linux-kernel - Re: 6175ddf06b6172046a329e3abfd9c901a43efd2e breaks matroxfb console

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Date:	Mon, 2 Aug 2010 23:14:24 +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 23:04:28 H. Peter Anvin wrote:
> On 08/02/2010 12:49 PM, Ondrej Zary wrote:
> > Hello,
> > matroxfb (at least with Mystique and Mystique 220) stopped working in
> > 2.6.34 - the screen is completely corrupted. Bisection shows that
> > 6175ddf06b6172046a329e3abfd9c901a43efd2e is first bad commit.
> >
> > Reverting 6175ddf06b6172046a329e3abfd9c901a43efd2e in 2.6.34 fixes the
> > problem (1c5b9069e12e20d2fe883076ae0bf73966492108 must be reverted
> > first).
>
> Sounds like another driver which used memcpy_toio() when it should have
> used iowrite32_rep() or __iowrite32_copy().
>
> Hmm... is __iowrite32_copy() and iowrite32_rep() redundant?  If so, we
> should get rid of the former.

There is a wrapper in drivers/video/matrox/matroxfb_base.h (see below) with
some comment. So this commit changed one of the three points?

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:
         *  (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);
#else
        u_int32_t __iomem* addr = va.vaddr;

        if ((unsigned long)src & 3) {
                while (len >= 4) {
                        fb_writel(get_unaligned((u32 *)src), addr);
                        addr++;
                        len -= 4;
                        src += 4;
                }
        } else {
                while (len >= 4) {
                        fb_writel(*(u32 *)src, addr);
                        addr++;
                        len -= 4;
                        src += 4;
                }
        }
#endif
}

-- 
Ondrej Zary
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