Re: [PATCH 1/2] serial: 8250: enable SERIAL_MCTRL_GPIO by default.

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Giulio Benetti <giulio.benetti@micronovasrl.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>, Kees Cook <keescook@chromium.org>,
	Matthias Brugger <mbrugger@suse.com>,
	Allen Pais <allen.lkml@gmail.com>, Sean Young <sean@mess.org>,
	Ed Blake <ed.blake@sondrel.com>,
	Stefan Potyra <Stefan.Potyra@elektrobit.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Joshua Scott <joshua.scott@alliedtelesis.co.nz>,
	Vignesh R <vigneshr@ti.com>,
	Rolf Evers-Fischer <rolf.evers.fischer@aptiv.com>,
	Aaron Sierra <asierra@xes-inc.com>,
	Rafael Gago <rafael.gago@gmail.com>,
	Joel Stanley <joel@jms.id.au>, Sean Wang <sean.wang@mediatek.com>,
	linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
	Yegor Yefremov <yegorslists@googlemail.com>
Subject: Re: [PATCH 1/2] serial: 8250: enable SERIAL_MCTRL_GPIO by default.
Date: Tue, 05 Jun 2018 13:00:42 +0300	[thread overview]
Message-ID: <2b2a81ce166f16ab88a4733caed2544c8128ae6b.camel@linux.intel.com> (raw)
In-Reply-To: <7f4d688c-095a-d056-1edd-430bfc4e00da@micronovasrl.com>

On Mon, 2018-06-04 at 20:57 +0200, Giulio Benetti wrote:
> Il 04/06/2018 13:49, Andy Shevchenko ha scritto:
> > On Fri, 2018-06-01 at 16:11 +0200, Giulio Benetti wrote:
> > > It can be useful to override 8250 mctrl lines with gpios, for rts
> > > on
> > > rs485 for example, when rts is not mapped correctly to HW RTS pin.
> > > 
> > > Enable SERIAL_MCTRL_GPIO by default.
> > > 
> > 
> > Unfortunately NAK, see
> > 
> > commit 5db4f7f80d165fc9725f356e99feec409e446baa
> > Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Date:   Tue Aug 16 15:06:54 2016 +0300
> > 
> >      Revert "tty/serial/8250: use mctrl_gpio helpers"
> > 
> > for the details.
> > 
> > I would love to see a solution that will satisfy everyone, though I
> > have
> > only means to test proposals for now.
> 
> Thanks for pointing me that.
> I would try to solve serial breakage on intel with already extisting 
> patches dropping this one.
> I'm going to try.
> 
> I can't understand if it's enough using qemu x86 to reproduce the bug.
> If so I'm going to debug and check what makes driver to fail.

You need to provide an ACPI table with UART contains GpioInt() or
GpioIo() resource in it.

Where GPIO number is a number of pin related to UART's RxD.

> Do you think it makes sense? Would it be accepted after bug fixing?

I can test on our hardware. Can't say about the rest, though.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy