linux-kernel - Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)

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Message-ID: <11273481.VQZWGoSGBC@wuerfel>
Date:	Thu, 07 Feb 2013 01:34:37 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Michal Simek <monstr@...str.eu>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	dahinds@...rs.sourceforge.net
Subject: Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be)

On Wednesday 06 February 2013 17:21:37 Michal Simek wrote:

> I have looked at the patches from more practical side and I have tested it on
> microblaze big endian in 16bit mode and I have found that sysace driver
> stop to work.
> After that I have looked at ioread/iowrite microblaze implementation
> and implementation of that functions is wrong.
> I have fixed it but looking at using asm-generic/io.h for microblaze.
> 
> I will do more tests and let you know.

Well, I think they are only wrong in the way that they ignore
endianess. You can fix that by changing them to be identical
to the in_le/in_be families.

However, I would also recommend changing your __raw_* accessors
to inline assembly functions rather than pointer dereferences,
because we have had problems in the past where gcc (when faced
with undefined C) silently turned 32-bit accesses into multiples
of byte accesses, which can be fatal for MMIO. The asm-generic
version obviously cannot get this right.

The PCI I/O space handling, as mentioned, is completely broken
on microblaze, and you can either use the approach from asm-generic
when you set PCI_IOBASE match your isa_io_base.

	Arnd
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