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SubjectRe: [PATCH 4/4] arm64: dts: rockchip: add video codec for rk3399
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Hello Ezequiel

Sent from my iPad

> On Jan 7, 2019, at 1:21 AM, Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> wrote:
>
>> On Sun, 6 Jan 2019 at 13:16, Ayaka <ayaka@soulik.info> wrote:
>>
>>
>>
>> Sent from my iPad
>>
>>> On Jan 7, 2019, at 12:04 AM, Ezequiel Garcia <ezequiel@collabora.com> wrote:
>>>
>>> On Sun, 2019-01-06 at 23:05 +0800, Ayaka wrote:
>>>>> On Jan 6, 2019, at 10:22 PM, Ezequiel Garcia <ezequiel@collabora.com> wrote:
>>>>>
>>>>> Hi Randy,
>>>>>
>>>>> Thanks a lot for this patches. They are really useful
>>>>> to provide more insight into the VPU hardware.
>>>>>
>>>>> This change will make the vpu encoder and vpu decoder
>>>>> completely independent, can they really work in parallel?
>>>> As I said it depends on the platform, but with this patch, the user space would think they can work at the same time.
>>>
>>>
>>> I think there is some confusion.
>>>
>>> The devicetree is one thing: it is a hardware representation,
>>> a way to describe the hardware, for the kernel/bootloader to
>>> parse.
>>>
>>> The userspace view will depend on the driver implementation.
>>>
>>> The current devicetree and driver (without your patches),
>>> model the VPU as a single piece of hardware, exposing a decoder
>>> and an encoder.
>>>
>>> The V4L driver will then create two video devices, i.e. /dev/videoX
>>> and /dev/videoY. So userspace sees an independent view of the
>>> devices.
>>>
>> I knew that, the problem is that the driver should not always create a decoder and encoder pair, they may not exist at some platforms, even some platforms doesn’t have a encoder. You may have a look on the rk3328 I post on the first email as example.
>
> That is correct. But that still doesn't tackle my question: is the
> hardware able to run a decoding and an encoding job in parallel?
>
For rk3328, yes, you see I didn’t draw them in the same box.
> If not, then it's wrong to describe them as independent entities.
>
>>> However, they are internally connected, and thus we can
>>> easily avoid two jobs running in parallel.
>>>
>> That is what the mpp service did in my patches, handing the relationship between each devices. And it is not a easy work, maybe a 4k decoder would be blocked by another high frame rate encoding work or another decoder session. The vendor kernel have more worry about this, but not in this version.
>
> Right. That is one way to design it. Another way is having a single
> devicetree node for the VPU encoder/decoder "complex".
No, you can’t assume which one is in the combo group, it can be various. you see, in the rk3328, the vdpu is paired with an avs+ decoder. That is why I use a virtual device standing for scheduler.
>
> Thanks for the input!
> --
> Ezequiel García, VanguardiaSur
> www.vanguardiasur.com.ar

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