Re: [PATCHv9 02/20] thermal: introduce device tree parser

From: Wei Ni
Date: Mon Jan 06 2014 - 21:44:40 EST

On 01/06/2014 10:54 PM, Eduardo Valentin wrote:
> * PGP Signed by an unknown key
> On 06-01-2014 09:51, Mark Rutland wrote:
>> On Thu, Jan 02, 2014 at 05:50:06PM +0000, Matthew Longnecker wrote:
>>>> I think the platform driver may set governor for the thermal zone,
>>>> so how about to add a property named as "governor",
>>>> and parse it to tzp->governor_name,
>>>> something like:
>>>> ret = of_property_read_string(child, "governor", &str);
>>>> if (ret == 0)
>>>> if (strlen(str) < THERMAL_NAME_LENGTH)
>>>> strcpy(tzp->governor_name, str);
>>>> Thanks.
>>>> Wei.
>>> DT is supposed to describe the hardware, right? The governor isn't
>>> hardware -- it's a software control policy. On the other hand, that
>>> control policy must be tuned according to the behaviors of the platform
>>> hardware otherwise the system will be unstable.
>>> Is it appropriate to be naming the governor in DT? If so, is it equally
>>> appropriate to describe any governor-specific parameters in DT (even
>>> though they are pure software constructs)?
>> The dt should be relatively static -- if the hardware doesn't change the
>> dt shouldn't have to.
>> The governers are not static. We can introduce new ones and throw away
>> old ones at any time. Tuning parameters can also change at any time.
>> I'd prefer to not have governer details described in the dt, and the
>> choice of governer and configuration of its tuning parameters should be
>> made at runtime somehow.
> Agreed.

Yes, I think so, but the of-thermal driver handle the
thermal_zone_device_register, and pass the "tzp" without governor_name,
so the created thermal_zone's governor will be NULL, then it can't run
into the governor->throttle() if needed. And currently there have no
interface to support updating governor and configuration at runtime.
I think it's better to initialize the governor_name when register the
thermal zone device in the of-thermal driver.


>> Thanks,
>> Mark.

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