From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mikulas Patocka , Tomi Valkeinen Subject: [PATCH 3.14 040/110] matroxfb: perform a dummy read of M_STATUS Date: Sat, 28 Jun 2014 10:46:37 -0700 Message-Id: <20140628174547.554051497@linuxfoundation.org> In-Reply-To: <20140628174545.354748696@linuxfoundation.org> References: <20140628174545.354748696@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka 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 --- 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