linux-kernel - Re: [PATCH 0/3] Add support to disable sensor groups in P9

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Message-ID: <56bba97b-c6ee-e7a1-136c-a2236437484a@roeck-us.net>
Date:   Thu, 17 May 2018 05:38:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Cc:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        stewart@...ux.vnet.ibm.com
Subject: Re: [PATCH 0/3] Add support to disable sensor groups in P9

On 05/16/2018 11:10 PM, Shilpasri G Bhat wrote:
> 
> 
> On 05/15/2018 08:32 PM, Guenter Roeck wrote:
>> On Thu, Mar 22, 2018 at 04:24:32PM +0530, Shilpasri G Bhat wrote:
>>> This patch series adds support to enable/disable OCC based
>>> inband-sensor groups at runtime. The environmental sensor groups are
>>> managed in HWMON and the remaining platform specific sensor groups are
>>> managed in /sys/firmware/opal.
>>>
>>> The firmware changes required for this patch is posted below:
>>> https://lists.ozlabs.org/pipermail/skiboot/2018-March/010812.html
>>>
>>
>> Sorry for not getting back earlier. This is a tough one.
>>
> 
> Thanks for the reply. I have tried to answer your questions according to my
> understanding below:
> 
>> Key problem is that you are changing the ABI with those new attributes.
>> On top of that, the attributes _do_ make some sense (many chips support
>> enabling/disabling of individual sensors), suggesting that those or
>> similar attributes may or even should at some point be added to the ABI.
>>
>> At the same time, returning "0" as measurement values when sensors are
>> disabled does not seem like a good idea, since "0" is a perfectly valid
>> measurement, at least for most sensors.
> 
> I agree.
> 
>>
>> Given that, we need to have a discussion about adding _enable attributes to
>> the ABI
> 
>> what is the scope,
> IIUC the scope should be RW and the attribute is defined for each supported
> sensor group
> 

That is _your_ need. I am not aware of any other chip where a per-sensor group
attribute would make sense. The discussion we need has to extend beyond the need
of a single chip.

Guenter

>> when should the attributes exist and when not,
> We control this currently via device-tree
> 
>> do we want/need power_enable or powerX_enable or both, and so on), and
> We need power_enable right now
> 
>> what to return if a sensor is disabled (such as -ENODATA).
> -ENODATA sounds good.
> 
> Thanks and Regards,
> Shilpa
> 
>   Once we have an
>> agreement, we can continue with an implementation.
>>
>> Guenter
>>
>>> Shilpasri G Bhat (3):
>>>    powernv:opal-sensor-groups: Add support to enable sensor groups
>>>    hwmon: ibmpowernv: Add attributes to enable/disable sensor groups
>>>    powernv: opal-sensor-groups: Add attributes to disable/enable sensors
>>>
>>>   .../ABI/testing/sysfs-firmware-opal-sensor-groups  |  34 ++++++
>>>   Documentation/hwmon/ibmpowernv                     |  31 ++++-
>>>   arch/powerpc/include/asm/opal-api.h                |   4 +-
>>>   arch/powerpc/include/asm/opal.h                    |   2 +
>>>   .../powerpc/platforms/powernv/opal-sensor-groups.c | 104 ++++++++++++-----
>>>   arch/powerpc/platforms/powernv/opal-wrappers.S     |   1 +
>>>   drivers/hwmon/ibmpowernv.c                         | 127 +++++++++++++++++++--
>>>   7 files changed, 265 insertions(+), 38 deletions(-)
>>>   create mode 100644 Documentation/ABI/testing/sysfs-firmware-opal-sensor-groups
>>>
>>> -- 
>>> 1.8.3.1
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in
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>>
> 
>