On Tue, May 22, 2018 at 12:18 PM, Jae Hyun Yoo
<jae.hyun.yoo@xxxxxxxxxxxxxxx> wrote:
> On 5/22/2018 9:42 AM, Rob Herring wrote:
>>
>> On Mon, May 21, 2018 at 12:59:05PM -0700, Jae Hyun Yoo wrote:
>>>
>>> This commit adds dt-bindings documents for PECI hwmon client drivers.
>>>
>>> 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: Andrew Jeffery <andrew@xxxxxxxx>
>>> Cc: Arnd Bergmann <arnd@xxxxxxxx>
>>> Cc: Jason M Biils <jason.m.bills@xxxxxxxxxxxxxxx>
>>> Cc: Joel Stanley <joel@xxxxxxxxx>
>>> ---
>>> .../bindings/hwmon/peci-cputemp.txt | 23 ++++++++++++++++++
>>> .../bindings/hwmon/peci-dimmtemp.txt | 24 +++++++++++++++++++
>>> 2 files changed, 47 insertions(+)
>>> create mode 100644
>>> Documentation/devicetree/bindings/hwmon/peci-cputemp.txt
>>> create mode 100644
>>> Documentation/devicetree/bindings/hwmon/peci-dimmtemp.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/hwmon/peci-cputemp.txt
>>> b/Documentation/devicetree/bindings/hwmon/peci-cputemp.txt
>>> new file mode 100644
>>> index 000000000000..2f59aee12d9e
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/hwmon/peci-cputemp.txt
>>> @@ -0,0 +1,23 @@
>>> +Bindings for Intel PECI (Platform Environment Control Interface) cputemp
>>> driver.
>>> +
>>> +Required properties:
>>> +- compatible : Should be "intel,peci-cputemp".
>>> +- reg : Should contain address of a client CPU. Address range of
>>> CPU
>>> + clients is starting from 0x30 based on PECI specification.
>>> +
>>> +Example:
>>> + peci-bus@0 {
>>> + #address-cells = <1>;
>>> + #size-cells = <0>;
>>> + < more properties >
>>> +
>>> + peci-cputemp@30 {
>>> + compatible = "intel,peci-cputemp";
>>> + reg = <0x30>;
>>> + };
>>
>>
>> [...]
>>
>>> + peci-dimmtemp@30 {
>>> + compatible = "intel,peci-dimmtemp";
>>> + reg = <0x30>;
>>> + };
>>
>>
>> As I said in the prior version, 2 nodes at the same address is wrong.
>>
>> Rob
>>
>
> In PECI bus, there is one and only bus host (adapter) and multiple
> clients on a PECI bus, and PECI spec doesn't allow multiple originators
> so only the host device can originate message.
Yes, I get that. A single host still has to address slave devices.
> In this implementation,
> all message transactions on a bus from client driver modules and user
> space will be serialized well in the PECI core bus driver so bus
> occupation and traffic arbitration will be managed well in the PECI core
> bus driver even in case of a bus has 2 client drivers at the same
> address. I'm sure that this implementation doesn't make that kind of
> problem to OS.
Multiple clients to a single device is common, but that is a software
problem and doesn't belong in DT.
I don't think there is a single other case in the kernel where
multiple drivers can bind to the same device at a given bus address.
That is why we have things like MFD. Though in this case, why can't
one hwmon driver register multiple hwmon devices (cpu and dimm temps)?
Rob
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