linux-kernel - Re: [PATCH v6] serial: rewrite pxa2xx-uart to use 8250

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Date:	Mon, 22 Feb 2016 08:17:33 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sergei Ianovich <ynvich@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	James Cameron <quozl@...top.org>,
	Russell King <linux@....linux.org.uk>,
	Jiri Slaby <jslaby@...e.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Joachim Eastwood <manabian@...il.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Scott Wood <scottwood@...escale.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Paul Burton <paul.burton@...tec.com>,
	Mans Rullgard <mans@...sr.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Peter Hurley <peter@...leysoftware.com>,
	"open list\:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v6] serial: rewrite pxa2xx-uart to use 8250_core

Sergei Ianovich <ynvich@...il.com> writes:

> On Sat, 2016-02-06 at 22:22 -0800, Greg Kroah-Hartman wrote:
>> On Thu, Dec 24, 2015 at 06:15:14PM +0300, Sergei Ianovich wrote:
>> > pxa2xx-uart was a separate uart platform driver. It was declaring
>> > the same device names and numbers as 8250 driver. As a result,
>> > it was impossible to use 8250 driver on PXA SoCs.
>> > 
>> > Upon closer examination pxa2xx-uart turned out to be a clone of
>> > 8250_core driver.
>> > 
>> > Workaround for Erratum #19 according to Marvel(R) PXA270M Processor
>> > Specification Update (April 19, 2010) is dropped. 8250_core reads
>> > from FIFO immediately after checking DR bit in LSR.
>> > 
>> > The patch leaves the original SERIAL_PXA driver around. The
>> > original
>> > driver is just marked DEPRECATED in Kconfig and C source. When
>> > the original driver is considered safe to remove, no changes
>> > to SERIAL_8250 will be necessary.
>> 
>> But, you just broke existing configurations, right?  The serial port is
>> a different name now, are you willing to handle the angry users?
>
> No, the port name remains /dev/ttyS0. In fact, this conflict (both
> drivers use the same name and char major) is the reason for the patch.
> Noone should notice the change at runtime. There will be a warning at
> compile time which should make the transition to the new driver faster.
>
>> If so, great, get the platform maintainer to sign off on this please and
>> then resend it.

If you're talking about the PXA maintainer, then :
Acked-by: Robert Jarzmik <robert.jarzmik@...e.fr>

I'm happy with the patch, all pxa board maintainers have been warned, and there
exists a fallback solution.

So let's go forward, and if people complain, let them complain and forward them
to me.

Cheers.

-- 
Robert