From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jae Hyun Yoo Subject: Re: [PATCH v3 04/10] Documentations: dt-bindings: Add a document of PECI adapter driver for Aspeed AST24xx/25xx SoCs Date: Wed, 18 Apr 2018 09:45:56 -0700 Message-ID: <7ff3b23c-7dc8-865f-4069-c53642aaf1ab@linux.intel.com> References: <20180410183212.16787-1-jae.hyun.yoo@linux.intel.com> <20180410183212.16787-5-jae.hyun.yoo@linux.intel.com> <20180416181035.rcjvt4rlrwaj5yxf@rob-hp-laptop> <53ff5b2b-eba8-8311-64a9-abd4bc72226d@linux.intel.com> <584aca6c-c87a-ff7a-2fdc-3c742236be60@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: Alan Cox , Andrew Jeffery , Andrew Lunn , Andy Shevchenko , Arnd Bergmann , Benjamin Herrenschmidt , Fengguang Wu , Greg KH , Guenter Roeck , Haiyue Wang , James Feist , Jason M Biils , Jean Delvare , Joel Stanley , Julia Cartwright , Miguel Ojeda , Milton Miller II , Pavel Machek , Randy Dunlap , Stef van Os List-Id: devicetree@vger.kernel.org On 4/18/2018 6:59 AM, Rob Herring wrote: > On Tue, Apr 17, 2018 at 5:06 PM, Jae Hyun Yoo > 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 >>>> 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 > Thanks! I'll use 'clock-frequency' for it. Jae