From: Mikulas Patocka Date: Thu, 15 May 2014 10:58:24 +0000 (-0400) Subject: matroxfb: perform a dummy read of M_STATUS X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=031767d310d44ec8e1e244ad8e8d0f5564f4a49a;p=linux-edison.git matroxfb: perform a dummy read of M_STATUS 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 Signed-off-by: Tomi Valkeinen Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/video/matrox/matroxfb_base.h b/drivers/video/matrox/matroxfb_base.h index 556d96ce40b..89a8a89a5eb 100644 --- a/drivers/video/matrox/matroxfb_base.h +++ b/drivers/video/matrox/matroxfb_base.h @@ -698,7 +698,7 @@ void matroxfb_unregister_driver(struct matroxfb_driver* drv); #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