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

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Date:   Mon, 8 Jul 2019 11:04:01 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Anson Huang <anson.huang@....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.

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.

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

--
Regards,
Leonard