linux-kernel - Re: [PATCH v2 1/2] drm: bridge: dw-hdmi: Take input format from plat

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Message-ID: <c57666a2-084d-869d-1ed8-2407b48936e0@baylibre.com>
Date:   Mon, 6 Mar 2017 13:39:56 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Jose Abreu <Jose.Abreu@...opsys.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     dri-devel@...ts.freedesktop.org,
        laurent.pinchart+renesas@...asonboard.com,
        kieran.bingham@...asonboard.com, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drm: bridge: dw-hdmi: Take input format from
 plat_data

On 03/06/2017 01:17 PM, Jose Abreu wrote:
> Hi Neil,
> 
> 
> On 06-03-2017 10:41, Neil Armstrong wrote:
>> On 03/03/2017 06:22 PM, Jose Abreu wrote:
>>> Hi Neil,
>>>
>>>
>>> On 03-03-2017 16:42, Neil Armstrong wrote:
>>>> Sure, I was meaning the *input* format the controller receives from the
>>>> pixel encoder, I'm quite sure the format is strict.
>>>>
>>> Hmm, not quite following you here. As far as the controller goes
>>> it supports the formats I mentioned:
>>>     -    8/10/12/16 bits RGB 4:4:4
>>>     -    8/10/12/16 bits YCbCr 4:4:4
>>>     -    8/10/12 bits YCbCr 4:2:2
>>>     -    8/10/12/16 bits YCbCr 4:2:0
>>>
>>> As for the CSC it supports RGB 4:4:4 to/from YCbCr 4:4:4 or 4:2:2
>>> in every defined color depth.
>>>
>>> So, everything except 4:2:0 (I had to check documentation, I
>>> though that CSC supported less formats).
>>>
>>> Of course this is all limited by the implementation that HW team
>>> decides to choose.
>>>
>>> Best regards,
>>> Jose Miguel Abreu
>>>
>> Hi Jose,
>>
>> Thanks for the clarifications.
>>
>> I will try to add missing V4L formats
>>
>>  - 8/10/12/16 bits RGB 4:4:4
>>
>> MEDIA_BUS_FMT_RGB888_1X24
>> MEDIA_BUS_FMT_RGB101010_1X30 (to be added)
>> MEDIA_BUS_FMT_RGB121212_1X36 (to be added)
>> MEDIA_BUS_FMT_RGB161616_1X48 (to be added)
>>
>>  - 8/10/12/16 bits YCbCr 4:4:4
>>
>> MEDIA_BUS_FMT_YUV8_1X24
>> MEDIA_BUS_FMT_YUV10_1X30
>> MEDIA_BUS_FMT_YUV12_1X36 (to be added)
>> MEDIA_BUS_FMT_YUV16_1X48 (to be added)
>>
>>  - 8/10/12 bits YCbCr 4:2:2
>>
>> MEDIA_BUS_FMT_UYVY8_1X16
>> MEDIA_BUS_FMT_UYVY10_1X20
>> MEDIA_BUS_FMT_UYVY12_1X24
>>
>>  - 8/10/12/16 bits YCbCr 4:2:0
>>
>> Jose, how is supposed to be transmitted 4:2:0 over the controller ?
>>
>> Amlogic uses clock doubling to transmit 4:2:0 in CrYCb format.
>>
>> I assume, the transmission is in YYUYYV format in 2x clock.
> 
> Double rate or half rate? 4:2:0 requires half the bandwidth and
> the horizontal parameters are cut off by half also. I'm not very
> familiar with 4:2:0 but according to spec it shall be Cb[l][n]
> Y[l][n] Y[l][n+1] in one line and then Cr[l][n] Y[l+1][n]
> Y[l+1][n+1] in another line (where "l" is pixel line number and
> "n" is pixel number).

Exact, sorry I mismatch, Amlogic doubles the clock in the encoder and
divides the height by 2 to achieve half bandwidth.

> 
> I've worked with 4:2:0 previously but it was just for a prof of
> concept (I never got to a point where I could submit anything
> standard), maybe someone who has worked with this can expand a
> little bit. Anyone?
> 
>>
>> So the formats should be (aligned on the MEDIA_BUS_FMT_YUYV8_1_5X8) :
>>
>> MEDIA_BUS_FMT_YUYV8_1_1X24 (to be added)
>> MEDIA_BUS_FMT_YUYV10_1_1X30 (to be added)
>> MEDIA_BUS_FMT_YUYV12_1_1X36 (to be added)
>> MEDIA_BUS_FMT_YUYV16_1_1X48 (to be added)
>>
>> to have the following transmissions scheme :
>>
>> uuuuuuuu/yyyyyyyy/yyyyyyyy
>> vvvvvvvv/yyyyyyyy/yyyyyyyy
>>
>> Can you confirm this ?
> 
> Seems fine, chroma in consecutive lines and luma in every line.
>

OK then, thanks, but I mismatched, it should be like the 4:2:2 entries :

MEDIA_BUS_FMT_UYVY8_1_1X24 (to be added)
MEDIA_BUS_FMT_UYVY10_1_1X30 (to be added)
MEDIA_BUS_FMT_UYVY12_1_1X36 (to be added)
MEDIA_BUS_FMT_UYVY16_1_1X48 (to be added)


> Best regards,
> Jose Miguel Abreu
> 
>>
>> Neil
>