[PATCH 3.10 26/77] matroxfb: perform a dummy read of M_STATUS

Greg Kroah-Hartman
2014-06-28T17:48:00Z

From: Mikulas Patocka <mpatocka@redhat.com>

commit 972754cfaee94d6e25acf94a497bc0a864d91b7e 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>

---
drivers/video/matrox/matroxfb_base.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/video/matrox/matroxfb_base.h
+++ b/drivers/video/matrox/matroxfb_base.h
@@ -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