On Mon, 18 Aug 2008 00:48:05 +0900 FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> wrote: > On Sun, 17 Aug 2008 17:42:13 +0200 > Ingo Molnar <mingo@xxxxxxx> wrote: > > > > > * FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> wrote: > > > > > The above commit log of Prarit's patch is completely wrong (so I wrote > > > this patch). To avoid misunderstanding, can you apply this patch with > > > a proper description like this: > > > > sure, i've created the commit below - is that fine? > > > > Ingo > > I think that 'v2' in the subject is unnecessary. The rest looks fine. > > Thanks, > > > > ---------------> > > From 3f18931be15856db01a216995670412e4421f3c9 Mon Sep 17 00:00:00 2001 > > From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> > > Date: Mon, 18 Aug 2008 00:36:18 +0900 > > Subject: [PATCH] x86 gart: allocate size-aligned address for alloc_coherent, v2 > > > > This patch changes GART IOMMU to return a size aligned address wrt > > dma_alloc_coherent, as DMA-mapping.txt defines: > > > > The cpu return address and the DMA bus master address are both > > guaranteed to be aligned to the smallest PAGE_SIZE order which > > is greater than or equal to the requested size. This invariant > > exists (for example) to guarantee that if you allocate a chunk > > which is smaller than or equal to 64 kilobytes, the extent of the > > buffer you receive will not cross a 64K boundary. Ops, can you remove the following part? I confused segment_boundary_mask with max_segment_size. A device needs to set segment_boundary_mask properly if it doesn't want a buffer that crosses a 64K boundary. We set the default boundary to 4G. > > But it is very unlikely that this matters. As DMA-mapping.txt > > explains, This invariant is to avoid the boundary problem (such as > > 64K). Now the majority of IOMMUs including GART (except for Intel > > IOMMU) don't allocate a buffer that crosses a 64K boundary wrt all the > > DMA mapping interfaces (dma_alloc_coherent, dma_map_sg, and > > dma_map_single) because of segment_boundary_mask in struct > > device_dma_parameters. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
