Re: PCIe P2P access to GPU memory

From: "Christian König" <christian.koenig@amd.com>
To: Dirk Eibach <dirk.eibach@googlemail.com>, Dieter@nuetzel-hh.de
Cc: dri-devel@lists.freedesktop.org
Subject: Re: PCIe P2P access to GPU memory
Date: Mon, 1 Oct 2018 20:12:52 +0200	[thread overview]
Message-ID: <2eda0bdf-c532-9ef4-c66a-d85108092a20@amd.com> (raw)
In-Reply-To: <CANVMifLdnP+jfb=CBobFqTpK01X_=f68Nc40SUwnN0AcpzxKCA@mail.gmail.com>

Hi Dirk,

> Any ideas?
Could be anything. Most likely cause is that some function things the 
two device can't communicate directly with each other.

Please provide a full dmesg and "lspci -t -nn -v" as attachment and note 
which devices should communicate with which.

I'm currently on vacation so it could take a while till I have time to 
look deeper into this.

Christian.

Am 01.10.2018 um 15:07 schrieb Dirk Eibach:
> Hi Christian,
>
> I took the repository Dieter suggested and gave it a spin. I am not
> sure, if I got the API right.
>
> In userspace I create a bo and get a fd.
> bo = gbm_bo_create(gbm, w, h, GBM_FORMAT_ARGB8888, GBM_BO_USE_LINEAR);
> dmabuf_fd = gbm_bo_get_fd(bo);
>
> Then I pass the fd to the grabber driver. There I get a sgt, that I
> want to pass to the DMA-machine.
> struct dma_buf_attach_info dma_buf_attach_info = {
>      .dev = &engine->xdev->pdev->dev,
>      .peer2peer = true,
> };
> dma_buf = dma_buf_get(xdma_dma_buf_ioctl.dma_buf_fd);
> dma_buf_attach_info.dmabuf = dma_buf;
> dma_buf_attachment = dma_buf_attach(&dma_buf_attach_info);
> sgt = dma_buf_map_attachment(dma_buf_attachment, DMA_TO_DEVICE);
>
> But the addresses in the sgt do not look like PCIe addresses at at all.
>
> Any ideas?
>
> Cheers
> Dirk
> Am Sa., 29. Sep. 2018 um 11:53 Uhr schrieb Dieter Nützel <Dieter@nuetzel-hh.de>:
>> Hello Dirk,
>>
>> I think Christian is talking about this branch:
>>
>> https://cgit.freedesktop.org/~deathsimple/linux/log/?h=p2p
>>
>> His 'home' is, here:
>> https://cgit.freedesktop.org/~deathsimple/linux/
>>
>> Happy hacking! ;-)
>>
>> Dieter
>>
>> Am 29.09.2018 10:17, schrieb Dirk Eibach:
>>>> This is work in progress.
>>>>
>>>> I published patches to enable DMA_buf P2P a few months ago, but now
>>>> I'm waiting for the PCI subsystem to pick up core support for this.
>>> Great news! Can you give me a link to this series so I can already have
>>> a look?
>>>
>>>> I can prepare you a branch based on current upstream kernel next week
>>>> if you want to test this.
>>> That would be awesome, thanks.
>>>
>>> Cheers
>>> Dirk
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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