[PATCH 08/10] PM / Domains: Add support for removing PM domains

On 9 September 2016 at 17:17, Jon Hunter [off-list ref] wrote:

On 09/09/16 14:54, Jon Hunter wrote:

quoted

On 08/09/16 12:49, Ulf Hansson wrote:

quoted

On 16 August 2016 at 11:49, Jon Hunter [off-list ref] wrote:

quoted

The genpd framework allows users to add PM domains via the pm_genpd_init()
function, however, there is no corresponding function to remove a PM
domain. For most devices this may be fine as the PM domains are never
removed, however, for devices that wish to populate the PM domains from
within a driver, having the ability to remove a PM domain if the probing
of the device fails or the driver is unloaded is necessary.

Add the function pm_genpd_remove() to remove a PM domain by referencing
it's generic_pm_domain structure.

PM domains can only be removed if they are not a parent domain to
another PM domain and have no devices associated with them.

I think we should also check if the there's is a provider registered
for the genpd, as it should also prevent the genpd from being removed.
Right?

Yes I would agree. I had thought that after patch #4 of this series that
only the provider itself would be able to call this. However, we should
probably still verify that the provider has correctly remove itself.

So now I have the following. I am still not 100% happy. I cannot clear
the ->provider when calling of_genpd_del_provider() and so I cannot use
this to verify if the provider is present and so I need to check the
list of providers and it gets a bit messy. I have been wracking my
brains to find a better alternative (including a single function to
remove the provider and domains at once but there are issues with that
as well).

Instead of using the ->provider pointer to know whether the genpd has
a valid provider, why not just add an additional ->has_provider bool
flag in the genpd struct?

Simply set the flag when adding the provider and reset it when
removing it. Wouldn't that work?

I think that long term it may make sense to reference the providers
exclusively by the fwnode_handle and make the list of provider non-DT
specific. I could do it now, but it would increase the series.

Perhaps a good idea. Although I agree, let's not make that change as a
part of this series.

[...]

Kind regards
Uffe