Re: [PATCH v2 3/8] PM / Domains: Allow domain power states to be read from DT

[Ulf Hansson <ulf.hansson@linaro.org>]

On 8 October 2016 at 00:36, Lina Iyer <lina.iyer@linaro.org> wrote:
> This patch allows domains to define idle states in the DT. SoC's can
> define domain idle states in DT using the "domain-idle-states" property
> of the domain provider. Add API to read the idle states from DT that can
> be set in the genpd object.
>
> This patch is based on the original patch by Marc Titinger.
>
> Signed-off-by: Marc Titinger <mtitinger+renesas@baylibre.com>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
> ---
>  drivers/base/power/domain.c | 95 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm_domain.h   |  8 ++++
>  2 files changed, 103 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 4e87170..4208b67 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -1917,6 +1917,101 @@ out:
>         return ret ? -EPROBE_DEFER : 0;
>  }
>  EXPORT_SYMBOL_GPL(genpd_dev_pm_attach);
> +
> +static const struct of_device_id idle_state_match[] = {
> +       { .compatible = "arm,idle-state", },
> +       { }
> +};
> +
> +static int genpd_parse_state(struct genpd_power_state *genpd_state,
> +                                   struct device_node *state_node)
> +{
> +       int err;
> +       u32 residency;
> +       u32 entry_latency, exit_latency;
> +       const struct of_device_id *match_id;
> +
> +       match_id = of_match_node(idle_state_match, state_node);
> +       if (!match_id)
> +               return -EINVAL;
> +
> +       err = of_property_read_u32(state_node, "entry-latency-us",
> +                                               &entry_latency);
> +       if (err) {
> +               pr_debug(" * %s missing entry-latency-us property\n",
> +                                               state_node->full_name);
> +               return -EINVAL;
> +       }
> +
> +       err = of_property_read_u32(state_node, "exit-latency-us",
> +                                               &exit_latency);
> +       if (err) {
> +               pr_debug(" * %s missing exit-latency-us property\n",
> +                                               state_node->full_name);
> +               return -EINVAL;
> +       }
> +
> +       err = of_property_read_u32(state_node, "min-residency-us", &residency);
> +       if (!err)
> +               genpd_state->residency_ns = 1000 * residency;
> +
> +       genpd_state->power_on_latency_ns = 1000 * exit_latency;
> +       genpd_state->power_off_latency_ns = 1000 * entry_latency;
> +
> +       return 0;
> +}
> +
> +/**
> + * of_genpd_parse_idle_states: Return array of idle states for the genpd.
> + *
> + * @dn: The genpd device node
> + * @states: The pointer to which the state array will be saved.
> + * @n: The count of elements in the array returned from this function.
> + *
> + * Returns the device states parsed from the OF node. The memory for the states
> + * is allocated by this function and is the responsibility of the caller to
> + * free the memory after use.
> + */
> +int of_genpd_parse_idle_states(struct device_node *dn,
> +                       struct genpd_power_state **states, int *n)

Instead of taking **states as a parameter, let's instead return it as
a pointer for the allocated struct. In case of failures, let's return
ERR_PTR().

> +{
> +       struct genpd_power_state *st;
> +       struct device_node *np;
> +       int i = 0;
> +       int err, ret;
> +       int count;
> +       struct of_phandle_iterator it;
> +
> +       count = of_count_phandle_with_args(dn, "domain-idle-states", NULL);

If count is zero or an error, we should return an error code (ERR_PTR()). Right?

> +
> +       st = kcalloc(count, sizeof(*st), GFP_KERNEL);
> +       if (!st)
> +               return -ENOMEM;
> +
> +       /* Loop over the phandles until all the requested entry is found */
> +       of_for_each_phandle(&it, err, dn, "domain-idle-states", NULL, 0) {
> +               np = of_node_get(it.node);

I don't think you need to increment the usage count for the device
node as that is already managed by of_for_each_phandle().

It's only in the error case below, when it's needed.

> +               ret = genpd_parse_state(&st[i++], np);
> +               if (ret) {
> +                       pr_err
> +                       ("Parsing idle state node %s failed with err %d\n",
> +                                                       np->full_name, ret);
> +                       of_node_put(np);
> +                       goto fail;

The goto seems unnecessary. Why not deal with all error handling here
and return the error code?

> +               }
> +               of_node_put(np);

According the comment above, you should be able to remove this.

> +       }
> +
> +       *n = count;
> +       *states = st;
> +
> +       return 0;
> +fail:
> +       kfree(st);
> +       return ret;
> +}
> +EXPORT_SYMBOL(of_genpd_parse_idle_states);

Please use EXPORT_SYMBOL_GPL() instead.

> +
>  #endif /* CONFIG_PM_GENERIC_DOMAINS_OF */
>
>
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index f4492eb..b489496 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -205,6 +205,8 @@ extern int of_genpd_add_device(struct of_phandle_args *args,
>  extern int of_genpd_add_subdomain(struct of_phandle_args *parent,
>                                   struct of_phandle_args *new_subdomain);
>  extern struct generic_pm_domain *of_genpd_remove_last(struct device_node *np);
> +extern int of_genpd_parse_idle_states(struct device_node *dn,
> +                       struct genpd_power_state **states, int *n);
>
>  int genpd_dev_pm_attach(struct device *dev);
>  #else /* !CONFIG_PM_GENERIC_DOMAINS_OF */
> @@ -234,6 +236,12 @@ static inline int of_genpd_add_subdomain(struct of_phandle_args *parent,
>         return -ENODEV;
>  }
>
> +static inline int of_genpd_parse_idle_states(struct device_node *dn,
> +                       struct genpd_power_state **states, int *n)
> +{
> +       return -ENODEV;
> +}
> +
>  static inline int genpd_dev_pm_attach(struct device *dev)
>  {
>         return -ENODEV;
> --
> 2.7.4
>

Kind regards
Uffe