linux-kernel - RE: [PATCH v3 1/8] PM / devfreq: Set min/max

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Date:   Wed, 11 Oct 2017 11:09:52 +0000
From:   MyungJoo Ham <myungjoo.ham@...sung.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>
CC:     "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "chanwoo@...nel.org" <chanwoo@...nel.org>,
        Inki Dae <inki.dae@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH v3 1/8] PM / devfreq: Set min/max_freq when adding the
 devfreq device

> Prior to that, the min/max_freq of the devfreq device are always zero
> before the user changes the min/max_freq through sysfs entries.
> It might make the confusion for the min/max_freq.
> 
> This patch initializes the available min/max_freq by using the OPP
> during adding the devfreq device.
> 
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
>  drivers/devfreq/devfreq.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index a1c4ee818614..ae8717a6eee1 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index a1c4ee818614..ae8717a6eee1 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -69,6 +69,34 @@ static struct devfreq *find_device_devfreq(struct device *dev)
>  	return ERR_PTR(-ENODEV);
>  }
>  
> +static unsigned long find_available_min_freq(struct devfreq *devfreq)
> +{
> +	struct dev_pm_opp *opp;
> +	unsigned long min_freq = 0;
> +
> +	opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &min_freq);

When min_freq is 0, dev_pm_opp_find_freq_ceil will return ERR_PTR(-EINVAL);

--- from drivers/base/power/opp/core.c ------ 
struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
                                             unsigned long *freq)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *opp;

        if (!dev || !freq) {
                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
                return ERR_PTR(-EINVAL);
        }
---------------------------------------------

Cheers,
MyungJoo