[RFC PATCH 6/8] PM / Domains: Remove a provider by referencing the data pointer

[jonathanh@nvidia.com (Jon Hunter)]

On 05/08/16 12:55, Ulf Hansson wrote:
> On 21 June 2016 at 15:47, Jon Hunter <jonathanh@nvidia.com> wrote:
>>
>> On 15/06/16 15:38, Ulf Hansson wrote:
>>> On 4 March 2016 at 12:23, Jon Hunter <jonathanh@nvidia.com> wrote:
>>>> To remove a PM domain from the system, it is necessary to ensure
>>>> that any PM domain providers associated with the PM domain have
>>>> been removed. Otherwise it could be possible to obtain a pointer
>>>> to a PM domain structure that has been removed.
>>>>
>>>> PM domains now have a reference to the pointer for the PM domain
>>>> provider's data variable. Add a function so that a PM domain can
>>>> remove a PM domain provider by referencing the data pointer.
> 
> 
>>>>
>>>> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
>>>> ---
>>>>  drivers/base/power/domain.c | 24 ++++++++++++++++++++++++
>>>>  include/linux/pm_domain.h   |  2 ++
>>>>  2 files changed, 26 insertions(+)
>>>>
>>>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>>>> index 72055fef6256..438885f2455f 100644
>>>> --- a/drivers/base/power/domain.c
>>>> +++ b/drivers/base/power/domain.c
>>>> @@ -1738,6 +1738,30 @@ void of_genpd_del_provider(struct device_node *np)
>>>>  EXPORT_SYMBOL_GPL(of_genpd_del_provider);
>>>>
>>>>  /**
>>>> + * of_genpd_del_provider_by_data() - Remove a registered PM domain provider
>>>> + * @data: Pointer to the data associated with the PM domain provider
>>>> + *
>>>> + * Look up a PM domain provider based upon a pointer to it's data and
>>>> + * remove the PM domain provider from the list of providers.
>>>> + */
>>>> +void of_genpd_del_provider_by_data(void *data)
>>>> +{
>>>> +       struct of_genpd_provider *c, *cp;
>>>> +
>>>> +       mutex_lock(&of_genpd_mutex);
>>>> +       list_for_each_entry_safe(cp, c, &of_genpd_providers, link) {
>>>> +               if (cp->data == data) {
>>>> +                       list_del(&cp->link);
>>>> +                       of_node_put(cp->node);
>>>> +                       kfree(cp);
>>>> +                       break;
>>>> +               }
>>>> +       }
>>>> +       mutex_unlock(&of_genpd_mutex);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(of_genpd_del_provider_by_data);
>>>> +
>>>> +/**
>>>>   * of_genpd_get_from_provider() - Look-up PM domain
>>>>   * @genpdspec: OF phandle args to use for look-up
>>>>   *
>>>> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
>>>> index bed84413546f..7b7921a65cb0 100644
>>>> --- a/include/linux/pm_domain.h
>>>> +++ b/include/linux/pm_domain.h
>>>> @@ -199,6 +199,7 @@ int of_genpd_add_provider_simple(struct device_node *np,
>>>>  int of_genpd_add_provider_onecell(struct device_node *np,
>>>>                                   struct genpd_onecell_data *data);
>>>>  void of_genpd_del_provider(struct device_node *np);
>>>
>>> There's currently only one user of of_genpd_del_provider().
>>>
>>> Could this patch just convert that user to the new API, so we don't
>>> need to keep both the legacy and new one?
>>>
>>> I guess we could then just stick to the name "of_genpd_del_provider()".
>>
>> I had a look at this and to do that we would end up with
>> of_genpd_del_provider(struct device_node *np, void *data) where the user
>> should only pass one of the arguments. It seems a bit odd. However,
>> unless I have forgotten something, I wonder if we should just make
>> of_genpd_del_provider_by_name() a local function and not export this at
>> all? It seems more natural for users to delete a provider by the
>> device_node than by name rather than the data argument.
>>
>> The only problem I see with making of_genpd_del_provider_by_name() local
>> is that I need to add a prototype for the function at the top of the
>> domain.c source file so that it builds because __pm_genpd_remove() is
>> defined above it. Yes I could move __pm_genpd_remove() to the bottom of
>> the file but then it is not located next to pm_genpd_init() which seems odd.
>>
>> Let me know what you think.
> 
> Sorry for delay! I have now looked into this in more detail.

No problem. Thanks!

> When an genpd provider is added today, it's supposed to get a
> corresponding *unique* OF device node associated with it, right!?
> 
> If we store this OF device node from the provider in the struct
> generic_pm_domain, instead of the "provider_data pointer", we wouldn't
> need to the add of_genpd_del_provider_by_data() at all. Because we can
> use the currently available of_genpd_del_provider(), right!?
> 
> Or what am I missing? :-)

No that would work as well. I guess I was trying to make it non-DT
specific. However, for now it can be to simplify matters and it could
always be extended later if necessary.

I am also thinking about making pm_genpd_remove_tail()
of_genpd_remove_tail() as it seems silly to have both a struct device
pointer and a struct device_node pointer stored for the provider.

Cheers
Jon

-- 
nvpublic