From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754781Ab1AFHpr (ORCPT ); Thu, 6 Jan 2011 02:45:47 -0500 Received: from [69.28.251.93] ([69.28.251.93]:38686 "EHLO b32.net" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754482Ab1AFHpp (ORCPT ); Thu, 6 Jan 2011 02:45:45 -0500 X-Greylist: delayed 401 seconds by postgrey-1.27 at vger.kernel.org; Thu, 06 Jan 2011 02:45:45 EST From: Kevin Cernekee To: Ralf Baechle Cc: , , , , Subject: [PATCH RESEND 1/6] MIPS: sync after cacheflush Date: Wed, 05 Jan 2011 23:31:25 -0800 Message-Id: <8eec0c63f92528c501c0e6a0c8396359@localhost> User-Agent: vim 7.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On processors with deep write buffers, it is likely that many cycles will pass between a CACHE instruction and the time the data actually gets written out to DRAM. Add a SYNC instruction to ensure that the buffers get emptied before the flush functions return. Actual problem seen in the wild: 1) dma_alloc_coherent() allocates cached memory 2) memset() is called to clear the new pages 3) dma_cache_wback_inv() is called to flush the zero data out to memory 4) dma_alloc_coherent() returns an uncached (kseg1) pointer to the freshly allocated pages 5) Caller writes data through the kseg1 pointer 6) Buffered writeback data finally gets flushed out to DRAM 7) Part of caller's data is inexplicably zeroed out This patch adds SYNC between steps 3 and 4, which fixed the problem. Signed-off-by: Kevin Cernekee --- arch/mips/mm/c-r4k.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c index b4923a7..dc5d9c4 100644 --- a/arch/mips/mm/c-r4k.c +++ b/arch/mips/mm/c-r4k.c @@ -604,6 +604,7 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size) r4k_blast_scache(); else blast_scache_range(addr, addr + size); + __sync(); return; } @@ -620,6 +621,7 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size) } bc_wback_inv(addr, size); + __sync(); } static void r4k_dma_cache_inv(unsigned long addr, unsigned long size) @@ -647,6 +649,7 @@ static void r4k_dma_cache_inv(unsigned long addr, unsigned long size) (addr + size - 1) & almask); blast_inv_scache_range(addr, addr + size); } + __sync(); return; } @@ -663,6 +666,7 @@ static void r4k_dma_cache_inv(unsigned long addr, unsigned long size) } bc_inv(addr, size); + __sync(); } #endif /* CONFIG_DMA_NONCOHERENT */ -- 1.7.0.4