linux-kernel - Re: [RFC PATCH 2/2] dt-bindings: spi: QuadSPI driver for Atmel SAMA5D2 documentation

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Date:   Thu, 21 Jun 2018 12:56:50 +0200 (CEST)
From:   Piotr Bugalski <bugalski.piotr@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
cc:     Piotr Bugalski <bugalski.piotr@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Cyrille Pitchen <cyrille.pitchen@...rochip.com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Piotr Bugalski <pbu@...ptera.com>
Subject: Re: [RFC PATCH 2/2] dt-bindings: spi: QuadSPI driver for Atmel
 SAMA5D2 documentation


Hi Boris,

On Wed, 20 Jun 2018, Boris Brezillon wrote:

> Hi Piotr,
>
> On Mon, 18 Jun 2018 18:21:24 +0200
> Piotr Bugalski <bugalski.piotr@...il.com> wrote:
>
>> Documentation for DT-binding change.
>>
>> Suggested-by: Boris Brezillon <boris.brezillon@...tlin.com>
>
> I'm pretty sure I didn't make a single suggestion about the DT
> bindings you use here ;-).
>

Ok, I misunderstood a bit your idea, but I think from next release this
field will be in good place. So it was just prepared for the future ;-)

>> Signed-off-by: Piotr Bugalski <pbu@...ptera.com>
>>
>> ---
>>  .../devicetree/bindings/spi/spi_atmel-qspi.txt     | 41 ++++++++++++++++++++++
>>  1 file changed, 41 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/spi/spi_atmel-qspi.txt
>
> I'll comment on this aspect in more details when replying to the cover
> letter, but I think you should re-use the bindings defined in
> Documentation/devicetree/bindings/mtd/atmel-quadspi.txt (IOW, move the
> existing file to the Documentation/devicetree/bindings/spi directory).
>
> It's the same HW block, and just because you develop a new driver to
> replace the old one doesn't mean you should have 2 different bindings in
> parallel.

I'll change it in next version.

>
>>
>> diff --git a/Documentation/devicetree/bindings/spi/spi_atmel-qspi.txt b/Documentation/devicetree/bindings/spi/spi_atmel-qspi.txt
>> new file mode 100644
>> index 000000000000..d52b534c9c2b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/spi/spi_atmel-qspi.txt
>> @@ -0,0 +1,41 @@
>> +* Atmel Quad Serial Peripheral Interface (QSPI)
>> +
>> +Required properties:
>> +- compatible:     Should be "atmel,sama5d2-spi-qspi".
>> +- reg:            Should contain the locations and lengths of the base registers
>> +                  and the mapped memory.
>> +- reg-names:      Should contain the resource reg names:
>> +                  - qspi_base: configuration register address space
>> +                  - qspi_mmap: memory mapped address space
>> +- interrupts:     Should contain the interrupt for the device.
>> +- clocks:         The phandle of the clock needed by the QSPI controller.
>> +- #address-cells: Should be <1>.
>> +- #size-cells:    Should be <0>.
>> +
>> +Example:
>> +
>> +qspi1: spi@...24000 {
>> +	compatible = "atmel,sama5d2-spi-qspi";
>> +	reg = <0xf0024000 0x100>, <0xd8000000 0x08000000>;
>> +	reg-names = "qspi_base", "qspi_mmap";
>> +	interrupts = <53 IRQ_TYPE_LEVEL_HIGH 7>;
>> +	clocks = <&qspi1_clk>;
>> +	#address-cells = <1>;
>> +	#size-cells = <0>;
>> +	pinctrl-names = "default";
>> +	pinctrl-0 = <&pinctrl_qspi1_default>;
>> +	status = "okay";
>> +
>> +	flash@0 {
>> +		#address-cells = <1>;
>> +		#size-cells = <1>;
>> +		compatible = "winbond,w25m02gv", "spi-nand";
>
> "winbond,w25m02gv" is undocumented and unnecessary since SPI NANDs are
> automatically detected. Also, maybe you should declare a SPI NOR in the
> example since SPI NAND support has not yet been merged.
>

I was mainly focusing on NAND-flash with QSPI inteface so I took
example from tested configuration. Next time I'll use NOR-flash.

>> +		reg = <0>;
>> +		spi-max-frequency = <83000000>;
>> +		spi-rx-bus-width = <4>;
>> +		spi-tx-bus-width = <4>;
>> +
>> +		...
>> +	};
>> +};
>> +
>
> Regards,
>
> Boris
>

Thanks,
Piotr