linux-kernel - Re: [v5 2/2] dt-bindings: mtd: Add Cadence NAND controller driver

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Date:   Wed, 11 Sep 2019 16:04:24 +0100
From:   Piotr Sroka <piotrs@...ence.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        <devicetree@...r.kernel.org>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Richard Weinberger <richard@....at>,
        Marek Vasut <marek.vasut@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        <linux-mtd@...ts.infradead.org>,
        BrianNorris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Kazuhiro Kasai <kasai.kazuhiro@...ionext.com>
Subject: Re: [v5 2/2] dt-bindings: mtd: Add Cadence NAND controller driver

Hi Miquel

The 08/30/2019 11:46, Miquel Raynal wrote:
>EXTERNAL MAIL
>
>
>Hi Piotr,
>
>Piotr Sroka <piotrs@...ence.com> wrote on Thu, 25 Jul 2019 15:59:55
>+0100:
>
>> Document the bindings used by Cadence NAND controller driver
>>
>> Signed-off-by: Piotr Sroka <piotrs@...ence.com>
>> ---
>> Changes for v5:
>> - replace "_" by "-" in all properties
>> - change compatible name from cdns,hpnfc to cdns,hp-nfc
>> Changes for v4:
>> - add commit message
>> Changes for v3:
>> - add unit suffix for board_delay
>> - move child description to proper place
>> - remove prefix cadence_ for reg and sdma fields
>> Changes for v2:
>> - remove chip dependends parameters from dts bindings
>> - add names for register ranges in dts bindings
>> - add generic bindings to describe NAND chip representation
>> ---
>>  .../bindings/mtd/cadence-nand-controller.txt       | 50 ++++++++++++++++++++++
>>  1 file changed, 50 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt b/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt
>> new file mode 100644
>> index 000000000000..423547a3f993
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt
>> @@ -0,0 +1,50 @@
>> +* Cadence NAND controller
>> +
>> +Required properties:
>> +  - compatible : "cdns,hp-nfc"
>> +  - reg : Contains two entries, each of which is a tuple consisting of a
>> +	  physical address and length. The first entry is the address and
>> +	  length of the controller register set. The second entry is the
>> +	  address and length of the Slave DMA data port.
>> +  - reg-names: should contain "reg" and "sdma"
>> +  - interrupts : The interrupt number.
>> +  - clocks: phandle of the controller core clock (nf_clk).
>> +
>> +Optional properties:
>> +  - dmas: shall reference DMA channel associated to the NAND controller
>> +  - cdns,board-delay-ps : Estimated Board delay. The value includes the total
>> +    round trip delay for the signals and is used for deciding on values
>> +    associated with data read capture. The example formula for SDR mode is
>> +    the following:
>> +    board delay = RE#PAD delay + PCB trace to device + PCB trace from device
>> +    + DQ PAD delay
>> +
>> +Child nodes represent the available NAND chips.
>> +
>> +Required properties of NAND chips:
>> +  - reg: shall contain the native Chip Select ids from 0 to max supported by
>> +    the cadence nand flash controller
>> +
>> +
>> +See Documentation/devicetree/bindings/mtd/nand.txt for more details on
>> +generic bindings.
>> +
>> +Example:
>> +
>> +nand_controller: nand-controller @60000000 {
>> +	  compatible = "cdns,hp-nfc";
>> +	  reg = <0x60000000 0x10000>, <0x80000000 0x10000>;
>> +	  reg-names = "reg", "sdma";
>> +	  clocks = <&nf_clk>;
>> +	  cdns,board-delay-ps = <4830>;
>
>Are you sure you want to export this to the user? Not sure it is easily
>understandable and tunable... I'm not against but I would have troubles
>tuning it myself, unless using the documented value. Maybe you should
>explain more how to derive it?
I need to export this parameter somehow. The default value may not be
valid for other platforms. 
This value depends on platform, and may be different on different SoCs. 
So I think the DTS is the best place to put such configuration
parameter.

>
>The rest looks fine, let's see if Rob agrees. Maybe he will request a
>yaml schema; in this case you can check sunxi NAND bindings which
>already have been converted.
>
>> +	  interrupts = <2 0>;
>> +	  nand@0 {
>> +	      reg = <0>;
>> +	      label = "nand-1";
>> +	  };
>> +	  nand@1 {
>> +	      reg = <1>;
>> +	      label = "nand-2";
>> +	  };
>> +
>> +};
>
>Thanks,
>Miquèl


Thanks
Piotr