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

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Message-ID: <8d20ba5443fe0f74798a2a7d81140d3c6462cada.camel@mediatek.com>
Date: Sat, 8 Feb 2025 04:33:28 +0000
From: Crystal Guo (郭晶) <Crystal.Guo@...iatek.com>
To: "robh@...nel.org" <robh@...nel.org>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>, "krzk@...nel.org"
	<krzk@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>
CC: "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH 2/2] dt-bindings: memory-controllers: Add mediatek
 common-dramc dt-bindings

On Thu, 2024-12-12 at 11:27 +0100, AngeloGioacchino Del Regno wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> 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@...iatek.com>
> > ---
> >   .../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
> > +---
> > +$id: 
> > https://urldefense.com/v3/__http://devicetree.org/schemas/memory-controllers/mediatek,common-dramc.yaml*__;Iw!!CTRNKA9wMg0ARbw!hkObFeP7J-uvNSyDsepqqdH_jZQcf9NQ1knBRGY1ODpH6FoZyBzL1x5rEIWPppp1wNmLdo41PQTZM4ulMP1Qg7wr9PwFEdeN$
> > +$schema: 
> > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!hkObFeP7J-uvNSyDsepqqdH_jZQcf9NQ1knBRGY1ODpH6FoZyBzL1x5rEIWPppp1wNmLdo41PQTZM4ulMP1Qg7wr9FN7m95w$
> > +
> > +title: MediaTek Common DRAMC (DRAM Controller)
> 
> MediaTek DRAM Controller (DRAMC)
> 
> > +
> > +maintainers:
> > +  - Crystal Guo <crystal.guo@...iatek.com>
> > +
> > +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
> 

Thanks for your review.
Based on the above suggestions, I have simplified the parameters that
need to be passed into the DTS.
- Only the base address need to pass through the DTS;
- "fmeter version" is placed in the platform data;
- The values of "pll-id", "shu-lv"..., can be directly read in the
driver through predefined register offsets and masks.

v2: https://patchwork.kernel.org/patch/13964209

Thanks
Crystal