On Tue, Apr 17, 2018 at 5:06 PM, Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx> wrote: > On 4/17/2018 11:16 AM, Jae Hyun Yoo wrote: >> >> On 4/17/2018 6:16 AM, Rob Herring wrote: >>> >>> On Mon, Apr 16, 2018 at 6:12 PM, Jae Hyun Yoo >>> <jae.hyun.yoo@xxxxxxxxxxxxxxx> wrote: >>>> >>>> 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. >>> >>> >>> [...] >>> >>>>>> +- 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". >>> >>> >>> No, now you've gone from a standard property name to something custom. >>> Why do you need to set the frequency in DT if it is not related to the >>> interface frequency? >>> >>> Rob >>> >> >> Actually, the interface frequency is affected by the operation frequency >> but there is no description of its relationship in datasheet. I'll check >> again about the detail to ASPEED chip vendor and will use >> 'bus-frequency' if available. >> > > I investigated it more deeply. Basically, by the spec, PECI bus speed > cannot be set as a fixed speed. A PECI bus can have a wide speed range > from 2Kbps to 2Mbps which is dynamically set by a handshaking sequence > between an originator and clients called 'timing negotiation' in spec. > This timing negotiation behavior happens on every single transaction so the > bus speed also can vary on every transactions. So I'm thinking a custom > property name for it, 'peci-clk-frequency' if it is acceptable. Okay, seems bus-frequency is not appropriate here. So use 'clock-frequency' (note the '-' not '_' as that is the standard property). Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
