Re: [PATCH v7 2/2] dt-bindings: cpufreq: add bindings for MediaTek cpufreq HW

From: Hector Yuan
Date: Wed Sep 23 2020 - 09:10:25 EST

On Tue, 2020-09-22 at 14:28 -0600, Rob Herring wrote:
> On Thu, Sep 10, 2020 at 12:31:02PM +0800, Hector Yuan wrote:
> > From: "Hector.Yuan" <hector.yuan@xxxxxxxxxxxx>
> >
> > Add devicetree bindings for MediaTek HW driver.
> >
> > Signed-off-by: Hector.Yuan <hector.yuan@xxxxxxxxxxxx>
> > ---
> > .../bindings/cpufreq/cpufreq-mediatek-hw.yaml | 141 ++++++++++++++++++++
> > 1 file changed, 141 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-mediatek-hw.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-mediatek-hw.yaml b/Documentation/devicetree/bindings/cpufreq/cpufreq-mediatek-hw.yaml
> > new file mode 100644
> > index 0000000..118a163
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-mediatek-hw.yaml
> > @@ -0,0 +1,141 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/cpufreq/cpufreq-mediatek-hw.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MediaTek's CPUFREQ Bindings
> > +
> > +maintainers:
> > + - Hector Yuan <hector.yuan@xxxxxxxxxxxx>
> > +
> > +description:
> > + CPUFREQ HW is a hardware engine used by MediaTek
> > + SoCs to manage frequency in hardware. It is capable of controlling frequency
> > + for multiple clusters.
> > +
> > +properties:
> > + compatible:
> > + const: "mediatek,cpufreq-hw"
>
> Needs to be SoC specific. This stuff is never constant from one SoC to
> the next. 'cpufreq' is a Linuxism. What's the block called in the
> datasheet? Use that.
>
OK, will use mediatek,sspm-dvfs-mt6779 instead.
> Don't need quotes either.
>
OK, will remove it.
> > +
> > + reg:
> > + minItems: 1
> > + maxItems: 2
> > + description: |
> > + Addresses and sizes for the memory of the HW bases in each frequency domain.
> > +
> > + reg-names:
> > + items:
> > + - const: "freq-domain0"
> > + - const: "freq-domain1"
>
> Kind of pointless to have names based on the index. Drop 'reg-names'.
>
OK, will drop it.
> > + description: |
> > + Frequency domain name. i.e.
> > + "freq-domain0", "freq-domain1".
> > +
> > + "#freq-domain-cells":
> > + const: 1
> > + description: |
> > + Number of cells in a freqency domain specifier.
>
> You don't need this. It's not a common binding that's going to vary.
>
OK, will remove it.
> > +
> > + mtk-freq-domain:
> > + maxItems: 1
> > + description: |
> > + Define this cpu belongs to which frequency domain. i.e.
> > + cpu0-3 belong to frequency domain0,
> > + cpu4-6 belong to frequency domain1.
>
> This property doesn't go in the 'mediatek,cpufreq-hw' node. You would
> need a separate schema. However, I think the easiest thing to do here is
> something like this:
>
> mediatek,freq-domain-0 = <&cpu0>, <&cpu1>;
>
Sorry, may I know the reason and the details about how to separate
schema? Thank you very much.

The numbers of frequency domain may be vary from different projects. If
I do the easier way, I may need to implement extra loop to check how
many frequency domain.
> Or you could just re-use the OPP binding with just 0 entries:
>
> opp-table-0 {
> compatible = "mediatek,hw-operating-points", "operating-points-v2";
> };
> opp-table-1 {
> compatible = "mediatek,hw-operating-points", "operating-points-v2";
> };
>
In previous review stage, already abandon OPP framework in driver code.
Will check with Viresh to see if its OK to add OPP back.
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - reg-names
> > + - "#freq-domain-cells"
> > +
> > +examples:
> > + - |
> > + cpus {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + cpu0: cpu@0 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 0>;
> > + reg = <0x000>;
> > + };
> > +
> > + cpu1: cpu@1 {
>
> Unit address is wrong.
>
OK, will modify to "cpu1 : cpu@100" if we still decide to put
freq_domain in CPU node.
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 0>;
> > + reg = <0x100>;
> > + };
> > +
> > + cpu2: cpu@2 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 0>;
> > + reg = <0x200>;
> > + };
> > +
> > + cpu3: cpu@3 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 0>;
> > + reg = <0x300>;
> > + };
> > +
> > + cpu4: cpu@4 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 1>;
> > + reg = <0x400>;
> > + };
> > +
> > + cpu5: cpu@5 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a55";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 1>;
> > + reg = <0x500>;
> > + };
> > +
> > + cpu6: cpu@6 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a75";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 1>;
> > + reg = <0x600>;
> > + };
> > +
> > + cpu7: cpu@7 {
> > + device_type = "cpu";
> > + compatible = "arm,cortex-a75";
> > + enable-method = "psci";
> > + mtk-freq-domain = <&cpufreq_hw 1>;
> > + reg = <0x700>;
> > + };
> > + };
> > +
> > + /* ... */
> > +
> > + soc {
> > + #address-cells = <2>;
> > + #size-cells = <2>;
> > +
> > + cpufreq_hw: cpufreq@11bc00 {
> > + compatible = "mediatek,cpufreq-hw";
> > + reg = <0 0x11bc10 0 0x8c>,
> > + <0 0x11bca0 0 0x8c>;
> > + reg-names = "freq-domain0", "freq-domain1";
> > + #freq-domain-cells = <1>;
> > + };
> > + };
> > +
> > +
> > +
> > +
> > --
> > 1.7.9.5