Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752180AbdCCSkx (ORCPT ); Fri, 3 Mar 2017 13:40:53 -0500 Received: from mail-qk0-f172.google.com ([209.85.220.172]:32797 "EHLO mail-qk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751903AbdCCSkt (ORCPT ); Fri, 3 Mar 2017 13:40:49 -0500 Subject: Re: [RFC PATCH 04/12] staging: android: ion: Call dma_map_sg for syncing and mapping To: Laurent Pinchart , dri-devel@lists.freedesktop.org References: <1488491084-17252-1-git-send-email-labbott@redhat.com> <1488491084-17252-5-git-send-email-labbott@redhat.com> <1842876.9VofhAIJSQ@avalon> Cc: Sumit Semwal , Riley Andrews , arve@android.com, devel@driverdev.osuosl.org, romlem@google.com, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, Mark Brown , Daniel Vetter , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org From: Laura Abbott Message-ID: <579647db-3b4a-37bd-d322-49b4f25bc7bc@redhat.com> Date: Fri, 3 Mar 2017 10:40:27 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <1842876.9VofhAIJSQ@avalon> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7003 Lines: 198 On 03/03/2017 08:37 AM, Laurent Pinchart wrote: > Hi Laura, > > Thank you for the patch. > > On Thursday 02 Mar 2017 13:44:36 Laura Abbott wrote: >> Technically, calling dma_buf_map_attachment should return a buffer >> properly dma_mapped. Add calls to dma_map_sg to begin_cpu_access to >> ensure this happens. As a side effect, this lets Ion buffers take >> advantage of the dma_buf sync ioctls. >> >> Signed-off-by: Laura Abbott >> --- >> drivers/staging/android/ion/ion.c | 101 +++++++++++++++++------------------ >> 1 file changed, 50 insertions(+), 51 deletions(-) >> >> diff --git a/drivers/staging/android/ion/ion.c >> b/drivers/staging/android/ion/ion.c index ce4adac..a931b30 100644 >> --- a/drivers/staging/android/ion/ion.c >> +++ b/drivers/staging/android/ion/ion.c >> @@ -795,10 +795,6 @@ void ion_client_destroy(struct ion_client *client) >> } >> EXPORT_SYMBOL(ion_client_destroy); >> >> -static void ion_buffer_sync_for_device(struct ion_buffer *buffer, >> - struct device *dev, >> - enum dma_data_direction direction); >> - >> static struct sg_table *dup_sg_table(struct sg_table *table) >> { >> struct sg_table *new_table; >> @@ -825,22 +821,43 @@ static struct sg_table *dup_sg_table(struct sg_table >> *table) return new_table; >> } >> >> +static void free_duped_table(struct sg_table *table) >> +{ >> + sg_free_table(table); >> + kfree(table); >> +} >> + >> static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment >> *attachment, enum dma_data_direction direction) >> { >> struct dma_buf *dmabuf = attachment->dmabuf; >> struct ion_buffer *buffer = dmabuf->priv; >> + struct sg_table *table; >> + int ret; >> + >> + /* >> + * TODO: Need to sync wrt CPU or device completely owning? >> + */ >> + >> + table = dup_sg_table(buffer->sg_table); >> >> - ion_buffer_sync_for_device(buffer, attachment->dev, direction); >> - return dup_sg_table(buffer->sg_table); >> + if (!dma_map_sg(attachment->dev, table->sgl, table->nents, >> + direction)){ >> + ret = -ENOMEM; >> + goto err; >> + } >> + >> +err: >> + free_duped_table(table); >> + return ERR_PTR(ret); >> } >> >> static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment, >> struct sg_table *table, >> enum dma_data_direction direction) >> { >> - sg_free_table(table); >> - kfree(table); >> + dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); >> + free_duped_table(table); >> } >> >> void ion_pages_sync_for_device(struct device *dev, struct page *page, >> @@ -864,38 +881,6 @@ struct ion_vma_list { >> struct vm_area_struct *vma; >> }; >> >> -static void ion_buffer_sync_for_device(struct ion_buffer *buffer, >> - struct device *dev, >> - enum dma_data_direction dir) >> -{ >> - struct ion_vma_list *vma_list; >> - int pages = PAGE_ALIGN(buffer->size) / PAGE_SIZE; >> - int i; >> - >> - pr_debug("%s: syncing for device %s\n", __func__, >> - dev ? dev_name(dev) : "null"); >> - >> - if (!ion_buffer_fault_user_mappings(buffer)) >> - return; >> - >> - mutex_lock(&buffer->lock); >> - for (i = 0; i < pages; i++) { >> - struct page *page = buffer->pages[i]; >> - >> - if (ion_buffer_page_is_dirty(page)) >> - ion_pages_sync_for_device(dev, ion_buffer_page(page), >> - PAGE_SIZE, dir); >> - >> - ion_buffer_page_clean(buffer->pages + i); >> - } >> - list_for_each_entry(vma_list, &buffer->vmas, list) { >> - struct vm_area_struct *vma = vma_list->vma; >> - >> - zap_page_range(vma, vma->vm_start, vma->vm_end - vma- >> vm_start); >> - } >> - mutex_unlock(&buffer->lock); >> -} >> - >> static int ion_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) >> { >> struct ion_buffer *buffer = vma->vm_private_data; >> @@ -1014,16 +999,24 @@ static int ion_dma_buf_begin_cpu_access(struct >> dma_buf *dmabuf, struct ion_buffer *buffer = dmabuf->priv; >> void *vaddr; >> >> - if (!buffer->heap->ops->map_kernel) { >> - pr_err("%s: map kernel is not implemented by this heap.\n", >> - __func__); >> - return -ENODEV; >> + /* >> + * TODO: Move this elsewhere because we don't always need a vaddr >> + */ >> + if (buffer->heap->ops->map_kernel) { >> + mutex_lock(&buffer->lock); >> + vaddr = ion_buffer_kmap_get(buffer); >> + mutex_unlock(&buffer->lock); >> } >> >> - mutex_lock(&buffer->lock); >> - vaddr = ion_buffer_kmap_get(buffer); >> - mutex_unlock(&buffer->lock); >> - return PTR_ERR_OR_ZERO(vaddr); >> + /* >> + * Close enough right now? Flag to skip sync? >> + */ >> + if (!dma_map_sg(buffer->dev->dev.this_device, buffer->sg_table->sgl, >> + buffer->sg_table->nents, >> + DMA_BIDIRECTIONAL)) > > Aren't the dma_(un)map_* calls supposed to take a real, physical device as > their first argument ? Beside, this doesn't seem to be the right place to > create the mapping, as you mentioned in the commit message the buffer should > be mapped in the dma_buf map handler. This is something that needs to be > fixed, especially in the light of the comment in ion_buffer_create(): > Yes, this might me a case of me getting the model incorrect again. dma_buf_{begin,end}_cpu_access do not take a device structure and from the comments: /** * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific * preparations. Coherency is only guaranteed in the specified range for the * specified access direction. * @dmabuf: [in] buffer to prepare cpu access for. * @direction: [in] length of range for cpu access. * * Can return negative error values, returns 0 on success. */ If there are no buffer attachments, I guess the notion of 'coherency' doesn't apply here so there is no need to do any kind of syncing/mapping at all vs. trying to find a device out of nowhere. I'll have to go back and re-think aligning sync/begin_cpu_access calls and dma_buf_map calls, or more likely not overthink this. > /* > * this will set up dma addresses for the sglist -- it is not > * technically correct as per the dma api -- a specific > * device isn't really taking ownership here. However, in practice on > * our systems the only dma_address space is physical addresses. > * Additionally, we can't afford the overhead of invalidating every > * allocation via dma_map_sg. The implicit contract here is that > * memory coming from the heaps is ready for dma, ie if it has a > * cached mapping that mapping has been invalidated > */ > > That's a showstopper in my opinion, the DMA address space can't be restricted > to physical addresses, IOMMU have to be supported. > I missed a patch in this series to remove that. If Ion is going to exist outside of staging it should not be making that assumption at all so I want to drop it. Any performance implications should be fixed with the skip sync flag. Thanks, Laura