On Wed, Nov 01, 2023 at 11:04:07AM +0200, Abel Vesa wrote:
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>
> Some power-domains may be capable of relying on the HW to control the power
> for a device that's hooked up to it. Typically, for these kinds of
> configurations the device doesn't really need to be attached to a PM domain
> (genpd), from Linux point of view.
Per patch 5, this description isn't correct.
Linux enables the power-domain, which in turn enables parent domains
etc. Once the firmware is booted the hardware-control mechanism is
engaged, but until then, and in order to keep the supplies to the domain
voted for, Linux needs a proper genpd.
Regards,
Bjorn
> However, in some cases the behaviour of
> the power-domain and its device can be changed in runtime.
>
> To allow a consumer driver to change the behaviour of the PM domain for its
> device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
> let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
> which the genpd provider should implement if it can support switching
> between HW controlled mode and SW controlled mode. Similarly, add the
> dev_pm_genpd_get_hwmode() to allow consumers to read the current mode and
> its corresponding optional genpd callback, ->get_hwmode_dev(), which the
> genpd provider can also implement for reading back the mode from the
> hardware.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
> ---
> drivers/base/power/domain.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pm_domain.h | 17 +++++++++++
> 2 files changed, 86 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index da1777e39eaa..3fb1a234c7f2 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -550,6 +550,75 @@ void dev_pm_genpd_synced_poweroff(struct device *dev)
> }
> EXPORT_SYMBOL_GPL(dev_pm_genpd_synced_poweroff);
>
> +/**
> + * dev_pm_genpd_set_hwmode - Set the HW mode for the device and its PM domain.
> + *
> + * @dev: Device for which the HW-mode should be changed.
> + * @enable: Value to set or unset the HW-mode.
> + *
> + * Some PM domains can rely on HW signals to control the power for a device. To
> + * allow a consumer driver to switch the behaviour for its device in runtime,
> + * which may be beneficial from a latency or energy point of view, this function
> + * may be called.
> + *
> + * It is assumed that the users guarantee that the genpd wouldn't be detached
> + * while this routine is getting called.
> + *
> + * Returns 0 on success and negative error values on failures.
> + */
> +int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
> +{
> + struct generic_pm_domain *genpd;
> + int ret = 0;
> +
> + genpd = dev_to_genpd_safe(dev);
> + if (!genpd)
> + return -ENODEV;
> +
> + if (!genpd->set_hwmode_dev)
> + return -EOPNOTSUPP;
> +
> + genpd_lock(genpd);
> +
> + if (dev_gpd_data(dev)->hw_mode == enable)
> + goto out;
> +
> + ret = genpd->set_hwmode_dev(genpd, dev, enable);
> + if (!ret)
> + dev_gpd_data(dev)->hw_mode = enable;
> +
> +out:
> + genpd_unlock(genpd);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_genpd_set_hwmode);
> +
> +/**
> + * dev_pm_genpd_get_hwmode - Get the HW mode setting for the device.
> + *
> + * @dev: Device for which the current HW-mode setting should be fetched.
> + *
> + * This helper function allows consumer drivers to fetch the current HW mode
> + * setting of its the device.
> + *
> + * It is assumed that the users guarantee that the genpd wouldn't be detached
> + * while this routine is getting called.
> + */
> +bool dev_pm_genpd_get_hwmode(struct device *dev)
> +{
> + struct generic_pm_domain *genpd;
> +
> + genpd = dev_to_genpd_safe(dev);
> + if (!genpd)
> + return false;
> +
> + if (genpd->get_hwmode_dev)
> + return genpd->get_hwmode_dev(genpd, dev);
> +
> + return dev_gpd_data(dev)->hw_mode;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);
> +
> static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
> {
> unsigned int state_idx = genpd->state_idx;
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 34663d0d5c55..0e7d177fdc3e 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -151,6 +151,10 @@ struct generic_pm_domain {
> int (*set_performance_state)(struct generic_pm_domain *genpd,
> unsigned int state);
> struct gpd_dev_ops dev_ops;
> + int (*set_hwmode_dev)(struct generic_pm_domain *domain,
> + struct device *dev, bool enable);
> + bool (*get_hwmode_dev)(struct generic_pm_domain *domain,
> + struct device *dev);
> int (*attach_dev)(struct generic_pm_domain *domain,
> struct device *dev);
> void (*detach_dev)(struct generic_pm_domain *domain,
> @@ -213,6 +217,7 @@ struct generic_pm_domain_data {
> unsigned int performance_state;
> unsigned int default_pstate;
> unsigned int rpm_pstate;
> + bool hw_mode;
> void *data;
> };
>
> @@ -242,6 +247,8 @@ int dev_pm_genpd_remove_notifier(struct device *dev);
> void dev_pm_genpd_set_next_wakeup(struct device *dev, ktime_t next);
> ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
> void dev_pm_genpd_synced_poweroff(struct device *dev);
> +int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
> +bool dev_pm_genpd_get_hwmode(struct device *dev);
>
> extern struct dev_power_governor simple_qos_governor;
> extern struct dev_power_governor pm_domain_always_on_gov;
> @@ -310,6 +317,16 @@ static inline ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev)
> static inline void dev_pm_genpd_synced_poweroff(struct device *dev)
> { }
>
> +static inline int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline bool dev_pm_genpd_get_hwmode(struct device *dev)
> +{
> + return false;
> +}
> +
> #define simple_qos_governor (*(struct dev_power_governor *)(NULL))
> #define pm_domain_always_on_gov (*(struct dev_power_governor *)(NULL))
> #endif
>
> --
> 2.34.1
>
