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

From: [email-masked] (Lina Iyer)
Date: Mon, 10 Oct 2016 09:03:01 -0600

On Mon, Oct 10 2016 at 04:01 -0600, Ulf Hansson wrote:
>On 8 October 2016 at 00:36, Lina Iyer <[email-masked]> 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 <[email-masked]>
>> Signed-off-by: Ulf Hansson <[email-masked]>
>> Signed-off-by: Lina Iyer <[email-masked]>
>> ---
>>  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().
>
Hmm.. I thought about it. There are 2 return values from this function.
If we return a pointer to the allocated memory, we still have to return
the size of it as an argument. I wasn't happy splitting the return
values in 2 different places.

>> +{
>> +       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?
>
OK
>> +
>> +       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.
>
Hmm.. Didn't realize that.. will fix.

>> +               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.
>
Hmm.. OK

Thanks,
Lina
>> +
>>  #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