[v3,4/5] PM / Domains: Add support for multi PM domains per device to genpd

To support devices being partitioned across multiple PM domains, let's
begin with extending genpd to cope with these kind of configurations.

Therefore, add a new exported function genpd_dev_pm_attach_by_id(), which
is similar to the existing genpd_dev_pm_attach(), but with the difference
that it allows its callers to provide an index to the PM domain that it
wants to attach.

Note that, genpd_dev_pm_attach_by_id() shall only be called by the driver
core / PM core, similar to how the existing dev_pm_domain_attach() makes
use of genpd_dev_pm_attach(). However, this is implemented by following
changes on top.

Because, only one PM domain can be attached per device, genpd needs to
create a virtual device that it can attach/detach instead. More precisely,
let the new function genpd_dev_pm_attach_by_id() register a virtual struct
device via calling device_register(). Then let it attach this device to the
corresponding PM domain, rather than the one that is provided by the
caller. The actual attaching is done via re-using the existing genpd OF
functions.

At successful attachment, genpd_dev_pm_attach_by_id() returns the created
virtual device, which allows the caller to operate on it to deal with power
management. Following changes on top, provides more details in this
regards.

To deal with detaching of a PM domain for the multiple PM domains case,
let's also extend the existing genpd_dev_pm_detach() function, to cover the
cleanup of the created virtual device, via make it call device_unregister()
on it. In this way, there is no need to introduce a new function to deal
with detach for the multiple PM domain case, but instead the existing one
is re-used.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/base/power/domain.c | 80 +++++++++++++++++++++++++++++++++++++
 include/linux/pm_domain.h   |  8 ++++
 2 files changed, 88 insertions(+)

Hi Ulf,

Am Donnerstag, den 31.05.2018, 12:59 +0200 schrieb Ulf Hansson:
> To support devices being partitioned across multiple PM domains, let's
> begin with extending genpd to cope with these kind of configurations.
> 
> Therefore, add a new exported function genpd_dev_pm_attach_by_id(), which
> is similar to the existing genpd_dev_pm_attach(), but with the difference
> that it allows its callers to provide an index to the PM domain that it
> wants to attach.
> 
> Note that, genpd_dev_pm_attach_by_id() shall only be called by the driver
> core / PM core, similar to how the existing dev_pm_domain_attach() makes
> use of genpd_dev_pm_attach(). However, this is implemented by following
> changes on top.

by_id() APIs are not really intuitive to use for driver writers. Other
subsystems have solved this by providing a "-names" property to give
the phandles a bit more meaning and then providing a by_name API. I
would really appreciate if PM domains could move in the same direction.

Regards,
Lucas

> Because, only one PM domain can be attached per device, genpd needs to
> create a virtual device that it can attach/detach instead. More precisely,
> let the new function genpd_dev_pm_attach_by_id() register a virtual struct
> device via calling device_register(). Then let it attach this device to the
> corresponding PM domain, rather than the one that is provided by the
> caller. The actual attaching is done via re-using the existing genpd OF
> functions.
> 
> At successful attachment, genpd_dev_pm_attach_by_id() returns the created
> virtual device, which allows the caller to operate on it to deal with power
> management. Following changes on top, provides more details in this
> regards.
> 
> To deal with detaching of a PM domain for the multiple PM domains case,
> let's also extend the existing genpd_dev_pm_detach() function, to cover the
> cleanup of the created virtual device, via make it call device_unregister()
> on it. In this way, there is no need to introduce a new function to deal
> with detach for the multiple PM domain case, but instead the existing one
> is re-used.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> Acked-by: Jon Hunter <jonathanh@nvidia.com>
> Tested-by: Jon Hunter <jonathanh@nvidia.com>
> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/base/power/domain.c | 80 +++++++++++++++++++++++++++++++++++++
>  include/linux/pm_domain.h   |  8 ++++
>  2 files changed, 88 insertions(+)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index b1fcbf917974..4925af5c4cf0 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2171,6 +2171,15 @@ struct generic_pm_domain *of_genpd_remove_last(struct device_node *np)
>  }
>  EXPORT_SYMBOL_GPL(of_genpd_remove_last);
>  
> +static void genpd_release_dev(struct device *dev)
> +{
> +	kfree(dev);
> +}
> +
> +static struct bus_type genpd_bus_type = {
> +	.name		= "genpd",
> +};
> +
>  /**
>   * genpd_dev_pm_detach - Detach a device from its PM domain.
>   * @dev: Device to detach.
> @@ -2208,6 +2217,10 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
>  
>  	/* Check if PM domain can be powered off after removing this device. */
>  	genpd_queue_power_off_work(pd);
> +
> +	/* Unregister the device if it was created by genpd. */
> +	if (dev->bus == &genpd_bus_type)
> +		device_unregister(dev);
>  }
>  
>  static void genpd_dev_pm_sync(struct device *dev)
> @@ -2298,6 +2311,67 @@ int genpd_dev_pm_attach(struct device *dev)
>  }
>  EXPORT_SYMBOL_GPL(genpd_dev_pm_attach);
>  
> +/**
> + * genpd_dev_pm_attach_by_id - Associate a device with one of its PM domains.
> + * @dev: The device used to lookup the PM domain.
> + * @index: The index of the PM domain.
> + *
> + * Parse device's OF node to find a PM domain specifier at the provided @index.
> + * If such is found, creates a virtual device and attaches it to the retrieved
> + * pm_domain ops. To deal with detaching of the virtual device, the ->detach()
> + * callback in the struct dev_pm_domain are assigned to genpd_dev_pm_detach().
> + *
> + * Returns the created virtual device if successfully attached PM domain, NULL
> + * when the device don't need a PM domain, else an ERR_PTR() in case of
> + * failures. If a power-domain exists for the device, but cannot be found or
> + * turned on, then ERR_PTR(-EPROBE_DEFER) is returned to ensure that the device
> + * is not probed and to re-try again later.
> + */
> +struct device *genpd_dev_pm_attach_by_id(struct device *dev,
> +					 unsigned int index)
> +{
> +	struct device *genpd_dev;
> +	int num_domains;
> +	int ret;
> +
> +	if (!dev->of_node)
> +		return NULL;
> +
> +	/* Deal only with devices using multiple PM domains. */
> +	num_domains = of_count_phandle_with_args(dev->of_node, "power-domains",
> +						 "#power-domain-cells");
> +	if (num_domains < 2 || index >= num_domains)
> +		return NULL;
> +
> +	/* Allocate and register device on the genpd bus. */
> +	genpd_dev = kzalloc(sizeof(*genpd_dev), GFP_KERNEL);
> +	if (!genpd_dev)
> +		return ERR_PTR(-ENOMEM);
> +
> +	dev_set_name(genpd_dev, "genpd:%u:%s", index, dev_name(dev));
> +	genpd_dev->bus = &genpd_bus_type;
> +	genpd_dev->release = genpd_release_dev;
> +
> +	ret = device_register(genpd_dev);
> +	if (ret) {
> +		kfree(genpd_dev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	/* Try to attach the device to the PM domain at the specified index. */
> +	ret = __genpd_dev_pm_attach(genpd_dev, dev->of_node, index);
> +	if (ret < 1) {
> +		device_unregister(genpd_dev);
> +		return ret ? ERR_PTR(ret) : NULL;
> +	}
> +
> +	pm_runtime_set_active(genpd_dev);
> +	pm_runtime_enable(genpd_dev);
> +
> +	return genpd_dev;
> +}
> +EXPORT_SYMBOL_GPL(genpd_dev_pm_attach_by_id);
> +
>  static const struct of_device_id idle_state_match[] = {
>  	{ .compatible = "domain-idle-state", },
>  	{ }
> @@ -2457,6 +2531,12 @@ unsigned int of_genpd_opp_to_performance_state(struct device *dev,
>  }
>  EXPORT_SYMBOL_GPL(of_genpd_opp_to_performance_state);
>  
> +static int __init genpd_bus_init(void)
> +{
> +	return bus_register(&genpd_bus_type);
> +}
> +core_initcall(genpd_bus_init);
> +
>  #endif /* CONFIG_PM_GENERIC_DOMAINS_OF */
>  
>  
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 42e0d649e653..82458e8e2e01 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -237,6 +237,8 @@ unsigned int of_genpd_opp_to_performance_state(struct device *dev,
>  				struct device_node *opp_node);
>  
>  int genpd_dev_pm_attach(struct device *dev);
> +struct device *genpd_dev_pm_attach_by_id(struct device *dev,
> +					 unsigned int index);
>  #else /* !CONFIG_PM_GENERIC_DOMAINS_OF */
>  static inline int of_genpd_add_provider_simple(struct device_node *np,
>  					struct generic_pm_domain *genpd)
> @@ -282,6 +284,12 @@ static inline int genpd_dev_pm_attach(struct device *dev)
>  	return 0;
>  }
>  
> +static inline struct device *genpd_dev_pm_attach_by_id(struct device *dev,
> +						       unsigned int index)
> +{
> +	return NULL;
> +}
> +
>  static inline
>  struct generic_pm_domain *of_genpd_remove_last(struct device_node *np)
>  {
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On 31/05/18 12:40, Lucas Stach wrote:
> Hi Ulf,
> 
> Am Donnerstag, den 31.05.2018, 12:59 +0200 schrieb Ulf Hansson:
>> To support devices being partitioned across multiple PM domains, let's
>> begin with extending genpd to cope with these kind of configurations.
>>
>> Therefore, add a new exported function genpd_dev_pm_attach_by_id(), which
>> is similar to the existing genpd_dev_pm_attach(), but with the difference
>> that it allows its callers to provide an index to the PM domain that it
>> wants to attach.
>>
>> Note that, genpd_dev_pm_attach_by_id() shall only be called by the driver
>> core / PM core, similar to how the existing dev_pm_domain_attach() makes
>> use of genpd_dev_pm_attach(). However, this is implemented by following
>> changes on top.
> 
> by_id() APIs are not really intuitive to use for driver writers. Other
> subsystems have solved this by providing a "-names" property to give
> the phandles a bit more meaning and then providing a by_name API. I
> would really appreciate if PM domains could move in the same direction.

As discussed here [0], there are plans to add that.

Cheers
Jon

[0] https://patchwork.ozlabs.org/patch/921938/