[PATCH v3 2/5] dt: bindings: add mt7621-clk device tree binding documentation

[Sergio Paracuellos]

Hi Rob,

Thanks for the review.

On Sat, Nov 21, 2020 at 2:34 PM Rob Herring <robh at kernel.org> wrote:
>
> On Fri, Nov 13, 2020 at 04:46:29PM +0100, Sergio Paracuellos wrote:
> > Adds device tree binding documentation for clocks in the
> > MT7621 SOC.
> >
> > Signed-off-by: Sergio Paracuellos <sergio.paracuellos at gmail.com>
> > ---
> >  .../bindings/clock/mediatek,mt7621-clk.yaml   | 61 +++++++++++++++++++
> >  1 file changed, 61 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > new file mode 100644
> > index 000000000000..363bd9880e29
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > @@ -0,0 +1,61 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/clock/mediatek,mt7621-clk.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MT7621 Clock Device Tree Bindings
> > +
> > +maintainers:
> > +  - Sergio Paracuellos <sergio.paracuellos at gmail.com>
> > +
> > +description: |
> > +  The MT7621 has a PLL controller from where the cpu clock is provided
> > +  as well as derived clocks for the bus and the peripherals. It also
> > +  can gate SoC device clocks.
> > +
> > +  Each clock is assigned an identifier and client nodes use this identifier
> > +  to specify the clock which they consume.
> > +
> > +  All these identifiers could be found in:
> > +  [1]: <include/dt-bindings/clock/mt7621-clk.h>.
> > +
> > +properties:
> > +  compatible:
> > +    const: mediatek,mt7621-clk
> > +
> > +  ralink,sysctl:
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +    description:
> > +      phandle to the syscon which is in the same address area with syscon
> > +      device.
> > +
> > +  "#clock-cells":
> > +    description:
> > +      The first cell indicates the clock gate number, see [1] for available
> > +      clocks.
> > +    const: 1
> > +
> > +  clock-output-names:
> > +    maxItems: 8
> > +
> > +required:
> > +  - compatible
> > +  - ralink,sysctl
> > +  - '#clock-cells'
> > +  - clock-output-names
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/mt7621-clk.h>
> > +
> > +    pll {
> > +      compatible = "mediatek,mt7621-clk";
> > +      ralink,sysctl = <&sysc>;
>
> If this is the only control interface, then make this a child of 'sysc'.
> And use 'reg' if there's a dedicated range of registers.

This is the only one now in the device tree which is still in staging
but there are several places where this sys control registers are
accessed from. In the case of the clocks we need:

#define SYSC_REG_SYSTEM_CONFIG0         0x10
#define SYSC_REG_SYSTEM_CONFIG1         0x14
#define SYSC_REG_CLKCFG0                0x2c
#define SYSC_REG_CLKCFG1                0x30
#define SYSC_REG_CUR_CLK_STS            0x44

where there is not a range as it is but several different registers
from where we need to read or write things. I wrote the driver using
syscon and regmap because I thought in that way it might be more
maintainable but this architecture also has operations to read and
write registers from sysc and not using regmap at all. This operations
are defined in arch/mips/include/asm/mach-ralink/ralink_regs.h. But
because this sysc is currently mapped I cannot request its registers
using reg in the device tree. If you prefer me to avoid the use of
this syscon and regmap and use operations defined in ralink_regs.h,
this will become in a node without "regs" or  "ralink,sysctl"
property:

pll {
    compatible = "mediatek,mt7621-clk";
    #clock-cells = <1>;
    clock-output-names = "xtal", "cpu", "bus",
                      "50m", "125m", "150m",
                       "250m", "270m";
};

What should I do then?

Best regards,
    Sergio Paracuellos

>
> > +      #clock-cells = <1>;
> > +      clock-output-names = "xtal", "cpu", "bus",
> > +                           "50m", "125m", "150m",
> > +                           "250m", "270m";
> > +    };
> > --
> > 2.25.1
> >