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

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Message-ID: <000b01d3f0f3$aa961cc0$ffc25640$@codeaurora.org>
Date:   Mon, 21 May 2018 14:05:41 +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

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?
> 
> > +	opp_silver =
> dev_pm_opp_set_supported_hw(cpu_dev_silver,&versions,1);
> > +	if (IS_ERR(opp_silver)) {
> > +		dev_err(cpu_dev_silver, "Failed to set supported
> hardware\n");
> > +		ret = PTR_ERR(opp_silver);
> > +		goto free_np;
> > +	}
> > +
> > +	opp_gold =
> dev_pm_opp_set_supported_hw(cpu_dev_gold,&versions,1);
> > +	if (IS_ERR(opp_gold)) {
> > +		dev_err(cpu_dev_gold, "Failed to set supported
> hardware\n");
> > +		ret = PTR_ERR(opp_gold);
> > +		goto free_opp_silver;
> > +	}
> 
> Given that cpu_dev_silver == cpu_dev_gold, doesn't the second call to
> dev_pm_opp_set_supported_hw() always fail, as opp_table-
> >supported_hw will be set by the first call?
> 
> To me, this driver looks completely useless as it will always fail to
initialise,
> and I question whether this code has even been runtime tested.
> 
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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