Re: [PATCH RFC 9/9] dt-bindings: nand: Convert fsl,elbc bindings to YAML

["J. Neuschäfer" <j.ne@posteo.net>]

On Sun, Jan 26, 2025 at 10:23:21PM -0600, Rob Herring wrote:
> On Sun, Jan 26, 2025 at 07:59:04PM +0100, J. Neuschäfer wrote:
> > Convert the Freescale localbus controller bindings from text form to
> > YAML. The list of compatible strings reflects current usage.
> > 
> > Changes compared to the txt version:
> >  - removed the board-control (fsl,mpc8272ads-bcsr) node because it only
> >    appears in this example and nowhere else
> >  - added a new example with NAND flash
> > 
> > Remaining issues:
> >  - The localbus is not really a simple-bus: Unit addresses are not simply
> >    addresses on a memory bus. Instead, they have a format: The first cell
> >    is a chip select number, the remaining one or two cells are bus
> >    addresses.
> 
> That's every external parallel bus. See bindings/memory-controllers/*
> 
> Probably fine to leave 'simple-bus' if that's your question. It's more 
> that there is configuration for the chipselect timings that make's this 
> not a simple-bus. But the address translation should work just fine.

My concern mainly stems from the resulting warnings if I allow/use simple-bus:

Documentation/devicetree/bindings/memory-controllers/fsl,elbc.example.dts:77.23-84.15:
  Warning (simple_bus_reg): /example-1/localbus@e0005000/flash@0,0: simple-bus unit address format error, expected "0"
Documentation/devicetree/bindings/memory-controllers/fsl,elbc.example.dts:86.22-92.15:
  Warning (simple_bus_reg): /example-1/localbus@e0005000/nand@1,0: simple-bus unit address format error, expected "100000000"

Existing devicetrees specify the eLBC with compatible = ..., "simple-bus",
which lead me to include the simple-bus compatible both in the binding
itself and in the examples, which in turn leads to (correct) warnings
from DTC about node names such as nand@1,0 (it expects 100000000).
nand@1,0 was however completely correct for the eLBC bus, because it's
not one big linear address, but rather a chip select (1) and an address (0).

My current idea to resolve this contradiction is to remove simple-bus
from the binding and change affected devicetrees later.

> 
> > 
> > Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
> > ---
> >  .../devicetree/bindings/mtd/fsl,elbc-fcm-nand.yaml |  61 +++++++++
> >  .../bindings/powerpc/fsl/fsl,elbc-gpcm-uio.yaml    |  55 ++++++++
> >  .../devicetree/bindings/powerpc/fsl/fsl,elbc.yaml  | 150 +++++++++++++++++++++
> >  .../devicetree/bindings/powerpc/fsl/lbc.txt        |  43 ------
> >  4 files changed, 266 insertions(+), 43 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/mtd/fsl,elbc-fcm-nand.yaml b/Documentation/devicetree/bindings/mtd/fsl,elbc-fcm-nand.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..127f164443972bbaf50fd9daa80c504577ddd7bd
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/fsl,elbc-fcm-nand.yaml
> > @@ -0,0 +1,61 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mtd/fsl,elbc-fcm-nand.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: NAND flash attached to Freescale eLBC
> > +
> > +maintainers:
> > +  - J. Neuschäfer <j.ne@posteo.net>
> > +
> > +allOf:
> > +  - $ref: nand-chip.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> 
> Don't need oneOf.

How would I express "either one of various chip-specific strings
followed by fsl,elbc-fcm-nand, or fsl,elbc-fcm-nand alone"?

> 
> > +      - items:
> > +          - enum:
> > +              - fsl,mpc8313-fcm-nand
> > +              - fsl,mpc8315-fcm-nand
> > +              - fsl,mpc8377-fcm-nand
> > +              - fsl,mpc8378-fcm-nand
> > +              - fsl,mpc8379-fcm-nand
> > +              - fsl,mpc8536-fcm-nand
> > +              - fsl,mpc8569-fcm-nand
> > +              - fsl,mpc8572-fcm-nand
> > +              - fsl,p1020-fcm-nand
> > +              - fsl,p1021-fcm-nand
> > +              - fsl,p1025-fcm-nand
> > +              - fsl,p2020-fcm-nand
> > +          - const: fsl,elbc-fcm-nand
> > +      - const: fsl,elbc-fcm-nand
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  "#address-cells": true
> > +
> > +  "#size-cells": true
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +additionalProperties: false
> 
> If you use anything from nand-chip.yaml, then you need 
> unevaluatedProperties here.

Noted, will fix.

> 
> > +
> > +examples:
> > +  - |
> > +    localbus {
> > +        #address-cells = <2>;
> > +        #size-cells = <1>;
> > +
> > +        nand@1,0 {
> > +            #address-cells = <1>;
> > +            #size-cells = <1>;
> > +            compatible = "fsl,mpc8315-fcm-nand",
> > +                         "fsl,elbc-fcm-nand";
> > +            reg = <0x1 0x0 0x2000>;
> > +        };
> > +    };
> > diff --git a/Documentation/devicetree/bindings/powerpc/fsl/fsl,elbc-gpcm-uio.yaml b/Documentation/devicetree/bindings/powerpc/fsl/fsl,elbc-gpcm-uio.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..60f849b79c11a4060f2fa4ab163f9fa9317df130
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/powerpc/fsl/fsl,elbc-gpcm-uio.yaml
> > @@ -0,0 +1,55 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/powerpc/fsl/fsl,elbc-gpcm-uio.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Userspace I/O interface for Freescale eLBC devices
> > +
> > +maintainers:
> > +  - J. Neuschäfer <j.ne@posteo.net>
> > +
> > +properties:
> > +  compatible:
> > +    const: fsl,elbc-gpcm-uio
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  elbc-gpcm-br:
> > +    description: Base Register (BR) value to set
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  elbc-gpcm-or:
> > +    description: Option Register (OR) value to set
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  device_type: true
> 
> This should be dropped.

Will do


> > diff --git a/Documentation/devicetree/bindings/powerpc/fsl/fsl,elbc.yaml b/Documentation/devicetree/bindings/powerpc/fsl/fsl,elbc.yaml
[...]
> > +  "#address-cells":
> > +    enum: [2, 3]
> > +    description: |
> 
> Don't need '|' unless there's some formatting.

Will remove.

> 
> > +      The first cell is the chipselect number, and the remaining cells are the
> > +      offset into the chipselect.
> > +
> > +  "#size-cells":
> > +    enum: [1, 2]
> > +    description: |
> > +      Either one or two, depending on how large each chipselect can be.
> > +
> > +  ranges:
> > +    description: |
> > +      Each range corresponds to a single chipselect, and covers the entire
> > +      access window as configured.
> > +
> > +patternProperties:
> > +  "^.*@.*$":
> 
> You should define the unit-address format here: @<chipselect>,<offset>

Will do.



Thanks,
J. Neuschäfer