linux-kernel - Re: [PATCH v2 1/2] dt-bindings: Document the STM32 QSPI bindings

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Date:   Tue, 4 Apr 2017 09:28:33 +0200
From:   Ludovic BARRE <ludovic.barre@...com>
To:     Rob Herring <robh@...nel.org>
CC:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Marek Vasut <marek.vasut@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: Document the STM32 QSPI bindings

Hi Rob

thanks for review
my comments below

br
Ludo

On 04/03/2017 06:57 PM, Rob Herring wrote:
> On Fri, Mar 31, 2017 at 07:02:03PM +0200, Ludovic Barre wrote:
>> From: Ludovic Barre <ludovic.barre@...com>
>>
>> This patch adds documentation of device tree bindings for the STM32
>> QSPI controller.
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
>> ---
>>   .../devicetree/bindings/mtd/stm32-quadspi.txt      | 45 ++++++++++++++++++++++
>>   1 file changed, 45 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt b/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
>> new file mode 100644
>> index 0000000..95a8ebd
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
>> @@ -0,0 +1,45 @@
>> +* STMicroelectronics Quad Serial Peripheral Interface(QuadSPI)
>> +
>> +Required properties:
>> +- compatible: should be "st,stm32f469-qspi"
>> +- reg: contains the register location and length.
>> +  (optional) the memory mapping address and length
> Why optional? Either the h/w has it or doesn't. If some chips don't,
> they should have a different compatible string.
in fact, the stm32 qspi controller can operate in any of the following 
modes:
-indirect mode: all the operations are performed using the qspi registers
with read/write.
-read memory-mapped mode: the external Flash memory is mapped to the
  microcontroller address space and is seen by the system as if it was
  an internal memory (use memcpy_fromio). this mode improve read throughput

if qspi_mm is defined the qspi controller use read memory-mapped mode
else the controller transfers in indirect mode.
>> +- reg-names: list of the names corresponding to the previous register
>> +  Should contain "qspi" to register location
>> +  (optional) "qspi_mm" if read in memory map mode (improve read throughput)
>> +- interrupts: should contain the interrupt for the device
>> +- clocks: the phandle of the clock needed by the QSPI controller
>> +- A pinctrl must be defined to set pins in mode of operation for QSPI transfer
>> +
>> +Optional properties:
>> +- resets: must contain the phandle to the reset controller.
>> +
>> +A spi flash must be a child of the nor_flash node and could have some
>> +properties. Also see jedec,spi-nor.txt.
>> +
>> +Required properties:
>> +- reg: chip-Select number (QSPI controller may connect 2 nor flashes)
>> +- spi-max-frequency: max frequency of spi bus
>> +
>> +Optional property:
>> +- spi-rx-bus-width: the bus width (number of data wires)
> Just "see ../spi/spi-bus.txt" for the description
ok
>
>> +
>> +Example:
>> +
>> +qspi: qspi@...01000 {
> spi@...
ok
>> +	compatible = "st,stm32f469-qspi";
>> +	reg = <0xa0001000 0x1000>, <0x90000000 0x10000000>;
>> +	reg-names = "qspi", "qspi_mm";
>> +	interrupts = <91>;
>> +	resets = <&rcc STM32F4_AHB3_RESET(QSPI)>;
>> +	clocks = <&rcc 0 STM32F4_AHB3_CLOCK(QSPI)>;
>> +	pinctrl-names = "default";
>> +	pinctrl-0 = <&pinctrl_qspi0>;
>> +
>> +	flash@0 {
>> +		reg = <0>;
>> +		spi-rx-bus-width = <4>;
>> +		spi-max-frequency = <108000000>;
>> +		...
>> +	};
>> +};
>> -- 
>> 2.7.4
>>