linux-kernel - Re: [PATCH v1 3/3] PM / devfreq: Add required OPPs support to passive governor

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Message-ID: <CAGTfZH1COWzhDBr63S18md44ypKixstHHsX7cm5LnAhXXbfecA@mail.gmail.com>
Date:   Sat, 22 Jun 2019 21:00:59 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, kernel-team@...roid.com,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/3] PM / devfreq: Add required OPPs support to passive governor

Hi,

Absolutely, I agree this approach.
But, I add some comments on below. please check them.

2019년 6월 22일 (토) 오전 9:36, Saravana Kannan <saravanak@...gle.com>님이 작성:
>
> Look at the required OPPs of the "parent" device to determine the OPP that
> is required from the slave device managed by the passive governor. This
> allows having mappings between a parent device and a slave device even when
> they don't have the same number of OPPs.
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/devfreq/governor_passive.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 3bc29acbd54e..bd4a98bb15b1 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -21,8 +21,9 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>         struct devfreq_passive_data *p_data
>                         = (struct devfreq_passive_data *)devfreq->data;
>         struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
> +       struct opp_table *opp_table = NULL, *c_opp_table = NULL;

In this function, the base device is passive devfreq device.
So, I think that better to define the 'parent_opp_table' instead of 'opp_table'
indicating the OPP table of parent devfreq device. And better to define
just 'opp_table' instead of 'c_opp_table' indicating the passive devfreq device.
- opp_table -> parent_opp_table
- c_opp_table -> opp_table

>         unsigned long child_freq = ULONG_MAX;
> -       struct dev_pm_opp *opp;
> +       struct dev_pm_opp *opp = NULL, *c_opp = NULL;

Ditto. I think that better to define the variables as following:
- opp -> parent_opp
- c_cpp -> opp

>         int i, count, ret = 0;
>
>         /*
> @@ -65,7 +66,20 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>                 goto out;
>         }
>
> -       dev_pm_opp_put(opp);
> +       opp_table = dev_pm_opp_get_opp_table(parent_devfreq->dev.parent);

devfreq_passive_get_target_freq() is called frequently for DVFS support.
I think that you have to add 'struct opp_table *opp_table' instance to
'struct devfreq'
and then get 'opp_table' instance in the devfreq_add_device().

devfreq_add_device() already get the OPP information by using
dev_pm_opp_get_suspend_opp_freq().
You can add following code nearby dev_pm_opp_get_suspend_opp_freq() in
devfreq_add_device().
- devfreq->opp_table = dev_pm_opp_get_opp_table(dev);


> +       if (IS_ERR_OR_NULL(opp_table)) {
> +               ret = PTR_ERR(opp_table);
> +               goto out;
> +       }
> +
> +       c_opp_table = dev_pm_opp_get_opp_table(devfreq->dev.parent);
> +       if (!IS_ERR_OR_NULL(c_opp_table))
> +               c_opp = dev_pm_opp_xlate_opp(opp_table, c_opp_table, opp);
> +       if (c_opp) {
> +               *freq = dev_pm_opp_get_freq(c_opp);
> +               dev_pm_opp_put(c_opp);
> +               goto out;
> +       }
>
>         /*
>          * Get the OPP table's index of decided freqeuncy by governor
> @@ -92,6 +106,13 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>         *freq = child_freq;
>
>  out:
> +       if (!IS_ERR_OR_NULL(opp_table))
> +               dev_pm_opp_put_opp_table(opp_table);
> +       if (!IS_ERR_OR_NULL(c_opp_table))
> +               dev_pm_opp_put_opp_table(c_opp_table);
> +       if (!IS_ERR_OR_NULL(opp))
> +               dev_pm_opp_put(opp);
> +
>         return ret;
>  }
>
> --
> 2.22.0.410.gd8fdbe21b5-goog
>


-- 
Best Regards,
Chanwoo Choi