Re: [PATCH] clk: stm32h7: Add stm32h743 clock driver

From: Stephen Boyd
Date: Fri Apr 07 2017 - 15:52:05 EST


On 04/06, Gabriel Fernandez wrote:
> On 04/06/2017 12:32 AM, Stephen Boyd wrote:
> >On 03/15, gabriel.fernandez@xxxxxx wrote:
> >>diff --git a/Documentation/devicetree/bindings/clock/st,stm32h7-rcc.txt b/Documentation/devicetree/bindings/clock/st,stm32h7-rcc.txt
> >>new file mode 100644
> >>index 0000000..9d4b587
> >>--- /dev/null
> >>+++ b/Documentation/devicetree/bindings/clock/st,stm32h7-rcc.txt
> >>@@ -0,0 +1,152 @@
> >>+
> >>+ rcc: rcc@58024400 {
> >>+ #reset-cells = <1>;
> >>+ #clock-cells = <2>
> >>+ compatible = "st,stm32h743-rcc", "st,stm32-rcc";
> >>+ reg = <0x58024400 0x400>;
> >>+ clocks = <&clk_hse>, <&clk_lse>, <&clk_i2s_ckin>;
> >>+
> >>+ st,syscfg = <&pwrcfg>;
> >>+
> >>+ #address-cells = <1>;
> >>+ #size-cells = <0>;
> >>+
> >>+ vco1@58024430 {
> >>+ #clock-cells = <0>;
> >>+ compatible = "stm32,pll";
> >>+ reg = <0>;
> >reg is super confusing and doesn't match unit address.
> ok i fixed it in the v2
>
> >
> >>+ };
> >Why? Shouldn't we know this from the compatible string how many
> >PLLs there are and where they're located? Export the PLLs through
> >rcc node's clock-cells?
> >
> Because i need to offer the possibility to change the PLL VCO
> frequencies at the start-up of this driver clock.
> The VCO algorithm needs a division factor, a multiplication factor
> and a fractional factor.
> Lot's of solution are possible for one frequency and it's nightmare
> to satisfy the 3 output dividers of the PLL.

Sure, but do we need to configure that on a per-board basis or a
per-SoC basis? If it's just some configuration, I wonder why we
don't put that into the driver and base it off some compatible
string that includes the SoC the device is for.

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