[PATCH v2 3/5] media: mediatek: vcodec: Read HW active status from clock

[Stephen Boyd]

Quoting AngeloGioacchino Del Regno (2023-06-14 01:13:43)
> Il 12/06/23 21:19, Stephen Boyd ha scritto:
> > Quoting AngeloGioacchino Del Regno (2023-06-09 00:42:13)
> >> Il 09/06/23 01:56, Stephen Boyd ha scritto:
> >>> Quoting AngeloGioacchino Del Regno (2023-06-08 02:01:58)
> >>>> Il 08/06/23 10:12, Chen-Yu Tsai ha scritto:
> >>>>> On Thu, Jun 8, 2023 at 4:57 AM Nícolas F. R. A. Prado
> >>>>> <nfraprado at collabora.com> wrote:
> >>
> >> The firmware gives an indication of "boot done", but that's for the "core" part
> >> of the vcodec... then it manages this clock internally to enable/disable the
> >> "compute" IP of the decoder.
> >>
> >> As far as I know (and I've been researching about this) the firmware will not
> >> give any "decoder powered, clocked - ready to get data" indication, and the
> >> only way that we have to judge whether it is in this specific state or not is
> >> to check if the "VDEC_ACTIVE" clock got enabled by the firmware.
> > 
> > Is Linux ever going to use clk consumer APIs like clk_enable/clk_disable
> > on this VDEC_ACTIVE clk? If the answer is no, then there isn't any
> > reason to put it in the clk framework, and probably syscon is the way to
> > go for now.
> > 
> 
> Not for the current platform, but that may change in future SoCs... we're not sure.

If you're not using the clk consumer APIs then it shouldn't be a clk.

> 
> > Another approach could be to wait for some amount of time after telling
> > firmware to power up and assume the hardware is active.
> > 
> 
> That would be highly error prone though. Expecting that the HW is alive means that
> we're 100% sure that both firmware and driver are doing the right thing at every
> moment, which is something that we'd like to assume but, realistically, for safety
> reasons we just don't.
> 
> Should we anyway go for a syscon *now* and then change it to a clock later, if any
> new platform needs this as a clock?

Yeah. Or implement this as a power domain and have it read the register
directly waiting to return from the power_on()?