From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v2 2/4] iommu: Implement common IOMMU ops for DMA mapping Date: Thu, 18 Jun 2015 17:54:29 +0100 Message-ID: <5582F7C5.8060901@arm.com> References: <1434639625.26953.12.camel@mhfsdcap03> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1434639625.26953.12.camel@mhfsdcap03> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Yong Wu Cc: "laurent.pinchart+renesas-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org" , "arnd-r2nGTMty4D4@public.gmane.org" , Catalin Marinas , Will Deacon , "tomasz.figa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "djkurtz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "thunder.leizhen-hv44wF8Li93QT0dZR+AlfA@public.gmane.org" , "yt.shen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org" , "yingjoe.chen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org" , "treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: iommu@lists.linux-foundation.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