Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485 direction control

From	Peter Hurley <peter@hurleysoftware.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485 direction control
Date	2016-02-18 18:00 +0100
Message-ID	<r3A5S-8tj-29@gated-at.bofh.it> (permalink)
References	(3 earlier) <r1gNY-3W4-5@gated-at.bofh.it> <r1imK-54w-3@gated-at.bofh.it> <r3dCj-Fn-7@gated-at.bofh.it> <r3r2y-229-7@gated-at.bofh.it> <r3tnH-3zl-1@gated-at.bofh.it>
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On 02/18/2016 01:46 AM, Ильяс Гасанов wrote:
> 2016-02-18 10:18 GMT+03:00 Ильяс Гасанов <torso.nafi@gmail.com>:
>> Also, forgot to mention that if serial8250_em485_init is called not
>> upon uart startup but elsewhere (upon port register for example), and
>> em485 is set, serial8250_do_startup should call
>> serial8250_em485_rts_after_send, or else RTS might be in wrong state
>> whenever the port device is opened, making it impossible to receive
>> data through RTS-controlled RS232<->RS485 hardware converters.
> 
> Just found out that it doesn't help. Actually, it is the behavior of
> tty_open function to call tty_port_block_til_ready after startup, and
> of the latter - to set RTS via ioctl if baud is not zero - both of
> which cannot be overriden within the scope of the 8250 framework. The
> reason this works in legacy omap_serial is that my GPIO which is used
> to emulate RTS is not tied to mctrl there, so the call of
> tty_port_block_til_ready does not affect its state.
> 
> Therefore, a check for SER_RS485_ENABLED needs to be introduced to
> tty_port_block_til_ready.

No, that's not the way.

First, there's plenty of driver hooks to properly manage the RTS level
for rs485.
Second, how are you running GPIO rts with the omap8250 driver?

Thread

Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-11 17:50 +0100
  Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control "Matwey V. Kornilov" <matwey@sai.msu.ru> - 2016-02-11 20:10 +0100
    Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-11 21:30 +0100
      Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control "Matwey V. Kornilov" <matwey@sai.msu.ru> - 2016-02-12 09:00 +0100
        Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-12 10:40 +0100
          Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-17 18:00 +0100
            Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 08:20 +0100
              Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 10:50 +0100
                Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Peter Hurley <peter@hurleysoftware.com> - 2016-02-18 18:00 +0100
                Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 19:20 +0100

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