Hi Laurent / Guennadi,
On Sat, Aug 10, 2013 at 1:06 AM, Su Jiaquan <jiaquan.lnx@xxxxxxxxx> wrote:
> Hi Laurent / Guennadi,
>
> On Fri, Aug 9, 2013 at 5:12 AM, Laurent Pinchart
> <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>> Hi,
>>
>> On Tuesday 06 August 2013 17:18:14 Su Jiaquan wrote:
>>> Hi Guennadi,
>>>
>>> Thanks for the reply! Please see my description inline.
>>>
>>> On Mon, Aug 5, 2013 at 5:02 AM, Guennadi Liakhovetski wrote:
>>> > On Sun, 4 Aug 2013, Su Jiaquan wrote:
>>> >> Hi,
>>> >>
>>> >> I know the title looks crazy, but here is our problem:
>>> >>
>>> >> In our SoC based ISP, the hardware can be divide to several blocks.
>>> >> Some blocks can do color space conversion(raw to YUV interleave/planar),
>>> >> others can do the pixel re-order(interleave/planar/semi-planar
>>> >> conversion, UV planar switch). We use one subdev to describe each of
>>> >> them, then came the problem: How can we express the planar formats with
>>> >> mediabus format code?
>>> >
>>> > Could you please explain more exactly what you mean? How are those your
>>> > blocks connected? How do they exchange data? If they exchange data over a
>>> > serial bus, then I don't think planar formats make sense, right? Or do
>>> > your blocks really output planes one after another, reordering data
>>> > internally? That would be odd... If OTOH your blocks output data to RAM,
>>> > and the next block takes data from there, then you use V4L2_PIX_FMT_*
>>> > formats to describe them and any further processing block should be a
>>> > mem2mem device. Wouldn't this work?
>>>
>>> These two hardware blocks are both located inside of ISP, and is connected
>>> by a hardware data bus.
>>>
>>> Actually, there are three blocks inside ISP: One is close to sensor, and can
>>> do color space conversion(RGB->YUV), we call it IPC; The other two are at
>>> back end, which are basically DMA Engine, and they are identical. When data
>>> flow out of IPC, it can go into each one of these DMA Engines and finally
>>> into RAM. Whether the DMA Engine is turned on/off and the output format can
>>> be controlled independently. Since they are DMA Engines, they have some
>>> basic pixel reordering ability(i.e. interleave->planar/semi-planar).
>>>
>>> In our H/W design, when we want to get YUV semi-planar format, the IPC
>>> output should be configured to interleave, and the DMA engine will do the
>>> interleave->semi-planar job. If we want planar / interleave format, the IPC
>>> will output planar format directly, DMA engine simply send the data to RAM,
>>> and don't do any re-order. So in the planar output case, media-bus formats
>>> can't express the format of the data between IPC and DMA Engine, that's the
>>> problem we meet.
>>
>> If the format between the two subdevs is really planar, I don't see any
>> problem defining a media bus pixel code for it. You will have to properly
>> document the format of course.
>>
>> I'm a bit surprised that the IPC could output planar data. It would need to
>> buffer a whole image to do so, do you need to give it a temporary system RAM
>> buffer ?
>>
>>> We want to adopt a formal solution before we send our patch to the
>>> community, that's where our headache comes.
>>
>> --
>> Regards,
>>
>> Laurent Pinchart
>>
>
> Thanks for the reply!
>
> Actually, we don't need to buffer the frame inside IPC, there are
> three channels in the data bus. When transfering interleave format,
> only one channel is used, for planar formats, three channels send one
> planar each, and to difference address(Let me confirm this with our
> H/W team and get back to you later). So the planars is not sent one
> after an other, but in parallel.
>
> This may be a bit different from the planar formats as people think it
> should be. Can we use planar format to describe it? Since this won't
> cause any misunderstanding given it's used in this special case.
> Please advice.
>
> Thanks a lot!
>
> Jiaquan
I have to say I'm sorry for the wrong information. I just double
checked with hardware team, and turns out there is only one channel
for the data bus between IPC and ispdma.
If ispdma output planar format, the data format between IPC and ispdma
should be configured to a special format, that is not the same with
any know media-bus format.
So I think what we need is to define vendor-specific media-bus code.
Since others any want to do the same thing, shall we define a base
address for the vendor specific formats? For example:
enum v4l2_mbus_pixelcode {
V4L2_MBUS_FMT_FIXED = 0x0001,
...
/* JPEG compressed formats - next is 0x4002 */
V4L2_MBUS_FMT_JPEG_1X8 = 0x4001,
+ V4L2_MBUS_FMT_PRIVATE_BASE = 0xF001,
};
If you are OK with this, I'll prepare a patch to add it
Thanks!
Jiaquan
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