Subject: Re: [PATCH v7 5/6] PM / devfreq: Add PM QoS support

From: Matthias Kaehlcke <[email-masked]>
Date: Mon, 23 Sep 2019 14:42:07 -0700

On Tue, Sep 24, 2019 at 12:10:33AM +0300, 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 <[email-masked]>
> ---
>  drivers/devfreq/devfreq.c | 76 +++++++++++++++++++++++++++++++++++++++
>  include/linux/devfreq.h   |  5 +++
>  2 files changed, 81 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 7f152a582e78..9887408f23bb 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -22,17 +22,20 @@
>  #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 HZ_PER_KHZ 1000
>  
>  #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
> @@ -123,10 +126,16 @@ static void devfreq_get_freq_range(struct devfreq *devfreq,
>  	} else {
>  		*min_freq = freq_table[devfreq->profile->max_state - 1];
>  		*max_freq = freq_table[0];
>  	}
>  
> +	/* constraints from PM QoS */
> +	*min_freq = max(*min_freq, HZ_PER_KHZ * (unsigned long)dev_pm_qos_read_value(
> +				devfreq->dev.parent, DEV_PM_QOS_MIN_FREQUENCY));
> +	*max_freq = min(*max_freq, HZ_PER_KHZ * (unsigned long)dev_pm_qos_read_value(
> +				devfreq->dev.parent, DEV_PM_QOS_MAX_FREQUENCY));
> +
>  	/* constraints from sysfs */
>  	*min_freq = max(*min_freq, devfreq->min_freq);
>  	*max_freq = min(*max_freq, devfreq->max_freq);
>  
>  	/* constraints from OPP interface */
> @@ -605,10 +614,53 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
>  	mutex_unlock(&devfreq->lock);
>  
>  	return ret;
>  }
>  
> +/**
> + * devfreq_qos_notifier_call() - Common handler for QoS constraints.
> + * @devfreq:    the devfreq instance.
> + */
> +static int devfreq_qos_notifier_call(struct devfreq *devfreq)
> +{
> +	int err;
> +
> +	mutex_lock(&devfreq->lock);
> +	err = update_devfreq(devfreq);
> +	mutex_unlock(&devfreq->lock);
> +	if (err)
> +		dev_err(&devfreq->dev, "dvfs for QoS constraints"
> +				" failed with (%d) error\n", err);

nit: DVFS. devfreq_monitor() also uses the lower-case acronym though, so
you can claim this is consistent :)

I'd prefer to spare you another trivial re-spin, but unfortunately
breaking the log message into multiple lines is a coding style
violation:

Documentation/process/coding-style.rst
  2) Breaking long lines and strings

  However, never break user-visible strings such as printk messages,
  because that breaks the ability to grep for them.

With that fixed:

Reviewed-by: Matthias Kaehlcke <[email-masked]>

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