linux-kernel - Re: 6175ddf06b6172046a329e3abfd9c901a43efd2e breaks matroxfb console

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Message-Id: <201008032034.30335.linux@rainbow-software.org>
Date:	Tue, 3 Aug 2010 20:34:27 +0200
From:	Ondrej Zary <linux@...nbow-software.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	brgerst@...il.com,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: 6175ddf06b6172046a329e3abfd9c901a43efd2e breaks matroxfb console

On Monday 02 August 2010 23:42:29 H. Peter Anvin wrote:
> On 08/02/2010 02:35 PM, Ondrej Zary wrote:
> > The patch below fixes it for me. Is it correct on all architectures?
> >
> > --- linux-2.6.35-rc2/drivers/video/matrox/matroxfb_base.h	2010-06-06
> > 05:43:24.000000000 +0200 +++
> > linux-2.6.35-rc3/drivers/video/matrox/matroxfb_base.h	2010-08-02
> > 23:31:34.000000000 +0200 @@ -157,7 +157,7 @@ static inline void
> > mga_memcpy_toio(vaddr
> >  	 *  (3) It copes with unaligned source (destination is guaranteed to be
> > page *      aligned and length is guaranteed to be multiple of 4). */
> > -	memcpy_toio(va.vaddr, src, len);
> > +	iowrite32_rep(va.vaddr, src, len);
> >  #else
> >          u_int32_t __iomem* addr = va.vaddr;
>
> I don't think so; in particular I don't *think* non-x86 architectures
> will deal with the requirement that it handles an unaligned source.  As
> such, the #if would still be necessary; the #else clause could be
> replaced with a get_unaligned() ... iowrite32() loop.

Just tested the #else part on sparc and it seems to work fine - so I'm not going to touch (break) it.

> The other thing to watch out for is that "len" passed to iowrite32_rep()
> is a count of 32-bit words, whereas memcpy_toio() takes a byte count...
> you need to >> 2 there.

Thanks.

Here's v2 patch:


Fix incorrect use of memcpy_toio() in matroxfb that broke in 2.6.34.

Signed-off-by: Ondrej Zary <linux@...nbow-software.org>

--- linux-2.6.35-rc2/drivers/video/matrox/matroxfb_base.h	2010-06-06 05:43:24.000000000 +0200
+++ linux-2.6.35-rc3/drivers/video/matrox/matroxfb_base.h	2010-08-03 18:13:46.000000000 +0200
@@ -151,13 +151,13 @@ static inline void mga_writel(vaddr_t va
 static inline void mga_memcpy_toio(vaddr_t va, const void* src, int len) {
 #if defined(__alpha__) || defined(__i386__) || defined(__x86_64__)
 	/*
-	 * memcpy_toio works for us if:
+	 * iowrite32_rep works for us if:
 	 *  (1) Copies data as 32bit quantities, not byte after byte,
 	 *  (2) Performs LE ordered stores, and
 	 *  (3) It copes with unaligned source (destination is guaranteed to be page
 	 *      aligned and length is guaranteed to be multiple of 4).
 	 */
-	memcpy_toio(va.vaddr, src, len);
+	iowrite32_rep(va.vaddr, src, len >> 2);
 #else
         u_int32_t __iomem* addr = va.vaddr;
 


-- 
Ondrej Zary
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