Any more comments on this from anyone before I submit v5? On 8/1/2014 9:44 AM, Olav Haugan wrote: > Hi Will, > > On 8/1/2014 1:22 AM, Will Deacon wrote: >> Hi Olav, >> >> On Fri, Aug 01, 2014 at 01:54:44AM +0100, Olav Haugan wrote: >>> Mapping and unmapping are more often than not in the critical path. >>> map_sg and unmap_sg allows IOMMU driver implementations to optimize >>> the process of mapping and unmapping buffers into the IOMMU page tables. >>> >>> Instead of mapping a buffer one page at a time and requiring potentially >>> expensive TLB operations for each page, this function allows the driver >>> to map all pages in one go and defer TLB maintenance until after all >>> pages have been mapped. >>> >>> Additionally, the mapping operation would be faster in general since >>> clients does not have to keep calling map API over and over again for >>> each physically contiguous chunk of memory that needs to be mapped to a >>> virtually contiguous region. >> >> Just a couple of minor comments, but I think this is almost there now. >> >>> Signed-off-by: Olav Haugan <[email protected]> >>> --- >>> drivers/iommu/iommu.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ >>> include/linux/iommu.h | 28 ++++++++++++++++++++++++++++ >>> 2 files changed, 72 insertions(+) >>> >>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >>> index 1698360..1d5dc2e 100644 >>> --- a/drivers/iommu/iommu.c >>> +++ b/drivers/iommu/iommu.c >>> @@ -1088,6 +1088,50 @@ size_t iommu_unmap(struct iommu_domain *domain, >>> unsigned long iova, size_t size) >>> } >>> EXPORT_SYMBOL_GPL(iommu_unmap); >>> >>> +int iommu_map_sg(struct iommu_domain *domain, unsigned long iova, >>> + struct scatterlist *sg, unsigned int nents, >>> + int prot, unsigned long flags) >>> +{ >> >> What do you anticipate passing in the flags parameter? I assume it's >> something specific to the scatterlist, since we can't provide this to >> iommu_map as it stands? > > Initially the flags argument is planned to be used by clients to > indicate to the driver that no TLB operation is necessary. This allows > clients to for example map/unmap multiple scatter-gather lists without > doing expensive TLB invalidate operations for each call but just do this > at the last mapping/unmapping call instead. I believe Rob Clark was > looking for this feature and I can see the benefit for our use cases also. > >>> + int ret = 0; >>> + unsigned long offset = 0; >>> + >>> + if (unlikely(domain->ops->map_sg == NULL)) { >>> + unsigned int i; >>> + struct scatterlist *s; >>> + >>> + for_each_sg(sg, s, nents, i) { >>> + phys_addr_t phys = page_to_phys(sg_page(s)); >>> + size_t page_len = s->offset + s->length; >>> + >>> + ret = iommu_map(domain, iova + offset, phys, page_len, >>> + prot); >>> + if (ret) >>> + goto fail; >>> + >>> + offset += page_len; >>> + } >>> + } else { >>> + ret = domain->ops->map_sg(domain, iova, sg, nents, prot, flags); >>> + } >>> + goto out; >>> + >>> +fail: >>> + /* undo mappings already done in case of error */ >>> + iommu_unmap(domain, iova, offset); >> >> I think this would be cleaner if you stuck it in the loop above and removed >> all these labels: >> >> if (ret) { >> iommu_unmap(...); >> break; >> } > > Sure, I can do that. > > Thanks, > > Olav >
Olav -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
