Re: [PATCH v2 1/2] PM / devfreq: Add PM QoS support

From: Matthias Kaehlcke <mka@chromium.org>
To: Leonard Crestez <leonard.crestez@nxp.com>
Cc: "Artur Świgoń" <a.swigon@partner.samsung.com>,
	"Jacky Bai" <ping.bai@nxp.com>,
	linux-pm@vger.kernel.org,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"Chanwoo Choi" <cw00.choi@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"MyungJoo Ham" <myungjoo.ham@samsung.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Georgi Djakov" <georgi.djakov@linaro.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/2] PM / devfreq: Add PM QoS support
Date: Thu, 5 Dec 2019 09:48:46 -0800	[thread overview]
Message-ID: <20191205174846.GM228856@google.com> (raw)
In-Reply-To: <eaef2de34fed598a1b6ffecc9010e281c6f36318.1575540224.git.leonard.crestez@nxp.com>

On Thu, Dec 05, 2019 at 12:05:06PM +0200, Leonard Crestez wrote:
> Register notifiers with the PM QoS framework in order to respond to
> requests for DEV_PM_QOS_MIN_FREQUENCY and DEV_PM_QOS_MAX_FREQUENCY.
> 
> No notifiers are added by this patch but PM QoS constraints can be
> imposed externally (for example from other devices).
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 77 +++++++++++++++++++++++++++++++++++++++
>  include/linux/devfreq.h   |  5 +++
>  2 files changed, 82 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index bdeb4189c978..e8b943fc4259 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -22,15 +22,18 @@
>  #include <linux/platform_device.h>
>  #include <linux/list.h>
>  #include <linux/printk.h>
>  #include <linux/hrtimer.h>
>  #include <linux/of.h>
> +#include <linux/pm_qos.h>
>  #include "governor.h"
>  
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/devfreq.h>
>  
> +#define HZ_PER_KHZ	1000
> +
>  static struct class *devfreq_class;
>  
>  /*
>   * devfreq core provides delayed work based load monitoring helper
>   * functions. Governors can use these or can implement their own
> @@ -109,10 +112,11 @@ static unsigned long find_available_max_freq(struct devfreq *devfreq)
>  static void get_freq_range(struct devfreq *devfreq,
>  			   unsigned long *min_freq,
>  			   unsigned long *max_freq)
>  {
>  	unsigned long *freq_table = devfreq->profile->freq_table;
> +	s32 qos_min_freq, qos_max_freq;
>  
>  	lockdep_assert_held(&devfreq->lock);
>  
>  	/*
>  	 * Initialize minimum/maximum frequency from freq table.
> @@ -125,10 +129,20 @@ static void get_freq_range(struct devfreq *devfreq,
>  	} else {
>  		*min_freq = freq_table[devfreq->profile->max_state - 1];
>  		*max_freq = freq_table[0];
>  	}
>  
> +	/* Apply constraints from PM QoS */
> +	qos_min_freq = dev_pm_qos_read_value(devfreq->dev.parent,
> +					     DEV_PM_QOS_MIN_FREQUENCY);
> +	qos_max_freq = dev_pm_qos_read_value(devfreq->dev.parent,
> +					     DEV_PM_QOS_MAX_FREQUENCY);
> +	*min_freq = max(*min_freq, (unsigned long)HZ_PER_KHZ * qos_min_freq);
> +	if (qos_max_freq != PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE)

The condition shouldn't be needed anymore now that
PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE is S32_MAX and not -1.

> +		*max_freq = min(*max_freq,
> +				(unsigned long)HZ_PER_KHZ * qos_max_freq);
> +

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>

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