linux-kernel - Re: [PATCH 1/2] serial: 8250: enable SERIAL_MCTRL

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Date:   Tue, 05 Jun 2018 13:00:42 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jslaby@...e.com>, Kees Cook <keescook@...omium.org>,
        Matthias Brugger <mbrugger@...e.com>,
        Allen Pais <allen.lkml@...il.com>, Sean Young <sean@...s.org>,
        Ed Blake <ed.blake@...drel.com>,
        Stefan Potyra <Stefan.Potyra@...ktrobit.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Joshua Scott <joshua.scott@...iedtelesis.co.nz>,
        Vignesh R <vigneshr@...com>,
        Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>,
        Aaron Sierra <asierra@...-inc.com>,
        Rafael Gago <rafael.gago@...il.com>,
        Joel Stanley <joel@....id.au>,
        Sean Wang <sean.wang@...iatek.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yegor Yefremov <yegorslists@...glemail.com>
Subject: Re: [PATCH 1/2] serial: 8250: enable SERIAL_MCTRL_GPIO by default.

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@...ux.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@...ux.intel.com>
Intel Finland Oy