linux-kernel - Re: [PATCH 3/5] dt-bindings: mmc: sdhci-cadence: SD6 support

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Message-ID: <20230118160216.GA19078@Dell2s-9>
Date:   Wed, 18 Jan 2023 08:02:16 -0800
From:   Piyush Malgujar <pmalgujar@...vell.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     <linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <adrian.hunter@...el.com>, <ulf.hansson@...aro.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <yamada.masahiro@...ionext.com>, <devicetree@...r.kernel.org>,
        <jannadurai@...vell.com>, <cchavva@...vell.com>
Subject: Re: [PATCH 3/5] dt-bindings: mmc: sdhci-cadence: SD6 support

Hi Krzysztof,

On Sat, Jan 07, 2023 at 02:25:02PM +0100, Krzysztof Kozlowski wrote:
> On 06/01/2023 17:48, Piyush Malgujar wrote:
> > Hi Krzysztof,
> > 
> > Thank you the review comments.
> > 
> > On Mon, Dec 19, 2022 at 04:40:35PM +0100, Krzysztof Kozlowski wrote:
> >> On 19/12/2022 15:24, Piyush Malgujar wrote:
> >>> From: Jayanthi Annadurai <jannadurai@...vell.com>
> >>>
> >>
> >> Subject: use final prefix matching the file, so "cdns,sdhci:"
> >>
> >>> Add support for SD6 controller support
> >>
> >> Full stop.
> >>
> >>>
> >>> Signed-off-by: Jayanthi Annadurai <jannadurai@...vell.com>
> >>> Signed-off-by: Piyush Malgujar <pmalgujar@...vell.com>
> >>> ---
> >>>  .../devicetree/bindings/mmc/cdns,sdhci.yaml   | 33 +++++++++++++++++--
> >>>  1 file changed, 31 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml b/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml
> >>> index 8b1a0fdcb5e3e2e8b87d8d7678e37f3dad447fc1..2043e78ccd5f708a01e87fd96ec410418fcd539f 100644
> >>> --- a/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml
> >>> +++ b/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml
> >>> @@ -4,7 +4,7 @@
> >>>  $id: http://devicetree.org/schemas/mmc/cdns,sdhci.yaml#
> >>>  $schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>  
> >>> -title: Cadence SD/SDIO/eMMC Host Controller (SD4HC)
> >>> +title: Cadence SD/SDIO/eMMC Host Controller (SD4HC, SD6HC)
> >>>  
> >>>  maintainers:
> >>>    - Masahiro Yamada <yamada.masahiro@...ionext.com>
> >>> @@ -19,6 +19,7 @@ properties:
> >>>            - microchip,mpfs-sd4hc
> >>>            - socionext,uniphier-sd4hc
> >>>        - const: cdns,sd4hc
> >>> +      - const: cdns,sd6hc
> >>
> >> Does not look like you tested the DTS against bindings. Please run `make
> >> dtbs_check` (see Documentation/devicetree/bindings/writing-schema.rst
> >> for instructions).
> >>
> >> ... because it does not really make sense. Why do you require SD6HC as
> >> fallback? I think you meant enum.
> >>
> > 
> > Yes, that's correct. I will change it to enum.
> > 
> >>>  
> >>>    reg:
> >>>      maxItems: 1
> >>> @@ -111,6 +112,34 @@ properties:
> >>>      minimum: 0
> >>>      maximum: 0x7f
> >>>  
> >>> +  cdns,iocell_input_delay:
> >>
> >> No underscores. Use proper units in name suffix:
> >> https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml
> >>
> >>
> >>> +    description: Delay in ps across the input IO cells
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>
> >> Ditto... and so on - all of the fields.
> >>
> >>> +
> >>> +  cdns,iocell_output_delay:
> >>> +    description: Delay in ps across the output IO cells
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>> +
> >>> +  cdns,delay_element:
> >>> +    description: Delay element in ps used for calculating phy timings
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>> +
> >>> +  cdns,read_dqs_cmd_delay:
> >>> +    description: Command delay used in HS200 tuning
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>> +
> >>> +  cdns,tune_val_start:
> >>> +    description: Staring value of data delay used in HS200 tuning
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>> +
> >>> +  cdns,tune_val_step:
> >>> +    description: Incremental value of data delay used in HS200 tuning
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>> +
> >>> +  cdns,max_tune_iter:
> >>> +    description: Maximum number of iterations to complete the HS200 tuning process
> >>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
> >>
> >> Why these three are properties of DT?
> >>
> > 
> > These tuning parameters are added here so to make them custom configurable for different
> > boards.
> 
> I understand why do you wanted to add them, but I am asking why these
> are suitable for DT? DT  describes hardware, so what is here specific to
> hardware which requires DT property?
> 
> 

We have different values based on emmc devices populated on different boards and these
tuning parameters are used to program phy registers accordingly.

> Best regards,
> Krzysztof

Thanks,
Piyush>