On 28 January 2016 at 17:33, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> The genpd framework allows users to add power-domains via the
> pm_genpd_init() function, however, there is no corresponding function
> to remove a power-domain. For most devices this may be fine as the power
> domains are never removed, however, for devices that wish to populate
> the power-domains from within a driver, having the ability to remove a
> power domain if the probing of the device fails or the driver is unloaded
> is necessary. Therefore, add a function to remove a power-domain. Please
> note that the power domain can only be removed if there are no devices
> using the power-domain and it is not linked to another domain.
>
> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> ---
> drivers/base/power/domain.c | 26 ++++++++++++++++++++++++++
> include/linux/pm_domain.h | 5 +++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 45e3641b427d..b4120121bcac 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -1529,6 +1529,32 @@ void pm_genpd_init(struct generic_pm_domain *genpd,
> }
> EXPORT_SYMBOL_GPL(pm_genpd_init);
>
> +/**
> + * pm_genpd_remove - Remove a generic I/O PM domain object.
> + * @genpd: PM domain object to remove.
> + */
> +int pm_genpd_remove(struct generic_pm_domain *genpd)
> +{
> + if (IS_ERR_OR_NULL(genpd))
> + return -EINVAL;
> +
> + mutex_lock(&genpd->lock);
pm_genpd_summary_show() first locks the gpd_list_lock, then the genpd lock.
Please preserve that order here as well, to prevent potential deadlocks.
> +
> + if (!list_empty(&genpd->master_links)
> + || !list_empty(&genpd->slave_links) || genpd->device_count) {
> + mutex_unlock(&genpd->lock);
> + return -EBUSY;
> + }
> +
> + mutex_lock_nested(&gpd_list_lock, SINGLE_DEPTH_NESTING);
Why the nesting, can this really cause lockdep warnings?
> + list_del(&genpd->gpd_list_node);
> + mutex_unlock(&gpd_list_lock);
> + mutex_unlock(&genpd->lock);
Before returning, you need to make sure there isn't a scheduled work
for powering off the genpd.
That might happen for example happen via genpd_poweroff_unused().
Otherwise, the caller of pm_genpd_remove() might free the memory while
the genpd struct is still in use...
I assume a cancel_delayed_work_sync() should do the trick here.
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pm_genpd_remove);
> +
> #ifdef CONFIG_PM_GENERIC_DOMAINS_OF
> /*
> * Device Tree based PM domain providers.
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index db21d3995f7e..0d661998fa74 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -123,6 +123,7 @@ extern int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
> struct generic_pm_domain *target);
> extern void pm_genpd_init(struct generic_pm_domain *genpd,
> struct dev_power_governor *gov, bool is_off);
> +extern int pm_genpd_remove(struct generic_pm_domain *genpd);
>
> extern struct dev_power_governor simple_qos_governor;
> extern struct dev_power_governor pm_domain_always_on_gov;
> @@ -161,6 +162,10 @@ static inline void pm_genpd_init(struct generic_pm_domain *genpd,
> struct dev_power_governor *gov, bool is_off)
> {
> }
> +static inline int pm_genpd_remove(struct generic_pm_domain *genpd)
> +{
> + return -ENOTSUPP;
> +}
> #endif
>
> static inline int pm_genpd_add_device(struct generic_pm_domain *genpd,
> --
> 2.1.4
>
Kind regards
Uffe
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