Re: [PATCH 2/2] dt-bindings: memory-controllers: Add mediatek common-dramc dt-bindings

[AngeloGioacchino Del Regno]

Il 12/12/24 09:59, Crystal Guo ha scritto:
> Add devicetree binding for mediatek common-dramc driver.
>
> The DRAM controller of MediaTek SoC provides an interface to
> get the current data rate of DRAM.
>
> Signed-off-by: Crystal Guo <crystal.guo@xxxxxxxxxxxx>
> ---
>   .../mediatek,common-dramc.yaml                | 129 ++++++++++++++++++
>   1 file changed, 129 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/memory-controllers/mediatek,common-dramc.yaml
>
> diff --git a/Documentation/devicetree/bindings/memory-controllers/mediatek,common-dramc.yaml b/Documentation/devicetree/bindings/memory-controllers/mediatek,common-dramc.yaml
> new file mode 100644
> index 000000000000..c9e608c7f183
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/memory-controllers/mediatek,common-dramc.yaml
> @@ -0,0 +1,129 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +# Copyright (c) 2024 MediaTek Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/memory-controllers/mediatek,common-dramc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: MediaTek Common DRAMC (DRAM Controller)

MediaTek DRAM Controller (DRAMC)

> +
> +maintainers:
> +  - Crystal Guo <crystal.guo@xxxxxxxxxxxx>
> +
> +description: |
> +  The DRAM controller of MediaTek SoC provides an interface to
> +  get the current data rate of DRAM.

No, the DRAM Controller does much more than just that.

> +
> +properties:
> +  compatible:
> +    const: mediatek,common-dramc

Absolutely no! Compatibles are per-soc.

mediatek,mt8186-dramc
mediatek,mt8188-dramc
mediatek,mt8195-dramc

etc

> +
> +  reg:
> +    minItems: 9
> +    items:
> +      - description: DRAMC_AO_CHA_BASE
> +      - description: DRAMC_AO_CHB_BASE
> +      - description: DRAMC_AO_CHC_BASE
> +      - description: DRAMC_AO_CHD_BASE

All those channels are sequential in AO->NAO, in the sense that
every channel is:

CH0     AO: 0x10230000   len: 0x4000
CH0    NAO: 0x10234000   len: 0x2000
CH0 PHY_AO: 0x10236000   len: 0x2000
CH0 PHY_AO: 0x10238000   len: 0x2000

So the reg can be simplified as

minItems: 4
items:
  - description: DRAM Controller Channel 0
  - description: DRAM Controller Channel 1
  - description: DRAM Controller Channel 2
  - description: DRAM Controller Channel 3


> +      - description: DRAMC_NAO_CHA_BASE
> +      - description: DRAMC_NAO_CHB_BASE
> +      - description: DRAMC_NAO_CHC_BASE
> +      - description: DRAMC_NAO_CHD_BASE
> +      - description: DDRPHY_AO_CHA_BASE
> +      - description: DDRPHY_AO_CHB_BASE
> +      - description: DDRPHY_AO_CHC_BASE
> +      - description: DDRPHY_AO_CHD_BASE
> +      - description: DDRPHY_NAO_CHA_BASE
> +      - description: DDRPHY_NAO_CHB_BASE
> +      - description: DDRPHY_NAO_CHC_BASE
> +      - description: DDRPHY_NAO_CHD_BASE
> +      - description: SLEEP_BASE

You're not using the SLEEP_BASE iospace, and that's not even really specific
to the DRAM Controller. Drop it.

> +
> +  support-ch-cnt:
> +    maxItems: 1

Don't tell me that the DRAM Controller in MediaTek SoCs cannot see how many
channels are actually occupied by a DRAM bank, because I will be really skeptical.

You can autodetect that in the driver, you don't need a DT property for that.

> +
> +  fmeter-version:
> +    maxItems: 1
> +    description:
> +      Fmeter version for calculating dram data rate

The Fmeter version is SoC-specific, you need platform data, not DT property.

> +
> +  crystal-freq:
> +    maxItems: 1
> +    description:
> +      Reference clock rate in MHz

Is this crystal an external component, or is it integrated into the SoC?

> +
> +  shu-of:
> +    maxItems: 1

There's no description, what is shu-of?

> +
> +  pll-id: true
> +  shu-lv: true
> +  sdmpcw: true
> +  posdiv: true
> +  fbksel: true
> +  dqsopen: true
> +  async-ca: true
> +  dq-ser-mode: true

Same for these ones, please describe them - but then remember: if those parameters
are board-specific, they can stay here, otherwise those go in platform data.

Besides, I doubt that those are board specific.

Regards,
Angelo