From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Thu, 18 Jun 2015 17:54:29 +0100 Subject: [PATCH v2 2/4] iommu: Implement common IOMMU ops for DMA mapping In-Reply-To: <1434639625.26953.12.camel@mhfsdcap03> References: <1434639625.26953.12.camel@mhfsdcap03> Message-ID: <5582F7C5.8060901@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 18/06/15 16:00, Yong Wu wrote: > Hi Robin, > while our drm test, we meet a problem while dma-mmap. > > On Thu, 2015-06-11 at 16:54 +0100, Robin Murphy wrote: >> Taking inspiration from the existing arch/arm code, break out some >> generic functions to interface the DMA-API to the IOMMU-API. This will >> do the bulk of the heavy lifting for IOMMU-backed dma-mapping. >> >> Signed-off-by: Robin Murphy >> --- >> drivers/iommu/Kconfig | 7 + >> drivers/iommu/Makefile | 1 + >> drivers/iommu/dma-iommu.c | 560 ++++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/dma-iommu.h | 94 ++++++++ >> 4 files changed, 662 insertions(+) >> create mode 100644 drivers/iommu/dma-iommu.c >> create mode 100644 include/linux/dma-iommu.h >> > [snip] >> +/** >> + * iommu_dma_mmap - Map a buffer into provided user VMA >> + * @pages: Array representing buffer from iommu_dma_alloc() >> + * @size: Size of buffer in bytes >> + * @vma: VMA describing requested userspace mapping >> + * >> + * Maps the pages of the buffer in @pages into @vma. The caller is responsible >> + * for verifying the correct size and protection of @vma beforehand. >> + */ >> + >> +int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma) >> +{ >> + unsigned long uaddr = vma->vm_start; >> + unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT; >> + int ret = -ENXIO; >> + >> + for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) { > Is it : for (i = 0; i < count && uaddr < vma->vm_end; i++) According to the patches at [1], respecting vma->pgoff is necessary for users who only want to mmap part of the buffer. Does your DRM driver by any chance need the same fix as the Rockchip one? >> + ret = vm_insert_page(vma, uaddr, pages[i]); >> + if (ret) >> + break; >> + uaddr += PAGE_SIZE; >> + } >> + return ret; >> +} >> + And to save another email: >> + if (WARN_ON(!area || area->pages)) > Is it: if (WARN_ON(!area || !area->pages)) >> + return -ENXIO; You're absolutely right, thanks. I've got a couple more bugfixes in progress too, so I'll try to get an updated branch pushed out soon; I'll hold off posting a v3 to the list until after the upcoming merge window, though. Robin. [1]:http://thread.gmane.org/gmane.linux.kernel/1932343