Re: [PATCH 3/4] PM: EM: Add em_dev_update_chip_binning()

Christian Loehle
2024-03-14T14:32:22Z

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@arm.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.

> …