From: Ricardo Ribalda <ribalda@chromium.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Sergey Senozhatsky <senozhatsky@google.com>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API
Date: Mon, 30 Nov 2020 11:49:09 +0100 [thread overview]
Message-ID: <CANiDSCtE3TqOK0cbw0SJ3LfqCsM3B8AFjBomfj4hcftyHXYXLg@mail.gmail.com> (raw)
In-Reply-To: <20201130083410.GD32234@lst.de>
Hi Christoph
On Mon, Nov 30, 2020 at 9:34 AM Christoph Hellwig <hch@lst.de> wrote:
>
> > +#ifndef CONFIG_DMA_NONCOHERENT
>
> I think you need to drop this ifdef. This code should work just fine
> on noncoherent mips and sh platforms.
>
> > + 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;
> > + }
> > +
> > + if (sg_alloc_table_from_pages(&uvc_urb->sgt, uvc_urb->pages,
> > + PAGE_ALIGN(stream->urb_size) >> PAGE_SHIFT, 0,
> > + stream->urb_size, GFP_KERNEL)) {
> > + vunmap(uvc_urb->buffer);
> > + dma_free_noncontiguous(dma_dev, stream->urb_size,
> > + uvc_urb->pages, uvc_urb->dma);
> > + return false;
> > + }
> > +
> > + return true;
> > +}
>
> I wonder if we should lift this into a helper. On the one hand I had
> proliferating struct scatterlist usage, on the other hand it is all over
> the media and drm code anyway, and duplicating this doesn't help anyone.
>
> Possibly including the fallback to the coherent allocating.
Probably Sergey has best opinion of this than mine. I only had to look
into one driver, he has been working with the vb2, which uses the API
much more.
--
Ricardo Ribalda
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iommu@lists.linux-foundation.org
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next prev parent reply other threads:[~2020-11-30 10:49 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 22:19 [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API Ricardo Ribalda
2020-11-26 11:44 ` Sergey Senozhatsky
2020-11-30 8:31 ` Christoph Hellwig
2020-11-30 8:34 ` Christoph Hellwig
2020-11-30 10:49 ` Ricardo Ribalda [this message]
2020-12-01 3:36 ` Sergey Senozhatsky
2020-12-01 14:49 ` Christoph Hellwig
2020-12-08 4:54 ` Tomasz Figa
2020-12-08 6:45 ` Sergey Senozhatsky via iommu
2020-12-08 7:13 ` Sergey Senozhatsky
2020-12-09 11:16 ` . Christoph Hellwig
2021-01-07 14:14 ` Ricardo Ribalda
2021-01-11 8:36 ` . Christoph Hellwig
2021-01-15 13:08 ` Ricardo Ribalda
2021-01-20 17:17 ` . Christoph Hellwig
2021-01-26 17:06 ` . Christoph Hellwig
2021-01-26 23:29 ` Ricardo Ribalda
2021-01-27 15:56 ` . Christoph Hellwig
2021-01-27 21:35 ` Ricardo Ribalda
2021-01-28 7:57 ` . Christoph Hellwig
2020-12-09 11:12 ` Christoph Hellwig
2020-12-09 13:05 ` Robin Murphy
2020-12-10 5:08 ` Tomasz Figa
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