linux-kernel - [PATCH] vt_buffer: drop console buffer copying optimisations

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Date:	Thu, 29 Jan 2015 14:11:25 +1000
From:	Dave Airlie <airlied@...hat.com>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.sf.net,
	Dave Airlie <airlied@...hat.com>
Subject: [PATCH] vt_buffer: drop console buffer copying optimisations

These two copy to/from VGA memory, however on the Silicon
Motion SMI750 VGA card on a 64-bit system cause console corruption.

This is due to the hw being buggy and not handling a 64-bit transaction
correctly.

We could try and create a 32-bit version of these routines,
but I'm not sure the optimisation is worth much today.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1132826

Tested-by: Huawei engineering.
Signed-off-by: Dave Airlie <airlied@...hat.com>
---

Linus, this came up a while back I finally got some confirmation
that it fixes those servers.

 include/linux/vt_buffer.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/include/linux/vt_buffer.h b/include/linux/vt_buffer.h
index 057db7d..f38c10b 100644
--- a/include/linux/vt_buffer.h
+++ b/include/linux/vt_buffer.h
@@ -21,10 +21,6 @@
 #ifndef VT_BUF_HAVE_RW
 #define scr_writew(val, addr) (*(addr) = (val))
 #define scr_readw(addr) (*(addr))
-#define scr_memcpyw(d, s, c) memcpy(d, s, c)
-#define scr_memmovew(d, s, c) memmove(d, s, c)
-#define VT_BUF_HAVE_MEMCPYW
-#define VT_BUF_HAVE_MEMMOVEW
 #endif
 
 #ifndef VT_BUF_HAVE_MEMSETW
-- 
1.9.3

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