linux-kernel - Re: [PATCH 2/3] firmware: arm_scmi: Add support for marking certain frequencies as boost

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Date: Wed, 31 Jan 2024 16:08:48 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Pierre Gondois <pierre.gondois@....com>
Cc: Sibi Sankar <quic_sibis@...cinc.com>, cristian.marussi@....com,
	Sudeep Holla <sudeep.holla@....com>,
	linux-arm-kernel@...ts.infradead.org, sboyd@...nel.org,
	lukasz.luba@....com, dietmar.eggemann@....com,
	morten.rasmussen@....com, viresh.kumar@...aro.org,
	rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, quic_mdtipton@...cinc.com,
	linux-arm-msm@...r.kernel.org, nm@...com
Subject: Re: [PATCH 2/3] firmware: arm_scmi: Add support for marking certain
 frequencies as boost

On Wed, Jan 31, 2024 at 03:29:43PM +0100, Pierre Gondois wrote:
> Hello Sibi,
> 
> On 1/17/24 12:04, Sibi Sankar wrote:
> > All opps above the sustained level/frequency are treated as boost, so mark
> > them accordingly.
> > 
> > Suggested-by: Sudeep Holla <sudeep.holla@....com>
> > Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
> > ---
> >   drivers/firmware/arm_scmi/perf.c | 11 ++++++++++-
> >   1 file changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> > index e286f04ee6e3..d3fb8c804b3d 100644
> > --- a/drivers/firmware/arm_scmi/perf.c
> > +++ b/drivers/firmware/arm_scmi/perf.c
> > @@ -811,7 +811,7 @@ static int scmi_dvfs_device_opps_add(const struct scmi_protocol_handle *ph,
> >   				     struct device *dev, u32 domain)
> >   {
> >   	int idx, ret;
> > -	unsigned long freq;
> > +	unsigned long freq, sustained_freq;
> >   	struct dev_pm_opp_data data = {};
> >   	struct perf_dom_info *dom;
> > @@ -819,12 +819,21 @@ static int scmi_dvfs_device_opps_add(const struct scmi_protocol_handle *ph,
> >   	if (IS_ERR(dom))
> >   		return PTR_ERR(dom);
> > +	if (!dom->level_indexing_mode)
> > +		sustained_freq = dom->sustained_perf_level * dom->mult_factor;
> > +	else
> > +		sustained_freq = dom->sustained_freq_khz * dom->mult_factor;
> > +
> >   	for (idx = 0; idx < dom->opp_count; idx++) {
> >   		if (!dom->level_indexing_mode)
> >   			freq = dom->opp[idx].perf * dom->mult_factor;
> >   		else
> >   			freq = dom->opp[idx].indicative_freq * dom->mult_factor;
> > +		/* All opps above the sustained level/frequency are treated as boost */
> > +		if (sustained_freq && freq > sustained_freq)
>
> It seems the sustained_freq is not optional since SCMI v1.0,
> is it necessary to check that (sustained_freq != 0) ?
>

Technically correct, we don't have to. But since day 1, we checked and
handled 0 for perf_level specifically to avoid division by zero. I am
just worried if there are any platforms in the wild with these values as
0. We can start without the check and add it if someone complains perhaps ?

-- 
Regards,
Sudeep