From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759813AbYAGXeu (ORCPT ); Mon, 7 Jan 2008 18:34:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755519AbYAGXen (ORCPT ); Mon, 7 Jan 2008 18:34:43 -0500 Received: from gate.crashing.org ([63.228.1.57]:47069 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754905AbYAGXem (ORCPT ); Mon, 7 Jan 2008 18:34:42 -0500 Subject: [PATCH][POWERPC] Workaround for iommu page alignment (#2) From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Paul Mackerras Cc: linuxppc-dev list , Linux Kernel list In-Reply-To: <1199742359.6734.14.camel@pasglop> References: <1199742359.6734.14.camel@pasglop> Content-Type: text/plain Date: Tue, 08 Jan 2008 10:34:22 +1100 Message-Id: <1199748862.6734.20.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org powerpc: Workaround for iommu page alignment Our iommu page size is currently always 4K. That means with our current code, drivers may do a dma_map_sg() of a 64K page and obtain a dma_addr_t that is only 4K aligned. This works fine in most cases except some infiniband HW it seems, where they tell the HW about the page size and it ignores the low bits of the DMA address. This works around it by making our IOMMU code enforce a PAGE_SIZE alignment for mappings of objects that are page aligned in the first place and whose size is larger or equal to a page. Signed-off-by: Benjamin Herrenschmidt --- And this version actually does what the comment says (I had forgotten to quilt ref... a common mistake). Index: linux-work/arch/powerpc/kernel/iommu.c =================================================================== --- linux-work.orig/arch/powerpc/kernel/iommu.c 2007-12-21 10:39:39.000000000 +1100 +++ linux-work/arch/powerpc/kernel/iommu.c 2007-12-21 10:48:12.000000000 +1100 @@ -278,6 +278,7 @@ int iommu_map_sg(struct iommu_table *tbl unsigned long flags; struct scatterlist *s, *outs, *segstart; int outcount, incount, i; + unsigned int align; unsigned long handle; BUG_ON(direction == DMA_NONE); @@ -309,7 +310,12 @@ int iommu_map_sg(struct iommu_table *tbl /* Allocate iommu entries for that segment */ vaddr = (unsigned long) sg_virt(s); npages = iommu_num_pages(vaddr, slen); - entry = iommu_range_alloc(tbl, npages, &handle, mask >> IOMMU_PAGE_SHIFT, 0); + align = 0; + if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && slen >= PAGE_SIZE && + (vaddr & ~PAGE_MASK) == 0) + align = PAGE_SHIFT - IOMMU_PAGE_SHIFT; + entry = iommu_range_alloc(tbl, npages, &handle, + mask >> IOMMU_PAGE_SHIFT, align); DBG(" - vaddr: %lx, size: %lx\n", vaddr, slen); @@ -572,7 +578,7 @@ dma_addr_t iommu_map_single(struct iommu { dma_addr_t dma_handle = DMA_ERROR_CODE; unsigned long uaddr; - unsigned int npages; + unsigned int npages, align; BUG_ON(direction == DMA_NONE); @@ -580,8 +586,13 @@ dma_addr_t iommu_map_single(struct iommu npages = iommu_num_pages(uaddr, size); if (tbl) { + align = 0; + if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && size >= PAGE_SIZE && + ((unsigned long)vaddr & ~PAGE_MASK) == 0) + align = PAGE_SHIFT - IOMMU_PAGE_SHIFT; + dma_handle = iommu_alloc(tbl, vaddr, npages, direction, - mask >> IOMMU_PAGE_SHIFT, 0); + mask >> IOMMU_PAGE_SHIFT, align); if (dma_handle == DMA_ERROR_CODE) { if (printk_ratelimit()) { printk(KERN_INFO "iommu_alloc failed, "