From mboxrd@z Thu Jan  1 00:00:00 1970
From: nicolas.ferre@atmel.com (Nicolas Ferre)
Date: Mon, 13 Jun 2016 11:51:43 +0200
Subject: [PATCH] tty/serial: atmel: fix RS485 half duplex with DMA
In-Reply-To: <57500D60.2000900@atmel.com>
References: <1464389648-4820-1-git-send-email-alexandre.belloni@free-electrons.com>
 <57500D60.2000900@atmel.com>
Message-ID: <575E822F.7050501@atmel.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Le 02/06/2016 12:41, Nicolas Ferre a ?crit :
> Le 28/05/2016 00:54, Alexandre Belloni a ?crit :
>> When using DMA, half duplex doesn't work properly because rx is not stopped
>> before starting tx. Ensure we call atmel_stop_rx() in the DMA case.
>>
>> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> 
> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> 
> We can also add:
> Cc: <stable@vger.kernel.org> # v4.3+
> 
> 
> Thanks Alexandre!

Greg,

It's not a regression but a good fix for this rs485 mode. So I suspect
it can still be queued for 4.7-rc... (aka: gentle ping).

Bye,

>> ---
>>  drivers/tty/serial/atmel_serial.c | 14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
>> index 954941dd8124..f9c798cba83f 100644
>> --- a/drivers/tty/serial/atmel_serial.c
>> +++ b/drivers/tty/serial/atmel_serial.c
>> @@ -482,19 +482,21 @@ static void atmel_start_tx(struct uart_port *port)
>>  {
>>  	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>>  
>> -	if (atmel_use_pdc_tx(port)) {
>> -		if (atmel_uart_readl(port, ATMEL_PDC_PTSR) & ATMEL_PDC_TXTEN)
>> -			/* The transmitter is already running.  Yes, we
>> -			   really need this.*/
>> -			return;
>> +	if (atmel_use_pdc_tx(port) && (atmel_uart_readl(port, ATMEL_PDC_PTSR)
>> +				       & ATMEL_PDC_TXTEN))
>> +		/* The transmitter is already running.  Yes, we
>> +		   really need this.*/
>> +		return;
>>  
>> +	if (atmel_use_pdc_tx(port) || atmel_use_dma_tx(port))
>>  		if ((port->rs485.flags & SER_RS485_ENABLED) &&
>>  		    !(port->rs485.flags & SER_RS485_RX_DURING_TX))
>>  			atmel_stop_rx(port);
>>  
>> +	if (atmel_use_pdc_tx(port))
>>  		/* re-enable PDC transmit */
>>  		atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTEN);
>> -	}
>> +
>>  	/* Enable interrupts */
>>  	atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask);
>>  }
>>
> 
> 


-- 
Nicolas Ferre