Re: [PATCH v2 3/4] lib/power: add get and set API for scaling freq min and max with pstate mode

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 19-Apr-22 12:25 PM, Kevin Laatz wrote:
> Add new get/set API to allow the user or application to set the minimum
> and maximum frequencies to use when scaling.
> Previously, the frequency range was determined by the HW capabilities of
> the CPU. With this new API, the user or application can constrain this
> if required.
> 
> Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
> ---

<snip>

>   
> +int
> +rte_power_pmd_mgmt_set_scaling_freq_min(unsigned int lcore, unsigned int min)
> +{
> +	if (lcore >= RTE_MAX_LCORE) {
> +		RTE_LOG(ERR, POWER, "Invalid lcore ID: %u\n", lcore);
> +		rte_errno = EINVAL;
> +		return -1;
> +	}
> +	scale_freq_min[lcore] = min;

Are there any constraints on the value ranges, or are we just going to 
accept any and all values? If the idea was to allow valid values plus 
some special "default" value, you can still restrict the range, but 
allow 0 as a special case?

> +
> +	return 0;
> +}
> +
> +int
> +rte_power_pmd_mgmt_set_scaling_freq_max(unsigned int lcore, unsigned int max)
> +{
> +	if (lcore >= RTE_MAX_LCORE) {
> +		RTE_LOG(ERR, POWER, "Invalid lcore ID: %u\n", lcore);
> +		rte_errno = EINVAL;
> +		return -1;
> +	}
> +	scale_freq_max[lcore] = max;

Same as above. Also, do we want UINT32_MAX be the "special" value for 
the "max" case? What do you think of having "0" as "not set", but maybe 
set it internally to UINT32_MAX if you still want to keep using the 
RTE_MIN/MAX macros?

> +
> +	return 0;
> +}
> +
> +int
> +rte_power_pmd_mgmt_get_scaling_freq_min(unsigned int lcore)
> +{

<snip>

> diff --git a/lib/power/rte_power_pmd_mgmt.h b/lib/power/rte_power_pmd_mgmt.h
> index 18a9c3abb5..74e3fa710b 100644
> --- a/lib/power/rte_power_pmd_mgmt.h
> +++ b/lib/power/rte_power_pmd_mgmt.h
> @@ -148,6 +148,86 @@ __rte_experimental
>   unsigned int
>   rte_power_pmd_mgmt_get_pause_duration(void);
>   
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change, or be removed, without prior notice.
> + *
> + * Set the min frequency to be used for frequency scaling.
> + *
> + * @note Supported by: Pstate mode.
> + *
> + * @param lcore
> + *   The ID of the lcore to set the min frequency for.
> + * @param min
> + *   The value, in Hertz, to set the minimum frequency to.

Is it really in Hertz? As far as I can tell, it's in steps of 100MHz 
(BUS_FREQ).

-- 
Thanks,
Anatoly