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

[Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>]

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@linux.intel.com>
>> Reviewed-by: Haiyue Wang <haiyue.wang@linux.intel.com>
>> Reviewed-by: James Feist <james.feist@linux.intel.com>
>> Reviewed-by: Vernon Mauery <vernon.mauery@linux.intel.com>
>> Cc: Alan Cox <alan@linux.intel.com>
>> Cc: Andrew Jeffery <andrew@aj.id.au>
>> Cc: Andrew Lunn <andrew@lunn.ch>
>> Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> Cc: Fengguang Wu <fengguang.wu@intel.com>
>> Cc: Greg KH <gregkh@linuxfoundation.org>
>> Cc: Guenter Roeck <linux@roeck-us.net>
>> Cc: Jason M Biils <jason.m.bills@linux.intel.com>
>> Cc: Jean Delvare <jdelvare@suse.com>
>> Cc: Joel Stanley <joel@jms.id.au>
>> Cc: Julia Cartwright <juliac@eso.teric.us>
>> Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
>> Cc: Milton Miller II <miltonm@us.ibm.com>
>> Cc: Pavel Machek <pavel@ucw.cz>
>> Cc: Randy Dunlap <rdunlap@infradead.org>
>> Cc: Stef van Os <stef.van.os@prodrive-technologies.com>
>> Cc: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
>> ---
>>   .../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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