Message-ID: <5dfac2d7-3b4b-9ded-0dde-26b289c604d0@broadcom.com>
Date:   Mon, 9 Jan 2023 00:27:19 -0800
From:   William Zhang <william.zhang@...adcom.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Linux SPI List <linux-spi@...r.kernel.org>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>
Cc:     anand.gore@...adcom.com, tomer.yacoby@...adcom.com,
        dan.beygelman@...adcom.com, joel.peshkin@...adcom.com,
        f.fainelli@...il.com, jonas.gorski@...il.com,
        kursad.oney@...adcom.com, dregan@...l.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/16] dt-bindings: spi: Add bcmbca-hsspi controller
 support

Hi Krzysztof,

On 01/08/2023 06:51 AM, Krzysztof Kozlowski wrote:
> On 06/01/2023 21:07, William Zhang wrote:
>> The new Broadcom Broadband BCMBCA SoCs includes a updated HSSPI
>> controller. Add a new compatible string and required fields for the new
>> driver.  Also add myself and Kursad as the maintainers.
>>
>> Signed-off-by: William Zhang <william.zhang@...adcom.com>
>> ---
>>
>>   .../bindings/spi/brcm,bcm63xx-hsspi.yaml      | 84 +++++++++++++++++--
>>   1 file changed, 78 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/spi/brcm,bcm63xx-hsspi.yaml b/Documentation/devicetree/bindings/spi/brcm,bcm63xx-hsspi.yaml
>> index 45f1417b1213..56e69d4a1faf 100644
>> --- a/Documentation/devicetree/bindings/spi/brcm,bcm63xx-hsspi.yaml
>> +++ b/Documentation/devicetree/bindings/spi/brcm,bcm63xx-hsspi.yaml
>> @@ -4,22 +4,51 @@
>>   $id: http://devicetree.org/schemas/spi/brcm,bcm63xx-hsspi.yaml#
>>   $schema: http://devicetree.org/meta-schemas/core.yaml#
>>   
>> -title: Broadcom BCM6328 High Speed SPI controller
>> +title: Broadcom Broadband SoC High Speed SPI controller
>>   
>>   maintainers:
>> +
> 
> Drop blank line.
will fix in  v2.

> 
>> +  - William Zhang <william.zhang@...adcom.com>
>> +  - Kursad Oney <kursad.oney@...adcom.com>
>>     - Jonas Gorski <jonas.gorski@...il.com>
> 
>>   
>> +description: |
>> +  Broadcom Broadband SoC supports High Speed SPI master controller since the
>> +  early MIPS based chips such as BCM6328 and BCM63268.  This controller was
>> +  carried over to recent ARM based chips, such as BCM63138, BCM4908 and BCM6858.
>> +
>> +  It has a limitation that can not keep the chip select line active between
>> +  the SPI transfers within the same SPI message. This can terminate the
>> +  transaction to some SPI devices prematurely. The issue can be worked around by
>> +  either the controller's prepend mode or using the dummy chip select
>> +  workaround. This controller uses the compatible string brcm,bcm6328-hsspi.
>> +
>> +  The newer SoCs such as BCM6756, BCM4912 and BCM6855 include an updated SPI
>> +  controller that add the capability to allow the driver to control chip select
>> +  explicitly. This solves the issue in the old controller. This new controller
>> +  uses the compatible string brcm,bcmbca-hsspi.
>> +
>>   properties:
>>     compatible:
>> -    const: brcm,bcm6328-hsspi
>> +    enum:
>> +      - brcm,bcm6328-hsspi
>> +      - brcm,bcmbca-hsspi
> 
> bca seems quite unspecific. Your description above mentions several
> model numbers and "bca" is not listed as model. Compatibles cannot be
> generic.
"bca" is not model number, rather it is a group (broadband carrier 
access) of chip that share the same spi host controller IP. Agree it is 
not particularly specific but it differentiate from other broadcom spi 
controller ip used by other groups.  We just don't have a specific name 
for this spi host controller but can we treat bcmbca as the ip name? 
Otherwise we will have to have a compatible string with chip model for 
each SoC even they share the same IP. We already have more than ten of 
SoCs and the list will increase.  I don't see this is a good solution too.

> 
>>   
>>     reg:
>> -    maxItems: 1
>> +    items:
>> +      - description: main registers
>> +      - description: miscellaneous control registers
>> +    minItems: 1
>> +
>> +  reg-names:
>> +    items:
>> +      - const: hsspi
>> +      - const: spim-ctrl
> 
> This does not match reg
Do you mean it does not match the description?
> 
>>   
>>     clocks:
>>       items:
>> -      - description: spi master reference clock
>> -      - description: spi master pll clock
>> +      - description: SPI master reference clock
>> +      - description: SPI master pll clock
> 
> Really? You just added it in previous patch, didn't you?
The previous patch was just word to word conversion of the text file.  I 
will update that patch to include this change.

> 
>>   
>>     clock-names:
>>       items:
>> @@ -29,12 +58,43 @@ properties:
>>     interrupts:
>>       maxItems: 1
>>   
>> +  brcm,use-cs-workaround:
>> +    $ref: /schemas/types.yaml#/definitions/flag
>> +    description: |
>> +      Enable dummy chip select workaround for SPI transfers that can not be
>> +      supported by the default controller's prepend mode, i.e. delay or cs
>> +      change needed between SPI transfers.
> 
> You need to describe what is the workaround.
Will do.
> 
>> +
>>   required:
>>     - compatible
>>     - reg
>>     - clocks
>>     - clock-names
>> -  - interrupts
>> +
>> +allOf:
>> +  - $ref: "spi-controller.yaml#"
> 
> No quotes. How this is related to this patch?
Will remove quote and put it in patch 1.
> 
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            enum:
>> +              - brcm,bcm6328-hsspi
>> +    then:
>> +      properties:
>> +        reg:
>> +          minItems: 1
> 
> Drop.
> 
> reg-names now do not match.
Don't quite understand your comment. What do I need to drop and what is 
not matched?

> 
>> +          maxItems: 1
>> +    else:
>> +      properties:
>> +        reg:
>> +          minItems: 2
>> +          maxItems: 2
>> +        reg-names:
>> +          minItems: 2
>> +          maxItems: 2
>> +        brcm,use-cs-workaround: false
>> +      required:
>> +        - reg-names
> Best regards,
> Krzysztof
> 

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