Re: [DO NOT MERGE v6 22/37] dt-bindings: display: smi,sm501: SMI SM501 binding json-schema

[Geert Uytterhoeven]

Hi Sato-san,

On Tue, Jan 9, 2024 at 9:24 AM Yoshinori Sato
<ysato@xxxxxxxxxxxxxxxxxxxx> wrote:
> Signed-off-by: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>

Thanks for your patch!

> ---
>  .../bindings/display/smi,sm501.yaml           | 417 ++++++++++++++++++
>  1 file changed, 417 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/smi,sm501.yaml

Surely Documentation/devicetree/bindings/display/sm501fb.txt should
be removed, too?

> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/smi,sm501.yaml

> +  crt:
> +    type: object
> +    description: CRT output control
> +    properties:
> +      edid:
> +        $ref: /schemas/types.yaml#/definitions/uint8-array
> +        description: |
> +          verbatim EDID data block describing attached display.
> +          Data from the detailed timing descriptor will be used to
> +          program the display controller.
> +
> +      smi,flags:
> +        $ref: /schemas/types.yaml#/definitions/string-array
> +        description: Display control flags.
> +        items:
> +          anyOf:
> +            - const: use-init-done
> +            - const: disable-at-exit
> +            - const: use-hwcursor
> +            - const: use-hwaccel

The "use-*" flags look like software policy, not hardware description,
and thus do not belong in DT?

> +            - const: panel-no-fpen
> +            - const: panel-no-vbiasen
> +            - const: panel-inv-fpen
> +            - const: panel-inv-vbiasen
> +        maxItems: 8
> +
> +      bpp:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: Color depth
> +
> +  panel:
> +    type: object
> +    description: Panel output control
> +    properties:
> +      edid:
> +        $ref: /schemas/types.yaml#/definitions/uint8-array
> +        description: |
> +          verbatim EDID data block describing attached display.
> +          Data from the detailed timing descriptor will be used to
> +          program the display controller.
> +
> +      smi,flags:
> +        $ref: /schemas/types.yaml#/definitions/string-array
> +        description: Display control flags.
> +        items:
> +          anyOf:
> +            - const: use-init-done
> +            - const: disable-at-exit
> +            - const: use-hwcursor
> +            - const: use-hwaccel

The "use-*" flags look like software policy, not hardware description,
and thus do not belong in DT?

> +            - const: panel-no-fpen
> +            - const: panel-no-vbiasen
> +            - const: panel-inv-fpen
> +            - const: panel-inv-vbiasen
> +        maxItems: 8
> +
> +      bpp:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: Color depth
> +
> +  smi,devices:
> +    $ref: /schemas/types.yaml#/definitions/string-array
> +    description: Select SM501 device functions.
> +    items:
> +      anyOf:
> +        - const: usb-host
> +        - const: usb-slave
> +        - const: ssp0
> +        - const: ssp1
> +        - const: uart0
> +        - const: uart1
> +        - const: fbaccel
> +        - const: ac97
> +        - const: i2s
> +        - const: gpio
> +    minItems: 1
> +    maxItems: 10

I think it would be better to have individual subnodes for the sub devices,
with status = "ok"/"disabled".

If you go that route, you do need some fallback code to handle the lack
of subnodes in the existing user in arch/powerpc/boot/dts/charon.dts.

BTW, why can sm501_pci_initdata get away with setting ".devices
= SM501_USE_ALL"?  Or, would it hurt to enable all subdevices
unconditionally?

> +
> +  smi,mclk:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: mclk frequency.
> +
> +  smi,m1xclk:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: m1xclk frequency.

These two should be clock specifiers (i.e. phandles pointing to clock
nodes + optional clock indices).

> +
> +  misc-timing:
> +    type: object
> +    description: Miscellaneous Timing register values.
> +    properties:
> +      ex:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: Extend bus holding time.
> +        enum: [0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240]
> +
> +      xc:
> +        $ref: /schemas/types.yaml#/definitions/string
> +        description: Xscale clock input select.
> +        items:
> +          enum:
> +            - internal-pll
> +            - hclk
> +            - gpio33

Software policy instead of hardware description again?

I am not familiar with how the SM501 works, so I cannot comment on
the other properties, but several of them look like they need rework.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds