linux-kernel - Re: [PATCH 3/4] PM: EM: Add em_dev_update_chip

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Date: Fri, 22 Mar 2024 10:26:31 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Christian Loehle <christian.loehle@....com>
Cc: dietmar.eggemann@....com, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 sboyd@...nel.org, nm@...com, linux-samsung-soc@...r.kernel.org,
 daniel.lezcano@...aro.org, rafael@...nel.org, viresh.kumar@...aro.org,
 krzysztof.kozlowski@...aro.org, alim.akhtar@...sung.com,
 m.szyprowski@...sung.com, mhiramat@...nel.org
Subject: Re: [PATCH 3/4] PM: EM: Add em_dev_update_chip_binning()

Hi Christian,

On 3/14/24 14:32, Christian Loehle wrote:
> On 14/03/2024 14:04, Lukasz Luba wrote:
>> Add a function which allows to modify easily the EM after the new voltage
>> information is available. The device drivers for the chip can adjust
>> the voltage values after setup. The voltage for the same frequency in OPP
>> can be different due to chip binning. The voltage impacts the power usage
>> and the EM power values can be updated to reflect that.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
>> ---
>>   include/linux/energy_model.h |  5 ++++
>>   kernel/power/energy_model.c  | 51 ++++++++++++++++++++++++++++++++++++
>>   2 files changed, 56 insertions(+)
>>
>> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
>> index 770755df852f1..d30d67c2f07cf 100644
>> --- a/include/linux/energy_model.h
>> +++ b/include/linux/energy_model.h
>> @@ -172,6 +172,7 @@ struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd);
>>   void em_table_free(struct em_perf_table __rcu *table);
>>   int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
>>   			 int nr_states);
>> +int em_dev_update_chip_binning(struct device *dev);
>>   
>>   /**
>>    * em_pd_get_efficient_state() - Get an efficient performance state from the EM
>> @@ -387,6 +388,10 @@ int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
>>   {
>>   	return -EINVAL;
>>   }
>> +static inline int em_dev_update_chip_binning(struct device *dev)
>> +{
>> +	return -EINVAL;
>> +}
>>   #endif
>>   
>>   #endif
>> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
>> index 6960dd7393b2d..1494a909844a4 100644
>> --- a/kernel/power/energy_model.c
>> +++ b/kernel/power/energy_model.c
>> @@ -808,3 +808,54 @@ static void em_update_workfn(struct work_struct *work)
>>   {
>>   	em_check_capacity_update();
>>   }
>> +
>> +/**
>> + * em_dev_update_chip_binning() - Update Energy Model with new values after
>> + *			the new voltage information is present in the OPPs.
>> + * @dev		: Device for which the Energy Model has to be updated.
>> + *
>> + * This function allows to update easily the EM with new values available in
>> + * the OPP framework and DT. It can be used after the chip has been properly
>> + * verified by device drivers and the voltages adjusted for the 'chip binning'.
>> + * It uses the "dynamic-power-coefficient" DT property to calculate the power
>> + * values for EM. For power calculation it uses the new adjusted voltage
>> + * values known for OPPs, which might be changed after boot.
>> + */
>> +int em_dev_update_chip_binning(struct device *dev)
>> +{
>> +	struct em_perf_table __rcu *em_table;
>> +	struct em_perf_domain *pd;
>> +	int i, ret;
>> +
>> +	if (IS_ERR_OR_NULL(dev))
>> +		return -EINVAL;
>> +
>> +	pd = em_pd_get(dev);
>> +	if (!pd) {
>> +		dev_warn(dev, "Couldn't find Energy Model %d\n", ret);
> 
> ret is uninitialized at this point, I guess just
> +		dev_warn(dev, "Couldn't find Energy Model\n");
> already contains everything relevant.
> 

Good catch, thanks! Yes, I agree it contains enough. I'm going
to send v2 with this.

Regards,
Lukasz