Re: [RFC PATCH 1/2] PM / domains: Introduce multi PM domains helpers

["Sridharan, Ranjani" <ranjani.sridharan@intel.com>]

On Mon, Mar 2, 2020 at 12:59 PM Daniel Baluta <daniel.baluta@oss.nxp.com>
wrote:

> From: Daniel Baluta <daniel.baluta@nxp.com>
>
> This patch introduces helpers support for multi PM domains.
>
> API consists of:
>
> 1) dev_multi_pm_attach - powers up all PM domains associated with a given
> device. Because we can attach one PM domain per device, we create
> virtual devices (children of initial device) and associate PM domains
> one per virtual device.
>
> 2) dev_multi_pm_detach - detaches all virtual devices from PM domains
> attached with.
>
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> ---
>  drivers/base/power/common.c | 93 +++++++++++++++++++++++++++++++++++++
>  include/linux/pm_domain.h   | 19 ++++++++
>  2 files changed, 112 insertions(+)
>
> diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
> index bbddb267c2e6..a90cc6b476e4 100644
> --- a/drivers/base/power/common.c
> +++ b/drivers/base/power/common.c
> @@ -228,3 +228,96 @@ void dev_pm_domain_set(struct device *dev, struct
> dev_pm_domain *pd)
>         device_pm_check_callbacks(dev);
>  }
>  EXPORT_SYMBOL_GPL(dev_pm_domain_set);
> +
> +/**
> + * dev_multi_pm_attach - power up device associated power domains
> + * @dev: The device used to lookup the PM domains
> + *
> + * Parse device's OF node to find all PM domains specifiers. For each
> power
> + * domain found, create a virtual device and associate it with the
> + * current power domain.
> + *
> + * This function should typically be invoked by a driver during the
> + * probe phase, in the case its device requires power management through
> + * multiple PM domains.
> + *
> + * Returns a pointer to @dev_multi_pm_domain_data if successfully
> attached PM
> + * domains, NULL if 0 or 1 PM domains specified, else an ERR_PTR() in
> case of
> + * failures.
> + */
> +struct dev_multi_pm_domain_data *dev_multi_pm_attach(struct device *dev)
> +{
> +       struct dev_multi_pm_domain_data *mpd, *retp;
> +       int num_domains;
> +       int i;
> +
> +       num_domains = of_count_phandle_with_args(dev->of_node,
> "power-domains",
> +                                                "#power-domain-cells");
> +       if (num_domains < 2)
>
Hi Daniel,

Just out of curiosity, should it be an error when num_domains is 1? Is it
an error because the expectation is that the caller would use
dev_pm_domain_attach() in that case?

+               return NULL;
> +
> +       mpd = devm_kzalloc(dev, GFP_KERNEL, sizeof(*mpd));
> +       if (!mpd)
> +               return ERR_PTR(-ENOMEM);
> +
> +       mpd->dev = dev;
> +       mpd->num_domains = num_domains;
> +
> +       mpd->virt_devs = devm_kmalloc_array(dev, mpd->num_domains,
> +                                           sizeof(*mpd->virt_devs),
> +                                           GFP_KERNEL);
> +       if (!mpd->virt_devs)
> +               return ERR_PTR(-ENOMEM);
> +
> +       mpd->links = devm_kmalloc_array(dev, mpd->num_domains,
> +                                       sizeof(*mpd->links), GFP_KERNEL);
> +       if (!mpd->links)
> +               return ERR_PTR(-ENOMEM);
> +
> +       for (i = 0; i < mpd->num_domains; i++) {
> +               mpd->virt_devs[i] = dev_pm_domain_attach_by_id(dev, i);
> +               if (IS_ERR(mpd->virt_devs[i])) {
> +                       retp = (struct dev_multi_pm_domain_data *)
> +                               mpd->virt_devs[i];
>
Should retp be PTR_ERR(mpd->virt_devs[i]) here?
Thanks,
Ranjani