drm: radeon: Fix unaligned access in r300_scratch().

In compat mode, the cmdbuf->buf 64-bit address cookie can
potentially be only 32-bit aligned.  Dereferencing this as
64-bit causes expensive unaligned traps on platforms like
sparc64.

Use get_unaligned() to fix.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/r300_cmdbuf.c

@@ -37,6 +37,8 @@
 #include "radeon_drv.h"
 #include "r300_reg.h"
 
+#include <asm/unaligned.h>
+
 #define R300_SIMULTANEOUS_CLIPRECTS		4
 
 /* Values for R300_RE_CLIPRECT_CNTL depending on the number of cliprects
@@ -917,6 +919,7 @@ static int r300_scratch(drm_radeon_private_t *dev_priv,
 {
 	u32 *ref_age_base;
 	u32 i, buf_idx, h_pending;
+	u64 ptr_addr;
 	RING_LOCALS;
 
 	if (cmdbuf->bufsz <
@@ -930,7 +933,8 @@ static int r300_scratch(drm_radeon_private_t *dev_priv,
 
 	dev_priv->scratch_ages[header.scratch.reg]++;
 
-	ref_age_base =  (u32 *)(unsigned long)*((uint64_t *)cmdbuf->buf);
+	ptr_addr = get_unaligned((u64 *)cmdbuf->buf);
+	ref_age_base = (u32 *)(unsigned long)ptr_addr;
 
 	cmdbuf->buf += sizeof(u64);
 	cmdbuf->bufsz -= sizeof(u64);