linux-kernel - RE: [PATCH] cpufreq: Add Kryo CPU scaling driver

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Date:   Mon, 21 May 2018 15:35:07 +0300
From:   <ilialin@...eaurora.org>
To:     "'Russell King - ARM Linux'" <linux@...linux.org.uk>
Cc:     <viresh.kumar@...aro.org>, <devicetree@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-soc@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] cpufreq: Add Kryo CPU scaling driver

There are 2 CPU clusters in the Kryo, CPU 0 and 1 are called Silver Cluster
and CPU 2 and 3 - Gold Cluster. Each cluster has single clock. The clusters
differ in terms of speed capabilities, computing power and power
consumption. Therefore, I define separate OPP table for each cluster, and my
driver will choose the appropriate OPP subset for each cluster.
Lead refers to first CPU in the cluster.

> -----Original Message-----
> From: Russell King - ARM Linux <linux@...linux.org.uk>
> Sent: Monday, May 21, 2018 15:12
> To: ilialin@...eaurora.org
> Cc: viresh.kumar@...aro.org; devicetree@...r.kernel.org; linux-
> pm@...r.kernel.org; linux-arm-msm@...r.kernel.org; linux-
> kernel@...r.kernel.org; linux-soc@...r.kernel.org; linux-
> clk@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
> Subject: Re: [PATCH] cpufreq: Add Kryo CPU scaling driver
> 
> On Mon, May 21, 2018 at 02:05:41PM +0300, ilialin@...eaurora.org wrote:
> > You are right.
> > cpu_dev_silver != cpu_dev_gold, and I found this with my tests as well.
> > Thank you.
> >
> > > -----Original Message-----
> > > From: Russell King - ARM Linux <linux@...linux.org.uk>
> > > Sent: Monday, May 21, 2018 13:54
> > > To: Ilia Lin <ilialin@...eaurora.org>
> > > Cc: viresh.kumar@...aro.org; devicetree@...r.kernel.org; linux-
> > > pm@...r.kernel.org; linux-arm-msm@...r.kernel.org; linux-
> > > kernel@...r.kernel.org; linux-soc@...r.kernel.org; linux-
> > > clk@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
> > > Subject: Re: [PATCH] cpufreq: Add Kryo CPU scaling driver
> > >
> > > On Mon, May 21, 2018 at 01:31:30PM +0300, Ilia Lin wrote:
> > > > +#define SILVER_LEAD	0
> > > > +#define GOLD_LEAD	2
> > >
> > > Okay, two different values here, but "GOLD_LEAD" appears unused.
> > >
> > > > +	cpu_dev_silver = get_cpu_device(SILVER_LEAD);
> > > > +	if (NULL == cpu_dev_silver)
> > > > +		return -ENODEV;
> > > > +
> > > > +	cpu_dev_gold = get_cpu_device(SILVER_LEAD);
> > > > +	if (NULL == cpu_dev_gold)
> > > > +		return -ENODEV;
> > >
> > > get_cpu_device() takes the logical CPU number.  So the above gets
> > > CPU 0 each time, and so cpu_dev_silver == cpu_dev_gold here.  So
> > > what's the point of the second get_cpu_device() ?  If it's supposed to
be:
> > >
> > > 	cpu_dev_gold = get_cpu_device(GOLD_LEAD);
> > >
> > > That would get CPU 2, but in terms of these defines, it doesn't make
> > > that much sense.  What exactly does "silver lead" and "gold lead"
> > > refer to in
> > these
> > > definitions?
> 
> I think you still need to explain this.
> 
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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