linux-kernel - Re: [PATCH v2] firmware: arm_scmi: add a getter for power of performance states

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180910160638.GA14835@e107155-lin>
Date:   Mon, 10 Sep 2018 17:06:38 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Quentin Perret <quentin.perret@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v2] firmware: arm_scmi: add a getter for power of
 performance states

On Mon, Sep 03, 2018 at 11:24:39AM +0100, Quentin Perret wrote:
> The SCMI protocol can be used to get power estimates from firmware
> corresponding to each performance state of a device. Although these power
> costs are already managed by the SCMI firmware driver, they are not
> exposed to any external subsystem yet.
> 
> Fix this by adding a new get_power() interface to the exisiting perf_ops
> defined for the SCMI protocol.
> 
> Signed-off-by: Quentin Perret <quentin.perret@....com>
> ---
> v2: rebased on 4.19-rc2
> ---
>  drivers/firmware/arm_scmi/perf.c | 28 ++++++++++++++++++++++++++++
>  include/linux/scmi_protocol.h    |  4 ++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index 721e6c57beae..272abd2cb3f0 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -421,6 +421,33 @@ static int scmi_dvfs_freq_get(const struct scmi_handle *handle, u32 domain,
>  	return ret;
>  }
>  
> +static int scmi_dvfs_power_get(const struct scmi_handle *handle, u32 domain,
> +			       unsigned long *freq, unsigned long *power)

I feel the name "power_get" gives me feeling that it refers to instant
power than the computed value. At least in scmi interface, freq_get
provides current value of running frequency. I am not sure of the
consistency in the naming in other subsystems.

Does it makes sense to name it "scmi_dvfs_est_power_get" as it actually
refers to estimated power cost ?

> +{
> +	struct scmi_perf_info *pi = handle->perf_priv;
> +	struct perf_dom_info *dom;
> +	unsigned long opp_freq;
> +	int idx, ret = -EINVAL;
> +	struct scmi_opp *opp;
> +
> +	dom = pi->dom_info + domain;
> +	if (!dom)
> +		return -EIO;
> +
> +	for (opp = dom->opp, idx = 0; idx < dom->opp_count; idx++, opp++) {
> +		opp_freq = opp->perf * dom->mult_factor;
> +		if (opp_freq < *freq)
> +			continue;
> +
> +		*freq = opp_freq;
> +		*power = opp->power;
> +		ret = 0;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>  static struct scmi_perf_ops perf_ops = {
>  	.limits_set = scmi_perf_limits_set,
>  	.limits_get = scmi_perf_limits_get,
> @@ -431,6 +458,7 @@ static struct scmi_perf_ops perf_ops = {
>  	.device_opps_add = scmi_dvfs_device_opps_add,
>  	.freq_set = scmi_dvfs_freq_set,
>  	.freq_get = scmi_dvfs_freq_get,
> +	.power_get = scmi_dvfs_power_get,

same here s/.power_get/.est_power_get/

>  };
>  
>  static int scmi_perf_protocol_init(struct scmi_handle *handle)
> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index f4c9fc0fc755..2ecbd2c5a249 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h
> @@ -91,6 +91,8 @@ struct scmi_clk_ops {
>   *	to sustained performance level mapping
>   * @freq_get: gets the frequency for a given device using sustained frequency
>   *	to sustained performance level mapping
> + * @power_get: gets the power dissipated for a given performance domain at a

s/power dissipated/estimated power cost/

--
Regards,
Sudeep