From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B6DBC63798 for ; Tue, 24 Nov 2020 16:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0176C20897 for ; Tue, 24 Nov 2020 16:29:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390483AbgKXQ31 (ORCPT ); Tue, 24 Nov 2020 11:29:27 -0500 Received: from foss.arm.com ([217.140.110.172]:42176 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389808AbgKXQ30 (ORCPT ); Tue, 24 Nov 2020 11:29:26 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A539E1396; Tue, 24 Nov 2020 08:29:25 -0800 (PST) Received: from [10.57.59.159] (unknown [10.57.59.159]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2DCF93F71F; Tue, 24 Nov 2020 08:29:22 -0800 (PST) Subject: Re: [PATCH 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API To: Ricardo Ribalda , Christoph Hellwig , Mauro Carvalho Chehab , Marek Szyprowski , IOMMU DRIVERS , Joerg Roedel , Linux Doc Mailing List , Linux Kernel Mailing List , Linux Media Mailing List , Tomasz Figa , Sergey Senozhatsky References: <20201124153845.132207-1-ribalda@chromium.org> <20201124153845.132207-5-ribalda@chromium.org> From: Robin Murphy Message-ID: Date: Tue, 24 Nov 2020 16:29:20 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201124153845.132207-5-ribalda@chromium.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 2020-11-24 15:38, Ricardo Ribalda wrote: > On architectures where the is no coherent caching such as ARM use the > dma_alloc_noncontiguos API and handle manually the cache flushing using > dma_sync_single(). > > With this patch on the affected architectures we can measure up to 20x > performance improvement in uvc_video_copy_data_work(). > > Signed-off-by: Ricardo Ribalda > --- > drivers/media/usb/uvc/uvc_video.c | 74 ++++++++++++++++++++++++++----- > drivers/media/usb/uvc/uvcvideo.h | 1 + > 2 files changed, 63 insertions(+), 12 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > index a6a441d92b94..9e90b261428a 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -1490,6 +1490,11 @@ static void uvc_video_encode_bulk(struct uvc_urb *uvc_urb, > urb->transfer_buffer_length = stream->urb_size - len; > } > > +static inline struct device *stream_to_dmadev(struct uvc_streaming *stream) > +{ > + return stream->dev->udev->bus->controller->parent; > +} > + > static void uvc_video_complete(struct urb *urb) > { > struct uvc_urb *uvc_urb = urb->context; > @@ -1539,6 +1544,11 @@ static void uvc_video_complete(struct urb *urb) > * Process the URB headers, and optionally queue expensive memcpy tasks > * to be deferred to a work queue. > */ > + if (uvc_urb->pages) > + dma_sync_single_for_cpu(stream_to_dmadev(stream), > + urb->transfer_dma, > + urb->transfer_buffer_length, > + DMA_FROM_DEVICE); This doesn't work. Even in iommu-dma, the streaming API still expects to work on physically-contiguous memory that could have been passed to dma_map_single() in the first place. As-is, this will invalidate transfer_buffer_length bytes from the start of the *first* physical page, and thus destroy random other data if lines from subsequent unrelated pages are dirty in caches. The only feasible way to do a DMA sync on disjoint pages in a single call is with a scatterlist. Robin. > stream->decode(uvc_urb, buf, buf_meta); > > /* If no async work is needed, resubmit the URB immediately. */ > @@ -1566,8 +1576,15 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream) > continue; > > #ifndef CONFIG_DMA_NONCOHERENT > - usb_free_coherent(stream->dev->udev, stream->urb_size, > - uvc_urb->buffer, uvc_urb->dma); > + if (uvc_urb->pages) { > + vunmap(uvc_urb->buffer); > + dma_free_noncontiguous(stream_to_dmadev(stream), > + stream->urb_size, > + uvc_urb->pages, uvc_urb->dma); > + } else { > + usb_free_coherent(stream->dev->udev, stream->urb_size, > + uvc_urb->buffer, uvc_urb->dma); > + } > #else > kfree(uvc_urb->buffer); > #endif > @@ -1577,6 +1594,47 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream) > stream->urb_size = 0; > } > > +#ifndef CONFIG_DMA_NONCOHERENT > +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, > + struct uvc_urb *uvc_urb, gfp_t gfp_flags) > +{ > + struct device *dma_dev = dma_dev = stream_to_dmadev(stream); > + > + if (!dma_can_alloc_noncontiguous(dma_dev)) { > + uvc_urb->buffer = usb_alloc_coherent(stream->dev->udev, > + stream->urb_size, > + gfp_flags | __GFP_NOWARN, > + &uvc_urb->dma); > + return uvc_urb->buffer != NULL; > + } > + > + uvc_urb->pages = dma_alloc_noncontiguous(dma_dev, stream->urb_size, > + &uvc_urb->dma, > + gfp_flags | __GFP_NOWARN, 0); > + if (!uvc_urb->pages) > + return false; > + > + uvc_urb->buffer = vmap(uvc_urb->pages, > + PAGE_ALIGN(stream->urb_size) >> PAGE_SHIFT, > + VM_DMA_COHERENT, PAGE_KERNEL); > + if (!uvc_urb->buffer) { > + dma_free_noncontiguous(dma_dev, stream->urb_size, > + uvc_urb->pages, uvc_urb->dma); > + return false; > + } > + > + return true; > +} > +#else > +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, > + struct uvc_urb *uvc_urb, gfp_t gfp_flags) > +{ > + uvc_urb->buffer = kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); > + > + return uvc_urb->buffer != NULL; > +} > +#endif > + > /* > * Allocate transfer buffers. This function can be called with buffers > * already allocated when resuming from suspend, in which case it will > @@ -1607,19 +1665,11 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, > > /* Retry allocations until one succeed. */ > for (; npackets > 1; npackets /= 2) { > + stream->urb_size = psize * npackets; > for (i = 0; i < UVC_URBS; ++i) { > struct uvc_urb *uvc_urb = &stream->uvc_urb[i]; > > - stream->urb_size = psize * npackets; > -#ifndef CONFIG_DMA_NONCOHERENT > - uvc_urb->buffer = usb_alloc_coherent( > - stream->dev->udev, stream->urb_size, > - gfp_flags | __GFP_NOWARN, &uvc_urb->dma); > -#else > - uvc_urb->buffer = > - kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); > -#endif > - if (!uvc_urb->buffer) { > + if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) { > uvc_free_urb_buffers(stream); > break; > } > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > index a3dfacf069c4..3e3ef1f1daa5 100644 > --- a/drivers/media/usb/uvc/uvcvideo.h > +++ b/drivers/media/usb/uvc/uvcvideo.h > @@ -532,6 +532,7 @@ struct uvc_urb { > > char *buffer; > dma_addr_t dma; > + struct page **pages; > > unsigned int async_operations; > struct uvc_copy_op copy_operations[UVC_MAX_PACKETS]; >