Re: [RFC PATCH 3/3] encoder-tpd12s015: keep the ls_oe_gpio on while the phys_addr is valid

[Hans Verkuil <hverkuil@xs4all.nl>]

On 04/13/2017 10:43 AM, Tomi Valkeinen wrote:
> On 12/04/17 17:04, Hans Verkuil wrote:
> 
>>> So is some other driver supporting this already? Or is the omap4 the
>>> first platform you're trying this on?
>>
>> No, there are quite a few CEC drivers by now, but typically the CEC block is
>> a totally independent IP block with its own power, irq, etc. The omap4 is by far
>> the most complex one to set up with various GPIO pins, interrupts, regulators,
>> etc. to deal with.
>>
>> Normally it takes about 2 days to make a new CEC driver, but the omap4 is much
>> more work :-(
> 
> Ok.
> 
> I mentioned the omapdrm restructuring that we've planned to do, I think
> after that this will be easier to implement in a nice way.
> 
> For now, I think more or less what you have now is an acceptable
> solution. We can hack the tpd12s015 to keep the level shifter always
> enabled, and, afaics, everything else can be handled inside the hdmi4
> driver, right?

Right.

> Generally speaking, what are the "dependencies" for CEC? It needs to
> access EDID? Does CEC care about HPD? Does it care if the cable is
> connected or not? For Panda, the level shifter of tpd12s015 is obviously
> one hard dendency.
> 
> Is there anything else CEC needs to access or control (besides the CEC
> IP itself)?

The CEC framework needs to be informed about the physical address contained
in the EDID (part of the CEA-861 block). And when the HPD goes down it needs
to be informed as well (same call, but with CEC_PHYS_ADDR_INVALID as argument).

And it needs to stay powered up even if the HPD is down.

That's all.

Regards,

	Hans