Re: [PATCH] devfreq: do not ignore errors during store min, max frequency

[Lukasz Luba <lukasz.luba@arm.com>]

Hi MyungJoo,

On 27/04/17 09:30, MyungJoo Ham wrote:
>> This patch adds functionality to make sure when a call to set a new
>> max or min frequency is possible.
>> If storing the new value was not possible, restore previous one
>> and forward the error value.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
>> ---
>> It is based on v4.11-rc8.
>>
>>  drivers/devfreq/devfreq.c | 36 ++++++++++++++++++++++++++++++++----
>>  1 file changed, 32 insertions(+), 4 deletions(-)
>
> ...
>
>> +	ret = devfreq_get_freq_level(df, value);
>> +	if (ret < 0) {
>> +		dev_warn(dev, "Storing min freq failed with (%d) error\n", ret);
>> +		goto unlock;
>> +	}
>> +
>
> This is not good.
>
> For a device that supports [ 100, 400, 800, 1000 ] MHz,
> saying "min = 200 Mhz" or "max = 600 MHz" shouldn't be prohibited.
>
> Those functions are to express lower bound and upper bound, not to
> designate the exact operating frequencies.

Would it be possible to convince you to store a
'posible/valid frequency' (from OPP) in that value?
Governors (like simpleondemand) and drivers use it with the flags.
It would be useful for thermal subsystem. It could have the max/min for 
the devfreq device.

I could prepare a patch which sets the freq from OPP respecting
rounding up/down based on 'devfreq_recommended_opp()'.

Regards,
Lukasz