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From: Corentin Labbe <clabbe.montjoie@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	hch@lst.de
Subject: Re: DMA mapping fill dma_address to 0
Date: Wed, 28 Apr 2021 12:25:35 +0200	[thread overview]
Message-ID: <YIk4H82yrx+Yzp/U@Red> (raw)
In-Reply-To: <6ce3614e-af79-2a36-de83-6cbb4d9fe9a4@arm.com>

Le Wed, Apr 28, 2021 at 11:06:10AM +0100, Robin Murphy a écrit :
> On 2021-04-28 09:42, Corentin Labbe wrote:
> > Hello
> > 
> > I work on the crypto offloader driver of cortina/gemini SL3516 SoC.
> > I test it by filling a LUKS2 partition.
> > I got a reproductible problem when handling skcipher requests.
> > I use dma_map_sg() and when iterating other the result, sg_dma_address(sg) return 0.
> > But sg_dma_len(sg) is still correct (4096 in my case).
> > 
> > Below is a simplified view of my code:
> > nr_sgs = dma_map_sg(ce->dev, areq->src, sg_nents(areq->src), DMA_TO_DEVICE);
> > (nr_sgs = 1 in my case)
> > sg = areq->src;
> > if (!sg_dma_address(sg))
> > 	FAIL
> 
> What is this check supposed to be for in the first place? 0 is a valid 
> DMA address, because it's also a valid physical address, and I recall 
> RAM at PA 0 on Hikey 960 flushing out some bugs in the past when we 
> tried to use 0 for DMA_MAPPING_ERROR. All the Gemini DTs appear to show 
> RAM starting at PA 0 too, so I'd have to guess that it's simply the case 
> that your DMA buffer happened to end up using that particular page.
> 
> Robin.
> 

Yes, 0 is a valid DMA address.
I just find it by going further and printing mem_map value and testing it against sg_page() return.

So my original problem was not related to this.
Sorry for the noise.
Thanks
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WARNING: multiple messages have this Message-ID (diff)
From: Corentin Labbe <clabbe.montjoie@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: hch@lst.de, m.szyprowski@samsung.com,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: DMA mapping fill dma_address to 0
Date: Wed, 28 Apr 2021 12:25:35 +0200	[thread overview]
Message-ID: <YIk4H82yrx+Yzp/U@Red> (raw)
In-Reply-To: <6ce3614e-af79-2a36-de83-6cbb4d9fe9a4@arm.com>

Le Wed, Apr 28, 2021 at 11:06:10AM +0100, Robin Murphy a écrit :
> On 2021-04-28 09:42, Corentin Labbe wrote:
> > Hello
> > 
> > I work on the crypto offloader driver of cortina/gemini SL3516 SoC.
> > I test it by filling a LUKS2 partition.
> > I got a reproductible problem when handling skcipher requests.
> > I use dma_map_sg() and when iterating other the result, sg_dma_address(sg) return 0.
> > But sg_dma_len(sg) is still correct (4096 in my case).
> > 
> > Below is a simplified view of my code:
> > nr_sgs = dma_map_sg(ce->dev, areq->src, sg_nents(areq->src), DMA_TO_DEVICE);
> > (nr_sgs = 1 in my case)
> > sg = areq->src;
> > if (!sg_dma_address(sg))
> > 	FAIL
> 
> What is this check supposed to be for in the first place? 0 is a valid 
> DMA address, because it's also a valid physical address, and I recall 
> RAM at PA 0 on Hikey 960 flushing out some bugs in the past when we 
> tried to use 0 for DMA_MAPPING_ERROR. All the Gemini DTs appear to show 
> RAM starting at PA 0 too, so I'd have to guess that it's simply the case 
> that your DMA buffer happened to end up using that particular page.
> 
> Robin.
> 

Yes, 0 is a valid DMA address.
I just find it by going further and printing mem_map value and testing it against sg_page() return.

So my original problem was not related to this.
Sorry for the noise.
Thanks

  reply	other threads:[~2021-04-28 10:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-28  8:42 DMA mapping fill dma_address to 0 Corentin Labbe
2021-04-28  8:42 ` Corentin Labbe
2021-04-28 10:06 ` Robin Murphy
2021-04-28 10:06   ` Robin Murphy
2021-04-28 10:25   ` Corentin Labbe [this message]
2021-04-28 10:25     ` Corentin Labbe

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