;
>> - }
>> + else
>> + /*
>> + * The hardware handshake won't be handle by the
>> + * controller but by the driver.
>> + */
>> + mode |= ATMEL_US_USMODE_NORMAL;
>
> You still need the case where HWHS is impossible and there are no gpio
> configured. You need to inform userspace that the configuration was not
> applied instead of silently ignoring the error.
Could you explain which case it is ?
The only one I can see is when there's no GPIO declared for RTS/CTS
AND, there's no pin muxed for RTS/CTS either.
Have you got another example in mind ?
>
>> } else {
>> /* RS232 without hadware handshake or controlled by GPIOs */
>> mode |= ATMEL_US_USMODE_NORMAL;
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
--
for me, ck means con kolivas and not calvin klein... does it mean I'm a geek ?
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