Re: [PATCH v2 4/6] dt: bindings: add mt7621-pll dt binding documentation

Chuanhong Guo
2019-08-17T14:42:26Z

Hi!

On Tue, Aug 13, 2019 at 11:51 PM Rob Herring <robh@kernel.org> wrote:
> [...]
> > +Example:
> > + pll {
> > + compatible = "mediatek,mt7621-pll";
>
> You didn't answer Stephen's question on v1.

I thought he was asking why there's a syscon in compatible string. I
noticed that the syscon in my previous patch is a copy-paste error
from elsewhere and dropped it.

>
> Based on this binding, there is no way to control/program the PLL. Is
> this part of some IP block?

The entire section is called "system control" in datasheet and is
occupied in arch/mips/ralink/mt7621.c [0]
Two clocks provided here is determined by reading some read-only
registers in this part.
There's another register in this section providing clock gates for
every peripherals, but MTK doesn't provide a clock plan in their
datasheet. I can't determine corresponding clock frequencies for every
peripherals, thus unable to write a working clock driver.

>
> > +
> > + #clock-cells = <1>;
> > + clock-output-names = "cpu", "bus";
> > + };
> > --
> > 2.21.0
> >

Regards,
Chuanhong Guo

[0] https://elixir.bootlin.com/linux/latest/source/arch/mips/ralink/mt7621.c#L156