Re: [PATCH v1 2/3] OPP: Add function to look up required OPP's for a given OPP

[Chanwoo Choi <cwchoi00@gmail.com>]

Hi,

Absolutely, I like this approach. I think that it is necessary to make
the connection
between frequencies of devices. But, I have a question on below.

2019년 6월 22일 (토) 오전 9:35, Saravana Kannan <saravanak@google.com>님이 작성:
>
> Add a function that allows looking up required OPPs given a source OPP
> table, destination OPP table and the source OPP.
>
> Signed-off-by: Saravana Kannan <saravanak@google.com>
> ---
>  drivers/opp/core.c     | 54 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm_opp.h | 11 +++++++++
>  2 files changed, 65 insertions(+)
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 74c7bdc6f463..4f7870bffbf8 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1830,6 +1830,60 @@ void dev_pm_opp_put_genpd_virt_dev(struct opp_table *opp_table,
>                 dev_err(virt_dev, "Failed to find required device entry\n");
>  }
>
> +/**
> + * dev_pm_opp_xlate_opp() - Find required OPP for src_table OPP.
> + * @src_table: OPP table which has dst_table as one of its required OPP table.
> + * @dst_table: Required OPP table of the src_table.
> + * @pstate: OPP of the src_table.
> + *
> + * This function returns the OPP (present in @dst_table) pointed out by the
> + * "required-opps" property of the OPP (present in @src_table).
> + *
> + * The callers are required to call dev_pm_opp_put() for the returned OPP after
> + * use.
> + *
> + * Return: destination table OPP on success, otherwise NULL on errors.
> + */
> +struct dev_pm_opp *dev_pm_opp_xlate_opp(struct opp_table *src_table,
> +                                       struct opp_table *dst_table,
> +                                       struct dev_pm_opp *src_opp)
> +{
> +       struct dev_pm_opp *opp, *dest_opp = NULL;
> +       int i;
> +
> +       if (!src_table || !dst_table || !src_opp)
> +               return NULL;
> +
> +       for (i = 0; i < src_table->required_opp_count; i++) {
> +               if (src_table->required_opp_tables[i]->np == dst_table->np)
> +                       break;
> +       }
> +
> +       if (unlikely(i == src_table->required_opp_count)) {
> +               pr_err("%s: Couldn't find matching OPP table (%p: %p)\n",
> +                      __func__, src_table, dst_table);
> +               return NULL;
> +       }
> +
> +       mutex_lock(&src_table->lock);
> +
> +       list_for_each_entry(opp, &src_table->opp_list, node) {
> +               if (opp == src_opp) {
> +                       dest_opp = opp->required_opps[i];

Correct me if I am wrong. This patch assume that 'i' index is same on between
[1] and [2]. But in order to guarantee this assumption, all OPP entries
in the same opp_table have to have the same number of 'required-opps' properties
and keep the sequence among 'required-opps' entries.

[1] src_table->required_opp_tables[i]->np
[2] opp->required_opps[I];

For example, three OPP entries in the 'parent_bus_opp'
have the different sequence of 'required-opps' and the different
number of 'required-opps'. Is it no problem?

parent_bus_opp: opp_table {
    compatible = "operating-points-v2";

    opp2 {
        opp-hz = /bits/ 64 <200000>;
        required-opps = <&child_bus_a_opp2>, <&child_bus_b_opp2>,
<&child_bus_c_opp2>;
    };

    opp1 {
        opp-hz = /bits/ 64 <200000>;
        // change the sequence between child_bus_b_opp2  and child_bus_c_opp2
        required-opps = <&child_bus_a_opp2>, <&child_bus_c_opp2>,
<&child_bus_b_opp2>
    };

    opp0 {
        opp-hz = /bits/ 64 <200000>;
        // missing 'child_bus_a_opp2'
        required-opps = <&child_bus_c_opp2>, <&child_bus_b_opp2>
    };

}



> +                       dev_pm_opp_get(dest_opp);
> +                       goto unlock;
> +               }
> +       }
> +
> +       pr_err("%s: Couldn't find matching OPP (%p: %p)\n", __func__, src_table,
> +              dst_table);
> +
> +unlock:
> +       mutex_unlock(&src_table->lock);
> +
> +       return dest_opp;
> +}
> +
>  /**
>   * dev_pm_opp_xlate_performance_state() - Find required OPP's pstate for src_table.
>   * @src_table: OPP table which has dst_table as one of its required OPP table.
> diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> index b150fe97ce5a..bc5c68bdfc8d 100644
> --- a/include/linux/pm_opp.h
> +++ b/include/linux/pm_opp.h
> @@ -134,6 +134,9 @@ void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table);
>  struct opp_table *dev_pm_opp_set_genpd_virt_dev(struct device *dev, struct device *virt_dev, int index);
>  void dev_pm_opp_put_genpd_virt_dev(struct opp_table *opp_table, struct device *virt_dev);
>  int dev_pm_opp_xlate_performance_state(struct opp_table *src_table, struct opp_table *dst_table, unsigned int pstate);
> +struct dev_pm_opp *dev_pm_opp_xlate_opp(struct opp_table *src_table,
> +                                       struct opp_table *dst_table,
> +                                       struct dev_pm_opp *src_opp);
>  int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
>  int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
>  int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask);
> @@ -307,6 +310,14 @@ static inline int dev_pm_opp_xlate_performance_state(struct opp_table *src_table
>         return -ENOTSUPP;
>  }
>
> +static inline struct dev_pm_opp *dev_pm_opp_xlate_opp(
> +                                               struct opp_table *src_table,
> +                                               struct opp_table *dst_table,
> +                                               struct dev_pm_opp *src_opp)
> +{
> +       return NULL;
> +}
> +
>  static inline int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
>  {
>         return -ENOTSUPP;
> --
> 2.22.0.410.gd8fdbe21b5-goog
>


-- 
Best Regards,
Chanwoo Choi