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

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Date: Thu, 14 Mar 2024 14:32:17 +0000
From: Christian Loehle <christian.loehle@....com>
To: Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Cc: dietmar.eggemann@....com, 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()

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.

> [...]