Re: [PATCH v2 11/14] v4l: vsp1: Add support for header display lists in continuous mode

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

On 01/08/17 19:47, Laurent Pinchart wrote:
> Hi Kieran,
> 
> On Tuesday 01 Aug 2017 18:35:48 Kieran Bingham wrote:
>> On 26/06/17 19:12, Laurent Pinchart wrote:
>>> The VSP supports both header and headerless display lists. The latter is
>>> easier to use when the VSP feeds data directly to the DU in continuous
>>> mode, and the driver thus uses headerless display lists for DU operation
>>> and header display lists otherwise.
>>>
>>> Headerless display lists are only available on WPF.0. This has never
>>> been an issue so far, as only WPF.0 is connected to the DU. However, on
>>> H3 ES2.0, the VSP-DL instance has both WPF.0 and WPF.1 connected to the
>>> DU. We thus can't use headerless display lists unconditionally for DU
>>> operation.
>>
>> Would it be crazy to suggest we drop headerless display lists?
>>
>> If we must support header display lists in continuous mode - Rather than
>> having 2 cases for continuous modes to support (having to support
>> headerless, on WPF.0, and header on WPF.1) if we just use your header loop
>> trick - would that simplify our code maintenance?
>>
>> (We can always remove headerless support later if you agree, this is more of
>> an idea at the moment)
> 
> I had the exact same thought, but I believe we should wait a few kernel 
> releases to see if the next code is stable before removing the old one. I have 
> a debug patch that forces usage of header display lists unconditionally, and 
> I'll try to develop a few additional stress-tests for that.

Sounds like a good plan.

--
Kieran
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