Date:   Thu, 17 Nov 2022 18:37:59 +0000
From:   "Larson, Bradley" <Bradley.Larson@....com>
To:     Rob Herring <robh@...nel.org>, Brad Larson <brad@...sando.io>
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Subject: Re: [PATCH v8 06/17] dt-bindings: mfd: amd,pensando-elbasr: Add AMD
 Pensando Elba System Resource chip

[AMD Official Use Only - General]

Hi Rob and Krzysztof,

> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/mfd/amd,pensando-elbasr.yaml
> > ...
> > > > +
> > > > +title: AMD Pensando Elba SoC Resource Controller
> > > > +
> > > > +description: |
> > > > +  AMD Pensando Elba SoC Resource Controller functions are
> > > > +  accessed with four chip-selects.  Reset control is on CS0.
> > >
> > > One device with 4 chip-selects? Then I'd expect 'reg = <0 1 2 3>;'
> > >
> > > Hard to say more because I don't have the whole thread nor remember what
> > > exactly we discussed before. That was 100s of bindings ago...
> >
> > I agree and the example for v7 had all 4 chip-selects shown.
>
> That is not what I said. Look at 'reg' above again. You have 1 device,
> but you have 4 nodes which looks like separate 4 devices. The
> exception would be if what's on each chip select is independent from
> each other.
>
> Describe what your h/w has/is/does so we can provide better guidance.

This is the hardware design for every implementation with the Elba SoC

  Elba <-- spi --> One FPGA or CPLD (4 chip-selects)

where there are four functions in the FPGA accessed by userspace applications except for emmc reset control which is a bit in a CS0 register.  The IP at CS0 is a bunch of miscellaneous mgmt registers.  CS1 is a designware I2C master/slave.  CS2 is a Lattice dual I2C master.  CS3 is internal storage for the CPLD or FPGA depending on the hardware implementation.

'reg = <0 1 2 3>' in the dt fragment below is indicating the chip-select which is what other bindings appear to be doing.  Maybe one answer is delete this and add our compatible to spidev.c in the patchset we provide to customers.  Adding our compatible to spidev.c was nack'ed. Recommendation?

Not including 'reg' results in this compile warning:

  DTC     arch/arm64/boot/dts/amd/elba-asic.dtb
arch/arm64/boot/dts/amd/elba-asic-common.dtsi:73.28-78.4: Warning (spi_bus_reg): /soc/spi@...0/system-controller@0: missing or empty reg property
arch/arm64/boot/dts/amd/elba-asic-common.dtsi:80.22-84.4: Warning (spi_bus_reg): /soc/spi@...0/system-controller@1: missing or empty reg property
arch/arm64/boot/dts/amd/elba-asic-common.dtsi:86.22-92.4: Warning (spi_bus_reg): /soc/spi@...0/system-controller@2: missing or empty reg property
arch/arm64/boot/dts/amd/elba-asic-common.dtsi:94.22-98.4: Warning (spi_bus_reg): /soc/spi@...0/system-controller@3: missing or empty reg property
  CALL    scripts/atomic/check-atomics.sh

&emmc {
        bus-width = <8>;
        cap-mmc-hw-reset;
        reset-names = "hw";
        resets = <&rstc 0>;
        status = "okay";
};

&spi0 {
        #address-cells = <1>;
        #size-cells = <0>;
        num-cs = <4>;
        cs-gpios = <0>, <0>, <&porta 1 GPIO_ACTIVE_LOW>,
                   <&porta 7 GPIO_ACTIVE_LOW>;
        status = "okay";

        rstc: system-controller@0 {
                compatible = "amd,pensando-elbasr";
                reg = <0>;
                spi-max-frequency = <12000000>;
                #reset-cells = <1>;
        };

        system-controller@1 {
                compatible = "amd,pensando-elbasr";
                reg = <1>;
                spi-max-frequency = <12000000>;
        };

        system-controller@2 {
                compatible = "amd,pensando-elbasr";
                reg = <2>;
                spi-max-frequency = <12000000>;
                interrupt-parent = <&porta>;
                interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
        };

        system-controller@3 {
                compatible = "amd,pensando-elbasr";
                reg = <3>;
                spi-max-frequency = <12000000>;
        };
};

Regards,
Brad

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