Re: [PATCH 12/16] gpu: ipu-v3: Fix CSI0 blur in NTSC format

[Steve Longerbeam <steve_longerbeam@mentor.com>]

On 07/15/2016 05:58 AM, Philipp Zabel wrote:
> Am Mittwoch, den 13.07.2016, 16:02 -0700 schrieb Steve Longerbeam:
>> On 07/10/2016 09:33 AM, Steve Longerbeam wrote:
>>>
>>> On 07/08/2016 10:34 AM, Philipp Zabel wrote:
>>>> Am Donnerstag, den 07.07.2016, 16:03 -0700 schrieb Steve Longerbeam:
>>>>> From: Suresh Dhandapani <Suresh.Dhandapani@in.bosch.com>
>>>>>
>>>>> This patch will change the register IPU_CSI0_CCIR_CODE_2 value from
>>>>> 0x40596 to 0x405A6. The change is related to the Start of field 1
>>>>> first blanking line command bit[5-3] for NTSC format only. This
>>>>> change is dependent with ADV chip where the NEWAVMODE is set to 0
>>>>> in register 0x31. Setting NEWAVMODE to "0" in ADV means "EAV/SAV
>>>>> codes generated to suit analog devices encoders".
>>>>>
>>>>> Signed-off-by: Suresh Dhandapani <Suresh.Dhandapani@in.bosch.com>
>>>>> ---
>>>>>    drivers/gpu/ipu-v3/ipu-csi.c | 2 +-
>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/ipu-v3/ipu-csi.c b/drivers/gpu/ipu-v3/ipu-csi.c
>>>>> index 0eac28c..ec81958 100644
>>>>> --- a/drivers/gpu/ipu-v3/ipu-csi.c
>>>>> +++ b/drivers/gpu/ipu-v3/ipu-csi.c
>>>>> @@ -422,7 +422,7 @@ int ipu_csi_init_interface(struct ipu_csi *csi,
>>>>>                  ipu_csi_write(csi, 0xD07DF | CSI_CCIR_ERR_DET_EN,
>>>>>                          CSI_CCIR_CODE_1);
>>>>> -            ipu_csi_write(csi, 0x40596, CSI_CCIR_CODE_2);
>>>>> +            ipu_csi_write(csi, 0x405A6, CSI_CCIR_CODE_2);
>>>>>                ipu_csi_write(csi, 0xFF0000, CSI_CCIR_CODE_3);
>>>>>            } else {
>>>>>                dev_err(csi->ipu->dev,
>>>> This looks like a very hardware specific hack? I'll at least have to
>>>> test if that also works with other analog decoders.
>>> Hi Philipp,
>>>
>>> Yes it's a hack, but it has always been a hack (hardcoded values). And the
>>> reason is simple, nobody AFAIK (including me) understands how to program
>>> these CSI_CCIR_CODE registers, the description in the reference manual is
>>> complete gibberish.
>> Hi Philipp, Ian over at linux-media helped me to understand these registers a
>> little better, although there are still mysteries given the poor documentation.
>> You should have been copied on that linux-media thread.
>>
>>> The reason we made this change is that, in discussions with Analog Devices,
>>> they recommended setting NEWAVMODE, which changes the positions of
>>> the AV codes sent by the ADV7180 on the bt.656 bus. It took Suresh at least
>>> a full day of reverse engineering (Suresh correct me if I am wrong) to hit
>>> on the correct values in these registers to regain stable video after switching
>>> the ADV7180 to NEWAVMODE.
>> So this NEWAVMODE is somehow breaking from the BT.656 standard, which
>> necessitated the change to CSI_CCIR_CODE_2. So NEWAVMODE if enabled in
>> the ADV7180 will break other capture backends that are expecting standard
>> BT.656 SAV/EAV codes. So NEWAVMODE should not be used and I will remove
>> this patch in the next version.
> Ok. To use that mode, first a new v4l2 mbus type and corresponding DT
> bindings would have to be added.

Hmm, do you mean define something like a V4L2_MBUS_BT656_NEWAVMODE,
and then add a new "newavmode" boolean DT binding parsed by
v4l2_of_parse_endpoint()?

I don't know if that would make sense given that this NEWAVMODE is a kind
of hack of the BT.656 standard, only used by Analog Devices 
encoders/decoders.

Although there a _lot_ of AD encoder/decoder chips (and subdev drivers 
written for
them), so maybe it would make sense to do this.

Adding Hans.

Steve