Re: [PATCH v2] serial: OMAP: add RS485 support

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On Tue, Aug 13, 2013 at 12:22 PM, Mark Jackson <mpfj-list@xxxxxxxxxxxxx> wrote:
> On 12/08/13 23:56, Greg KH wrote:
>> On Sun, Aug 11, 2013 at 02:56:50PM +0100, Mark Jackson wrote:
>>> This patch adds RS485 support to the OMAP serial driver, as
>>> defined in:-
>>>
>>> Documentation/devicetree/bindings/serial/rs485.txt
>>>
>>> When a UART transmitter is connected to (eg) a RS485 driver, it is
>>> necessary to turn the driver on/off as quickly as possible.  This is
>>> best achieved in the serial driver itself (rather than in userspace
>>> where the latency can be quite large).
>>>
>>> This patch allows a GPIO pin to be defined (via DT) that controls
>>> the enabling of the driver at the start of a message, and disables
>>> the driver when the message has been completed.
>>>
>>> When RS485 is disabled, the RTS pin is set to on.
>>>
>>> Signed-off-by: Mark Jackson <mpfj@xxxxxxxxxxxxx>
>>> ---
>>> Changes in v2:
>>> - Fix incorrect logic in serial_omap_config_rs485()
>>>
>>>  drivers/tty/serial/omap-serial.c |  178 ++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 178 insertions(+)
>>
>> This doesn't apply to my tty-next branch:
>>       checking file drivers/tty/serial/omap-serial.c
>>       Hunk #1 FAILED at 40.
>>       Hunk #2 succeeded at 162 (offset 6 lines).
>>       Hunk #3 succeeded at 280 (offset 5 lines).
>>       Hunk #4 succeeded at 378 (offset 6 lines).
>>       Hunk #5 succeeded at 1312 (offset 8 lines).
>>       Hunk #6 succeeded at 1405 (offset 8 lines).
>>       Hunk #7 succeeded at 1528 (offset 10 lines).
>>       Hunk #8 FAILED at 1638.
>>       Hunk #9 succeeded at 1705 (offset 6 lines).
>>       2 out of 9 hunks FAILED
>>
>> so I can't apply it, sorry.
>
> It was applied on top of Linus' tree, if that makes any difference.
>
> I'll rebase onto yours and re-post the patch.
> --

Hi Mark,

I've seen several attempts to add RS485 support to the omap serial
driver and it is always nack-ed. There seems to be concerns about
controlling the RTS by software when RS485 is not supported by the
UART hardware. Please refer to [1] and [2] for more information.

Best regards,
Javier

[1]: http://comments.gmane.org/gmane.linux.serial/6770
[2]: http://article.gmane.org/gmane.linux.serial/3619/
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