[linux-sunxi] Re: [PATCH 4/4] simplefb: add clock handling code

[Michal Suchanek]

Hello,

On 27 August 2014 17:42, Maxime Ripard <maxime.ripard at free-electrons.com> wrote:
> On Wed, Aug 27, 2014 at 11:52:48AM +0200, Thierry Reding wrote:
>> On Wed, Aug 27, 2014 at 10:45:26AM +0200, Maxime Ripard wrote:
>> > On Wed, Aug 27, 2014 at 08:54:41AM +0200, Thierry Reding wrote:
>> > > On Tue, Aug 26, 2014 at 11:02:48PM +0200, Maxime Ripard wrote:
>> > > > On Tue, Aug 26, 2014 at 04:35:51PM +0200, Thierry Reding wrote:
>> [...]
>> > > > > > Mike Turquette repeatedly said that he was against such a DT property:
>> > > > > > https://lkml.org/lkml/2014/5/12/693
>> > > > >
>> > > > > Mike says in that email that he's opposing the addition of a property
>> > > > > for clocks that is the equivalent of regulator-always-on. That's not
>> > > > > what this is about. If at all it'd be a property to mark a clock that
>> > > > > should not be disabled by default because it's essential.
>> > > >
>> > > > It's just semantic. How is "a clock that should not be disabled by
>> > > > default because it's essential" not a clock that stays always on?
>> > >
>> > > Because a clock that should not be disabled by default can be turned off
>> > > when appropriate. A clock that is always on can't be turned off.
>> >
>> > If a clock is essential, then it should never be disabled. Or we don't
>> > share the same meaning of essential.
>>
>> Essential for the particular use-case.
>
> So, how would the clock driver would know about which use case we're
> in? How would it know about which display engine is currently running?
> How would it know about which video output is being set?
>
> Currently, we have two separate display engines, which can each output
> either to 4 different outputs (HDMI, RGB/LVDS, 2 DSI). Each and every
> one of these combinations would require different clocks. What clocks
> will we put in the driver? All of them?
>

since simplefb cannot be extended how about adding, say, dtfb which
claims the resources from dt and then instantiates a simplefb once the
resources are claimed? That is have a dtfb which has the clocks
assigned and has simplefb as child dt node.

Thanks

Michal