From 4018517a1a69a85c3d61b20fa02f187b80773137 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 18 Nov 2008 01:47:21 +0100 Subject: iwlagn: fix RX skb alignment So I dug deeper into the DMA problems I had with iwlagn and a kind soul helped me in that he said something about pci-e alignment and mentioned the iwl_rx_allocate function to check for crossing 4KB boundaries. Since there's 8KB A-MPDU support, crossing 4k boundaries didn't seem like something the device would fail with, but when I looked into the function for a minute anyway I stumbled over this little gem: BUG_ON(rxb->dma_addr & (~DMA_BIT_MASK(36) & 0xff)); Clearly, that is a totally bogus check, one would hope the compiler removes it entirely. (Think about it) After fixing it, I obviously ran into it, nothing guarantees the alignment the way you want it, because of the way skbs and their headroom are allocated. I won't explain that here nor double-check that I'm right, that goes beyond what most of the CC'ed people care about. So then I came up with the patch below, and so far my system has survived minutes with 64K pages, when it would previously fail in seconds. And I haven't seen a single instance of the TX bug either. But when you see the patch it'll be pretty obvious to you why. This should fix the following reported kernel bugs: http://bugzilla.kernel.org/show_bug.cgi?id=11596 http://bugzilla.kernel.org/show_bug.cgi?id=11393 http://bugzilla.kernel.org/show_bug.cgi?id=11983 I haven't checked if there are any elsewhere, but I suppose RHBZ will have a few instances too... I'd like to ask anyone who is CC'ed (those are people I know ran into the bug) to try this patch. I am convinced that this patch is correct in spirit, but I haven't understood why, for example, there are so many unmap calls. I'm not entirely convinced that this is the only bug leading to the TX reply errors. Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- drivers/net/wireless/iwlwifi/iwl-dev.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/net/wireless/iwlwifi/iwl-dev.h') diff --git a/drivers/net/wireless/iwlwifi/iwl-dev.h b/drivers/net/wireless/iwlwifi/iwl-dev.h index c018121085e9..9966d4e384ce 100644 --- a/drivers/net/wireless/iwlwifi/iwl-dev.h +++ b/drivers/net/wireless/iwlwifi/iwl-dev.h @@ -89,7 +89,8 @@ extern struct iwl_cfg iwl5100_abg_cfg; #define DEFAULT_LONG_RETRY_LIMIT 4U struct iwl_rx_mem_buffer { - dma_addr_t dma_addr; + dma_addr_t real_dma_addr; + dma_addr_t aligned_dma_addr; struct sk_buff *skb; struct list_head list; }; -- cgit v1.2.2