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Date: Thu, 18 Feb 2016 12:46:40 +0300 From: Ильяс Гасанов <torso.nafi@...il.com> To: "Matwey V. Kornilov" <matwey@....msu.ru> Cc: Greg KH <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.com>, Peter Hurley <peter@...leysoftware.com>, Andy Shevchenko <andy.shevchenko@...il.com>, One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>, linux-kernel <linux-kernel@...r.kernel.org>, linux-serial@...r.kernel.org Subject: Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485 direction control 2016-02-18 10:18 GMT+03:00 Ильяс Гасанов <torso.nafi@...il.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. Regards, Ilyas G.
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