rtl8187: fix crashes on mips caused by misaligned DMA and cache issues

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 39570

package/kernel/mac80211/patches/300-pending_work.patch

@@ -1,3 +1,43 @@
+commit d4426800f71e972feaa33e04c5801fc730627bdd
+Author: Stanislaw Gruszka <stf_xl@wp.pl>
+Date:   Mon Feb 10 22:38:28 2014 +0100
+
+    rtl8187: fix regression on MIPS without coherent DMA
+    
+    This patch fixes regression caused by commit a16dad77634 "MIPS: Fix
+    potencial corruption". That commit fixes one corruption scenario in
+    cost of adding another one, which actually start to cause crashes
+    on Yeeloong laptop when rtl8187 driver is used.
+    
+    For correct DMA read operation on machines without DMA coherence, kernel
+    have to invalidate cache, such it will refill later with new data that
+    device wrote to memory, when that data is needed to process. We can only
+    invalidate full cache line. Hence when cache line includes both dma
+    buffer and some other data (written in cache, but not yet in main
+    memory), the other data can not hit memory due to invalidation. That
+    happen on rtl8187 where struct rtl8187_priv fields are located just
+    before and after small buffers that are passed to USB layer and DMA
+    is performed on them.
+    
+    To fix the problem we align buffers and reserve space after them to make
+    them match cache line.
+    
+    This patch does not resolve all possible MIPS problems entirely, for
+    that we have to assure that we always map cache aligned buffers for DMA,
+    what can be complex or even not possible. But patch fixes visible and
+    reproducible regression and seems other possible corruptions do not
+    happen in practice, since Yeeloong laptop works stable without rtl8187
+    driver.
+    
+    Bug report:
+    https://bugzilla.kernel.org/show_bug.cgi?id=54391
+    
+    Reported-by: Petr Pisar <petr.pisar@atlas.cz>
+    Bisected-by: Tom Li <biergaizi2009@gmail.com>
+    Reported-and-tested-by: Tom Li <biergaizi2009@gmail.com>
+    Cc: stable@vger.kernel.org
+    Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
+
 commit e2f141d67ad1e7fe10aaab61811e8a409dfb2442
 Author: Sujith Manoharan <c_manoha@qca.qualcomm.com>
 Date:   Fri Feb 7 10:29:55 2014 +0530
@@ -2632,3 +2672,36 @@ Date:   Thu Jan 23 20:06:34 2014 +0100
  	/* Revert chainmask to runtime parameters */
  	ar9003_hw_set_chain_masks(ah, ah->rxchainmask, ah->txchainmask);
  
+--- a/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h
++++ b/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h
+@@ -15,6 +15,8 @@
+ #ifndef RTL8187_H
+ #define RTL8187_H
+ 
++#include <linux/cache.h>
++
+ #include "rtl818x.h"
+ #include "leds.h"
+ 
+@@ -139,7 +141,10 @@ struct rtl8187_priv {
+ 	u8 aifsn[4];
+ 	u8 rfkill_mask;
+ 	struct {
+-		__le64 buf;
++		union {
++			__le64 buf;
++			u8 dummy1[L1_CACHE_BYTES];
++		} ____cacheline_aligned;
+ 		struct sk_buff_head queue;
+ 	} b_tx_status; /* This queue is used by both -b and non-b devices */
+ 	struct mutex io_mutex;
+@@ -147,7 +152,8 @@ struct rtl8187_priv {
+ 		u8 bits8;
+ 		__le16 bits16;
+ 		__le32 bits32;
+-	} *io_dmabuf;
++		u8 dummy2[L1_CACHE_BYTES];
++	} *io_dmabuf ____cacheline_aligned;
+ 	bool rfkill_off;
+ 	u16 seqno;
+ };