linux-kernel - RE: [PATCH] cpufreq: imx-cpufreq-dt: Assign max supported frequency as suspend frequency

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Message-ID: <AM6PR0402MB3911FD909B16941E22974FC6F5F10@AM6PR0402MB3911.eurprd04.prod.outlook.com>
Date:   Tue, 9 Jul 2019 07:24:28 +0000
From:   Anson Huang <anson.huang@....com>
To:     Leonard Crestez <leonard.crestez@....com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
CC:     "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: RE: [PATCH] cpufreq: imx-cpufreq-dt: Assign max supported frequency
 as suspend frequency


> > On 7/8/2019 10:55 AM, Anson.Huang@....com wrote:
> > > To reduce the suspend/resume latency, CPU's max supported frequency
> > > should be used during low level suspend/resume phase, "opp-suspend"
> > > property is NOT feasible since OPP defined in DT could be NOT
> > > supported according to speed garding and market segment fuse settings.
> > > So we can assign the cpufreq policy's suspend_freq with max
> > > available frequency provided by cpufreq driver.
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> >
> > > diff --git a/drivers/cpufreq/imx-cpufreq-dt.c
> > > b/drivers/cpufreq/imx-cpufreq-dt.c
> >
> > > +static int __init imx_cpufreq_dt_setup_suspend_opp(void)
> > > +{
> > > +	struct cpufreq_policy *policy = cpufreq_cpu_get(0);
> > > +
> > > +	policy->suspend_freq = cpufreq_quick_get_max(0);
> > > +
> > > +	return 0;
> > > +}
> > > +late_initcall(imx_cpufreq_dt_setup_suspend_opp);
> >
> > The imx-cpufreq-dt driver is built as a module by default and this
> > patch produces an error:
> >
> > In file included from ../drivers/cpufreq/imx-cpufreq-dt.c:11:
> > ../include/linux/module.h:131:42: error: redefinition of ‘__inittest’
> >    static inline initcall_t __maybe_unused __inittest(void)  \
> >                                            ^~~~~~~~~~
> > ../include/linux/device.h:1656:1: note: in expansion of macro ‘module_init’
> >   module_init(__driver##_init); \
> >   ^~~~~~~~~~~
> >
> > As far as I can tell late_initcall is not supported for modules.
> 
> Ah, yes, I have NOT test the module build, I ONLY tested the built-in case,
> thanks for reminder.
> 
> >
> > Viresh: "max freq as suspend freq" is something that could be useful
> > for other SOC families. The hardware can suspend at any freq; it's
> > just that the highest one makes sense because it makes suspend/resume
> slightly faster.
> 
> Agree.
> 
> >
> > Could this behavior be pushed to cpufreq-dt as a bool flag inside
> > struct cpufreq_dt_platform_data?
> >
> > Only a few other platforms use this, most others pass NULL like imx.
> > But passing custom SOC-specific flags to cpufreq-dt makes a lot of
> > sense
> 
> Although we have other methods to make it work for i.MX platforms, like
> setting the suspend freq as this patch did but ONLY be called before suspend,
> but if common cpufreq-dt can handle this case, that would benefit us and
> other platforms a lot, waiting for your opinion.

Please ignore this patch, based on the discussion, I have sent out a new patch
series to support this feature. Please review them:
https://patchwork.kernel.org/patch/11036505/

Thanks,
Anson