[PATCHv2 21/22] drm/bridge: tc358767: add IRQ and HPD support

[Tomi Valkeinen]

On 15/04/2019 13:42, Andrzej Hajda wrote:

> Ok we have here 4 combinations:
> 
> 1. noHPD + eDP.
> 
> 2. noHPD + DP.
> 
> 3. HPD + eDP.
> 
> 4. HPD + DP.
> 
> 
> Which ones do you want to support, disallow. It is not clear to me.

They all should work.

If there is HPD, we use it to return connected/disconnected.

If we don't have HPD:
- If there's a panel (i.e. eDP), we presume that it is always there, as
by definition it can't be disconnected.
- If there's no panel (i.e. DP), we can't know if the cable is connected
or not, so we return unknown. I think this could be improved by trying
to "ping" the monitor with an AUX transaction, but I didn't look at that.

> Moreover what connector_status_unknown should mean here for users?

The the driver does not know if there's a monitor or not.

>> +	if (tc->hpd_num >= 0 && tc->bridge.dev) {
>> +		bool h = val & INT_GPIO_H(tc->hpd_num);
>> +		bool lc = val & INT_GPIO_LC(tc->hpd_num);
>> +
>> +		dev_dbg(tc->dev, "GPIO%d: %s %s\n", tc->hpd_num,
>> +			h ? "H" : "", lc ? "LC" : "");
> 
> 
> What does "h" and "lc" mean?

These are from the func spec. H means high, LC means low-counter. H is
triggered immediately when the HPD line goes high, LC is triggered when
the line has been low for the counter-specified time (the counter is
configured at probe time).

These could be used to implement a more elaborate DP HPD & interrupt
handling, but for the time being the driver just takes them as "HPD may
have changed".

 Tomi

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