linux-kernel - Re: [PATCH v12 1/4] dt-bindings: spi: Add schema for Cadence QSPI Controller driver

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Message-ID: <13a92ddd-b7dd-0465-d747-cda9bca21dbf@linux.intel.com>
Date:   Fri, 20 Mar 2020 14:19:37 +0800
From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
To:     Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        broonie@...nel.org, robh+dt@...nel.org
Cc:     devicetree@...r.kernel.org, boris.brezillon@...e-electrons.com,
        simon.k.r.goldschmidt@...il.com, dinguyen@...nel.org,
        tien.fong.chee@...el.com, marex@...x.de,
        linux-mtd@...ts.infradead.org, dwmw2@...radead.org, richard@....at,
        computersforpeace@...il.com, cyrille.pitchen@...el.com,
        david.oberhollenzer@...ma-star.at, miquel.raynal@...tlin.com,
        tudor.ambarus@...il.com, cheol.yong.kim@...el.com,
        qi-ming.wu@...el.com
Subject: Re: [PATCH v12 1/4] dt-bindings: spi: Add schema for Cadence QSPI
 Controller driver

Hi,

On 20/3/2020 2:05 pm, Vignesh Raghavendra wrote:
>
> On 10/03/20 7:22 am, Ramuthevar,Vadivel MuruganX wrote:
>> From: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@...ux.intel.com>
>>
>> Add dt-bindings documentation for Cadence-QSPI controller to support
>> spi based flash memories.
>>
>> Signed-off-by: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@...ux.intel.com>
>> ---
>>   .../devicetree/bindings/mtd/cadence-quadspi.txt    |  67 -----------
>>   .../devicetree/bindings/spi/cdns,qspi-nor.yaml     | 127 +++++++++++++++++++++
>>   2 files changed, 127 insertions(+), 67 deletions(-)
>>   delete mode 100644 Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
>>   create mode 100644 Documentation/devicetree/bindings/spi/cdns,qspi-nor.yaml
>>
> [...]
>
>> +
>> +# subnode's properties
>> +patternProperties:
>> +  "^.*@[0-9a-fA-F]+$":
>> +    type: object
>> +    description:
>> +      flash device uses the subnodes below defined properties.
>> +
>> +  cdns,read-delay:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description:
>> +      Delay in 4 microseconds, read capture logic, in clock cycles.
>
> Not its not... See the old binding description please:
>
> -- cdns,read-delay : Delay for read capture logic, in clock cycles
>
> There is no mention of 4us. Range is 0x0 - 0xF
Sure, will update as you have suggested.
>> +
>> +  cdns,tshsl-ns:
>> +    description: |
>> +      Delay in 50 nanoseconds, for the length that the master mode chip select
>> +      outputs are de-asserted between transactions.
> Again see the description in old binding file:
>
>   cdns,tshsl-ns : Delay in nanoseconds for the length that the master
>                    mode chip select outputs are de-asserted between
> 	  	transactions.
>
> Need not be 50ns or its multiple
Sure, will update as you have suggested.
>> +
>> +  cdns,tsd2d-ns:
>> +    description: |
>> +      Delay in 50 nanoseconds, between one chip select being de-activated
>> +      and the activation of another.
>> +
> same here
>
>> +  cdns,tchsh-ns:
>> +    description: |
>> +      Delay in 4 nanoseconds, between last bit of current transaction and
>> +      deasserting the device chip select (qspi_n_ss_out).
>> +
> Same here... Need not be 4ns...
>
>> +  cdns,tslch-ns:
>> +    description: |
>> +      Delay in 4 nanoseconds, between setting qspi_n_ss_out low and
>> +      first bit transfer.
>
> Same here...
>
> Above four values ( cdns,*-ns) come directly from the flash datasheets.
>
> These values are converted appropriate number of cycles depending upon
> the QSPI ref_clk frequency. So, there is no easy way to express the
> constraint (or range) in DT schema. I would recommend to just stick with
> the description that is there in the old binding file without any
> modifications.

Noted, will update.

Regards
Vadivel
>
> Regards
> Vignesh