Re: [PATCH v3 04/10] Documentations: dt-bindings: Add a document of PECI adapter driver for Aspeed AST24xx/25xx SoCs

[Jae Hyun Yoo]

On 4/16/2018 11:10 AM, Rob Herring wrote:
> On Tue, Apr 10, 2018 at 11:32:06AM -0700, Jae Hyun Yoo wrote:
> > This commit adds a dt-bindings document of PECI adapter driver for Aspeed
> > AST24xx/25xx SoCs.
> >
> > Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx>
> > Reviewed-by: Haiyue Wang <haiyue.wang@xxxxxxxxxxxxxxx>
> > Reviewed-by: James Feist <james.feist@xxxxxxxxxxxxxxx>
> > Reviewed-by: Vernon Mauery <vernon.mauery@xxxxxxxxxxxxxxx>
> > Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
> > Cc: Andrew Jeffery <andrew@xxxxxxxx>
> > Cc: Andrew Lunn <andrew@xxxxxxx>
> > Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
> > Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Cc: Jason M Biils <jason.m.bills@xxxxxxxxxxxxxxx>
> > Cc: Jean Delvare <jdelvare@xxxxxxxx>
> > Cc: Joel Stanley <joel@xxxxxxxxx>
> > Cc: Julia Cartwright <juliac@xxxxxxxxxxxx>
> > Cc: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
> > Cc: Milton Miller II <miltonm@xxxxxxxxxx>
> > Cc: Pavel Machek <pavel@xxxxxx>
> > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Cc: Stef van Os <stef.van.os@xxxxxxxxxxxxxxxxxxxxxxxxx>
> > Cc: Sumeet R Pawnikar <sumeet.r.pawnikar@xxxxxxxxx>
> > ---
> >   .../devicetree/bindings/peci/peci-aspeed.txt       | 60 ++++++++++++++++++++++
> >   1 file changed, 60 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/peci/peci-aspeed.txt
> >
> > diff --git a/Documentation/devicetree/bindings/peci/peci-aspeed.txt b/Documentation/devicetree/bindings/peci/peci-aspeed.txt
> > new file mode 100644
> > index 000000000000..4598bb8c20fa
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/peci/peci-aspeed.txt
> > @@ -0,0 +1,60 @@
> > +Device tree configuration for PECI buses on the AST24XX and AST25XX SoCs.
> > +
> > +Required properties:
> > +- compatible        : Should be "aspeed,ast2400-peci" or "aspeed,ast2500-peci"
> > +		      - aspeed,ast2400-peci: Aspeed AST2400 family PECI
> > +					     controller
> > +		      - aspeed,ast2500-peci: Aspeed AST2500 family PECI
> > +					     controller
> > +- reg               : Should contain PECI controller registers location and
> > +		      length.
> > +- #address-cells    : Should be <1>.
> > +- #size-cells       : Should be <0>.
> > +- interrupts        : Should contain PECI controller interrupt.
> > +- clocks            : Should contain clock source for PECI controller.
> > +		      Should reference clkin.
> > +- clock_frequency   : Should contain the operation frequency of PECI controller
> > +		      in units of Hz.
> > +		      187500 ~ 24000000
>
> This is the frequency of the bus or used to derive it? It would be
> better to specify the bus frequency instead and have the driver
> calculate its internal freq. And then use "bus-frequency" instead.

I agree with you. Actually, it is being used for operation frequency 
setting of PECI controller module in SoC so it's different from the 
meaning of "bus-frequency". I'll change it to "operation-frequency".

> > +
> > +Optional properties:
> > +- msg-timing-nego   : Message timing negotiation period. This value will
> > +		      determine the period of message timing negotiation to be
> > +		      issued by PECI controller. The unit of the programmed
> > +		      value is four times of PECI clock period.
> > +		      0 ~ 255 (default: 1)
> > +- addr-timing-nego  : Address timing negotiation period. This value will
> > +		      determine the period of address timing negotiation to be
> > +		      issued by PECI controller. The unit of the programmed
> > +		      value is four times of PECI clock period.
> > +		      0 ~ 255 (default: 1)
> > +- rd-sampling-point : Read sampling point selection. The whole period of a bit
> > +		      time will be divided into 16 time frames. This value will
> > +		      determine the time frame in which the controller will
> > +		      sample PECI signal for data read back. Usually in the
> > +		      middle of a bit time is the best.
> > +		      0 ~ 15 (default: 8)
> > +- cmd_timeout_ms    : Command timeout in units of ms.
> > +		      1 ~ 60000 (default: 1000)
>
> s/_/-/

Will fix it.

> All these either need vendor prefixes or should be standard properties
> for PECI adapters. I think probably the latter case. If so, the first
> 2 should probably be in units of clocks (not 4 clocks). And they should
> then be documented in the common PECI binding doc.

So far I've checked that these are ASPEED PECI controller specific 
properties so it should be listed in here.

> > +
> > +Example:
> > +	peci: peci@1e78b000 {
> > +		compatible = "simple-bus";
> > +		#address-cells = <1>;
> > +		#size-cells = <1>;
> > +		ranges = <0x0 0x1e78b000 0x60>;
>
> No need to show this part in examples.

Got it. Will drop the part.

> > +
> > +		peci0: peci-bus@0 {
> > +			compatible = "aspeed,ast2500-peci";
> > +			reg = <0x0 0x60>;
> > +			#address-cells = <1>;
> > +			#size-cells = <0>;
> > +			interrupts = <15>;
> > +			clocks = <&clk_clkin>;
> > +			clock-frequency = <24000000>;
> > +			msg-timing-nego = <1>;
> > +			addr-timing-nego = <1>;
> > +			rd-sampling-point = <8>;
> > +			cmd-timeout-ms = <1000>;
> > +		};
> > +	};
> > --
> > 2.16.2
> >
> > --
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