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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Ricardo Ribalda <ribalda@chromium.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Media Mailing List <linux-media@vger.kernel.org>,
	Tomasz Figa <tfiga@chromium.org>,
	Sergey Senozhatsky <senozhatsky@google.com>
Subject: Re: [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API
Date: Thu, 26 Nov 2020 20:44:50 +0900	[thread overview]
Message-ID: <20201126114450.GB3723071@google.com> (raw)
In-Reply-To: <20201125221917.150463-1-ribalda@chromium.org>

On (20/11/25 23:19), Ricardo Ribalda wrote:
[..]
> +	if (uvc_urb->pages)
> +		dma_sync_sgtable_for_device(stream_to_dmadev(uvc_urb->stream),
> +					    &uvc_urb->sgt, DMA_FROM_DEVICE);

[..]

> +	if (uvc_urb->pages)
> +		dma_sync_sgtable_for_cpu(stream_to_dmadev(stream),
> +					 &uvc_urb->sgt, DMA_FROM_DEVICE);

[..]

> +	uvc_urb->pages = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
> +						 &uvc_urb->dma,
> +						 gfp_flags | __GFP_NOWARN, 0);

Do we need to pass __GFP_NOWARN? It seems that

dma_alloc_noncontiguous()
  __iommu_dma_alloc_noncontiguous()
    __iommu_dma_alloc_pages()

does this internally.

> +	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);

This is not related to Ricardo's patch, just a side note:

  I think VM_DMA_COHERENT needs to be renamed. I found it a bit confusing
  to see DMA_COHERENT mapping being dma_sync-ed. It turned out that the
  flag has different meaning.

	-ss

WARNING: multiple messages have this Message-ID (diff)
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Ricardo Ribalda <ribalda@chromium.org>
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>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API
Date: Thu, 26 Nov 2020 20:44:50 +0900	[thread overview]
Message-ID: <20201126114450.GB3723071@google.com> (raw)
In-Reply-To: <20201125221917.150463-1-ribalda@chromium.org>

On (20/11/25 23:19), Ricardo Ribalda wrote:
[..]
> +	if (uvc_urb->pages)
> +		dma_sync_sgtable_for_device(stream_to_dmadev(uvc_urb->stream),
> +					    &uvc_urb->sgt, DMA_FROM_DEVICE);

[..]

> +	if (uvc_urb->pages)
> +		dma_sync_sgtable_for_cpu(stream_to_dmadev(stream),
> +					 &uvc_urb->sgt, DMA_FROM_DEVICE);

[..]

> +	uvc_urb->pages = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
> +						 &uvc_urb->dma,
> +						 gfp_flags | __GFP_NOWARN, 0);

Do we need to pass __GFP_NOWARN? It seems that

dma_alloc_noncontiguous()
  __iommu_dma_alloc_noncontiguous()
    __iommu_dma_alloc_pages()

does this internally.

> +	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);

This is not related to Ricardo's patch, just a side note:

  I think VM_DMA_COHERENT needs to be renamed. I found it a bit confusing
  to see DMA_COHERENT mapping being dma_sync-ed. It turned out that the
  flag has different meaning.

	-ss
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-11-26 11:44 UTC|newest]

Thread overview: 45+ 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
2020-11-25 22:19 ` Ricardo Ribalda
2020-11-26 11:44 ` Sergey Senozhatsky [this message]
2020-11-26 11:44   ` Sergey Senozhatsky
2020-11-30  8:31   ` Christoph Hellwig
2020-11-30  8:31     ` Christoph Hellwig
2020-11-30  8:34 ` Christoph Hellwig
2020-11-30  8:34   ` Christoph Hellwig
2020-11-30 10:49   ` Ricardo Ribalda
2020-11-30 10:49     ` Ricardo Ribalda
2020-12-01  3:36   ` Sergey Senozhatsky
2020-12-01  3:36     ` Sergey Senozhatsky
2020-12-01 14:49     ` Christoph Hellwig
2020-12-01 14:49       ` Christoph Hellwig
2020-12-08  4:54       ` Tomasz Figa
2020-12-08  4:54         ` Tomasz Figa
2020-12-08  6:45         ` Sergey Senozhatsky via iommu
2020-12-08  7:13         ` Sergey Senozhatsky
2020-12-08  7:13           ` Sergey Senozhatsky
2020-12-09 11:16           ` . Christoph Hellwig
2020-12-09 11:16             ` . Christoph Hellwig
2021-01-07 14:14             ` Ricardo Ribalda
2021-01-07 14:14               ` Ricardo Ribalda
2021-01-11  8:36               ` . Christoph Hellwig
2021-01-11  8:36                 ` . Christoph Hellwig
2021-01-15 13:08                 ` Ricardo Ribalda
2021-01-15 13:08                   ` Ricardo Ribalda
2021-01-20 17:17                   ` . Christoph Hellwig
2021-01-20 17:17                     ` . Christoph Hellwig
2021-01-26 17:06                   ` . Christoph Hellwig
2021-01-26 17:06                     ` . Christoph Hellwig
2021-01-26 23:29                     ` Ricardo Ribalda
2021-01-26 23:29                       ` Ricardo Ribalda
2021-01-27 15:56                       ` . Christoph Hellwig
2021-01-27 15:56                         ` . Christoph Hellwig
2021-01-27 21:35                         ` Ricardo Ribalda
2021-01-27 21:35                           ` Ricardo Ribalda
2021-01-28  7:57                           ` . Christoph Hellwig
2021-01-28  7:57                             ` . Christoph Hellwig
2020-12-09 11:12         ` Christoph Hellwig
2020-12-09 11:12           ` Christoph Hellwig
2020-12-09 13:05           ` Robin Murphy
2020-12-09 13:05             ` Robin Murphy
2020-12-10  5:08             ` Tomasz Figa
2020-12-10  5:08               ` Tomasz Figa

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