matroxfb: perform a dummy read of M_STATUS
I had occasional screen corruption with the matrox framebuffer driver and I found out that the reason for the corruption is that the hardware blitter accesses the videoram while it is being written to. The matrox driver has a macro WaitTillIdle() that should wait until the blitter is idle, but it sometimes doesn't work. I added a dummy read mga_inl(M_STATUS) to WaitTillIdle() to fix the problem. The dummy read will flush the write buffer in the PCI chipset, and the next read of M_STATUS will return the hardware status. Since applying this patch, I had no screen corruption at all. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
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@ -698,7 +698,7 @@ void matroxfb_unregister_driver(struct matroxfb_driver* drv);
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#define mga_fifo(n) do {} while ((mga_inl(M_FIFOSTATUS) & 0xFF) < (n))
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#define WaitTillIdle() do {} while (mga_inl(M_STATUS) & 0x10000)
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#define WaitTillIdle() do { mga_inl(M_STATUS); do {} while (mga_inl(M_STATUS) & 0x10000); } while (0)
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/* code speedup */
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#ifdef CONFIG_FB_MATROX_MILLENIUM
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