matroxfb: perform a dummy read of M_STATUS

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commit 972754cfae upstream.

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>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Mikulas Patocka 2014-05-15 06:58:24 -04:00 • committed by Greg Kroah-Hartman

parent feb62c88c9

commit da818b18f1

1 changed files with 1 additions and 1 deletions

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drivers/video/fbdev/matrox/matroxfb_base.h

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