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@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/video/matrox/matroxfb_base.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-3.14/drivers/video/matrox/matroxfb_base.h
===================================================================
--- linux-3.14.orig/drivers/video/matrox/matroxfb_base.h 2014-04-08 00:35:19.460051657 +0200
+++ linux-3.14/drivers/video/matrox/matroxfb_base.h 2014-05-03 18:38:18.882396833 +0200
@@ -698,7 +698,7 @@ void matroxfb_unregister_driver(struct m
#define mga_fifo(n) do {} while ((mga_inl(M_FIFOSTATUS) & 0xFF) < (n))
-#define WaitTillIdle() do {} while (mga_inl(M_STATUS) & 0x10000)
+#define WaitTillIdle() do { mga_inl(M_STATUS); do {} while (mga_inl(M_STATUS) & 0x10000); } while (0)
/* code speedup */
#ifdef CONFIG_FB_MATROX_MILLENIUM
--
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