Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 268622184A
MIME-Version: 1.0
In-Reply-To: <6ff697e8-cd20-e551-da13-b614cc39f900@linux.intel.com>
References: <20180410183212.16787-1-jae.hyun.yoo@linux.intel.com>
 <20180410183212.16787-8-jae.hyun.yoo@linux.intel.com> <20180416181423.t4vf7sugv6z3aw5h@rob-hp-laptop>
 <aee4e04c-885f-b1d8-9e85-9e741551342f@linux.intel.com> <287e0fd9-b631-2602-2785-7b8aaed7a6b9@linux.intel.com>
 <6ff697e8-cd20-e551-da13-b614cc39f900@linux.intel.com>
From:   Rob Herring <robh@kernel.org>
Date:   Wed, 18 Apr 2018 09:32:36 -0500
Message-ID: <CAL_JsqLcxEnCOywTtU14G4=6A5m6G=KH3oi8m1VxKSEdxuv-ww@mail.gmail.com>
Subject: Re: [PATCH v3 07/10] Documentation: dt-bindings: Add documents for
 PECI hwmon client drivers
To:     Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Cc:     Alan Cox <alan@linux.intel.com>, Andrew Jeffery <andrew@aj.id.au>,
        Andrew Lunn <andrew@lunn.ch>,
        Andy Shevchenko <andriy.shevchenko@intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Fengguang Wu <fengguang.wu@intel.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Haiyue Wang <haiyue.wang@linux.intel.com>,
        James Feist <james.feist@linux.intel.com>,
        Jason M Biils <jason.m.bills@linux.intel.com>,
        Jean Delvare <jdelvare@suse.com>,
        Joel Stanley <joel@jms.id.au>,
        Julia Cartwright <juliac@eso.teric.us>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Milton Miller II <miltonm@us.ibm.com>,
        Pavel Machek <pavel@ucw.cz>,
        Randy Dunlap <rdunlap@infradead.org>,
        Stef van Os <stef.van.os@prodrive-technologies.com>,
        Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>,
        Vernon Mauery <vernon.mauery@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-doc@vger.kernel.org, devicetree@vger.kernel.org,
        Linux HWMON List <linux-hwmon@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        OpenBMC Maillist <openbmc@lists.ozlabs.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Apr 17, 2018 at 3:40 PM, Jae Hyun Yoo
<jae.hyun.yoo@linux.intel.com> wrote:
> On 4/16/2018 4:51 PM, Jae Hyun Yoo wrote:
>>
>> On 4/16/2018 4:22 PM, Jae Hyun Yoo wrote:
>>>
>>> On 4/16/2018 11:14 AM, Rob Herring wrote:
>>>>
>>>> On Tue, Apr 10, 2018 at 11:32:09AM -0700, Jae Hyun Yoo wrote:
>>>>>
>>>>> This commit adds dt-bindings documents for PECI cputemp and dimmtemp
>>>>> client
>>>>> drivers.
>>>>
>>>>
>
> [...]
>
>>>>> +Example:
>>>>> +    peci-bus@0 {
>>>>> +        #address-cells = <1>;
>>>>> +        #size-cells = <0>;
>>>>> +        < more properties >
>>>>> +
>>>>> +        peci-dimmtemp@cpu0 {
>>>>
>>>>
>>>> unit-address is wrong.
>>>>
>>>
>>> Will fix it using the reg value.
>>>
>>>> It is a different bus from cputemp? Otherwise, you have conflicting
>>>> addresses. If that's the case, probably should make it clear by showing
>>>> different host adapters for each example.
>>>>
>>>
>>> It could be the same bus with cputemp. Also, client address sharing is
>>> possible by PECI core if the functionality is different. I mean, cputemp and
>>> dimmtemp targeting the same client is possible case like this.
>>> peci-cputemp@30
>>> peci-dimmtemp@30
>>>
>>
>> Oh, I got your point. Probably, I should change these separate settings
>> into one like
>>
>> peci-client@30 {
>>      compatible = "intel,peci-client";
>>      reg = <0x30>;
>> };
>>
>> Then cputemp and dimmtemp drivers could refer the same compatible string.
>> Will rewrite it.
>>
>
> I've checked it again and realized that it should use function based node
> name like:
>
> peci-cputemp@30
> peci-dimmtemp@30
>
> If it use the same string like 'peci-client@30', the drivers cannot be
> selectively enabled. The client address sharing way is well handled in PECI
> core and this way would be better for the future implementations of other
> PECI functional drivers such as crash dump driver and so on. So I'm going
> change the unit-address only.

2 nodes at the same address is wrong (and soon dtc will warn you on
this). You have 2 potential options. The first is you need additional
address information in the DT if these are in fact 2 independent
devices. This could be something like a function number to use
something from PCI addressing. From what I found on PECI, it doesn't
seem to have anything like that. The 2nd option is you have a single
DT node which registers multiple hwmon devices. DT nodes and drivers
don't have to be 1-1. Don't design your DT nodes from how you want to
partition drivers in some OS.

Rob