Subject: [PATCH RFC v3 1/2] PM / Domains: Extend API pm_genpd_dev_need_restore to use restore types

From: [email-masked] (Marek Szyprowski)
Date: Tue, 16 Dec 2014 12:10:57 +0100

Hello,

On 2014-12-13 17:51, Amit Daniel Kachhap wrote:
> Instead of using bool to restore suspended devices initially, use flags
> like GPD_DEV_SUSPEND_INIT, GPD_DEV_RESTORE_INIT and GPD_DEV_RESTORE_FORCE.
> The first two flags will be similar to the existing true/false functionality.
> The third flag may be used to force restore of suspended devices
> whenever their associated power domain is turned on.
>
> Currently, PD power off function powers off all the associated unused
> devices. The functionality added in this patch is similar to it.
>
> This feature may be used for those devices which are always in ON state
> if the PD associated with them is ON but may need local runtime resume
> and suspend during PD On/Off. These devices (like clock) may not implement
> complete pm_runtime calls such as pm_runtime_get/pm_runtime_put due to
> subsystems interaction behaviour or any other reason.
>
> The model works like,
>      DEV1 (Attaches itself with PD but no calls to pm_runtime_get and
>      /	pm_runtime_put. Its local runtime_suspend/resume is invoked via
>     /	GPD_DEV_RESTORE_FORCE option)
>    /
> PD -- DEV2 (Implements complete PM runtime and calls pm_runtime_get and
>    \	pm_runtime_put. This in turn invokes PD On/Off)
>     \
>      DEV3 (Similar to DEV1)
>
> Signed-off-by: Amit Daniel Kachhap <[email-masked]>

The idea of adding new gen_pd flag and reusing runtime pm calls intead 
of additional
notifiers looks promising, but I have some doubts. I don't see any 
guarantee that
devices with GPD_DEV_RESTORE_FORCE flag will be suspended after all 
"normal" devices
and restored before them. Without such assumption it will be hard to use 
this approach
for iommu related activities, because device might need to use (in its 
suspend/resume
callbacks) the functionality provided by the other device with 
GPD_DEV_RESTORE_FORCE
flag. Maybe some additional flags like suspend/resume priority (or more 
flags) will
solve somehow this dependency.

> ---
> This work is continuation of earlier work,
>
> In V2: Completely removed notfiers and add support for huge clock list to be
> 	suspended and restored. There was some issue in this as some clocks are
> 	not exposed and are just initialised by bootloaders. This approach
> 	required all of them to be exposed which is cumbersome. Also some
> 	clock API's set_parent are disabling the original parent clocks
> 	which is not required.
> 	Link (https://lkml.org/lkml/2014/11/24/290)
>
> In V1: Implemented PM Domain notfier such as PD_ON_PRE, PD_ON_POST
> 	PD_OFF_PRE and PD_OFF_POST. This was not supported and other
> 	options suggested. link (http://www.spinics.net/lists/linux-samsung-soc/msg38442.html)
>
> This work may also assist exynos iommu pm runtime posted earlier by Marek
> http://lists.linaro.org/pipermail/linaro-mm-sig/2014-August/004099.html
> 	
>   drivers/base/power/domain.c | 40 ++++++++++++++++++++++++++++++++++++----
>   include/linux/pm_domain.h   | 15 +++++++++++++--
>   2 files changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 6a103a3..d955a05 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -49,6 +49,7 @@
>   
>   static LIST_HEAD(gpd_list);
>   static DEFINE_MUTEX(gpd_list_lock);
> +static void __pm_genpd_restore_devices(struct generic_pm_domain *genpd);
>   
>   static struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
>   {
> @@ -176,6 +177,8 @@ static int genpd_power_on(struct generic_pm_domain *genpd)
>   	pr_warn("%s: Power-%s latency exceeded, new value %lld ns\n",
>   		genpd->name, "on", elapsed_ns);
>   
> +	__pm_genpd_restore_devices(genpd);
> +
>   	return ret;
>   }
>   
> @@ -453,6 +456,24 @@ static void __pm_genpd_restore_device(struct pm_domain_data *pdd,
>   }
>   
>   /**
> + * __pm_genpd_restore_devices- Restore the pre-suspend state of all device
> + *				according to the restore flag.
> + * @genpd: PM domain the device belongs to.
> + */
> +static void __pm_genpd_restore_devices(struct generic_pm_domain *genpd)
> +{
> +	struct pm_domain_data *pdd;
> +	struct generic_pm_domain_data *gpd_data;
> +
> +	/* Force restore the devices according to the restore flag */
> +	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
> +		gpd_data = to_gpd_data(pdd);
> +		if (gpd_data->force_restore == true)
> +			__pm_genpd_restore_device(pdd, genpd);
> +	}
> +}
> +
> +/**
>    * genpd_abort_poweroff - Check if a PM domain power off should be aborted.
>    * @genpd: PM domain to check.
>    *
> @@ -1469,6 +1490,7 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>   	gpd_data->base.dev = dev;
>   	list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
>   	gpd_data->need_restore = -1;
> +	gpd_data->force_restore = false;
>   	gpd_data->td.constraint_changed = true;
>   	gpd_data->td.effective_constraint_ns = -1;
>   	mutex_unlock(&gpd_data->lock);
> @@ -1561,18 +1583,28 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
>   /**
>    * pm_genpd_dev_need_restore - Set/unset the device's "need restore" flag.
>    * @dev: Device to set/unset the flag for.
> - * @val: The new value of the device's "need restore" flag.
> + * @val: This can have values GPD_DEV_SUSPEND_INIT or GPD_DEV_RESTORE_INIT
> + *	together with GPD_DEV_RESTORE_FORCE.
>    */
> -void pm_genpd_dev_need_restore(struct device *dev, bool val)
> +void pm_genpd_dev_need_restore(struct device *dev, unsigned int val)
>   {
>   	struct pm_subsys_data *psd;
> +	struct generic_pm_domain_data *pdd;
>   	unsigned long flags;
>   
>   	spin_lock_irqsave(&dev->power.lock, flags);
>   
>   	psd = dev_to_psd(dev);
> -	if (psd && psd->domain_data)
> -		to_gpd_data(psd->domain_data)->need_restore = val ? 1 : 0;
> +	if (psd && psd->domain_data) {
> +		pdd = to_gpd_data(psd->domain_data);
> +		if (val & GPD_DEV_SUSPEND_INIT)
> +			pdd->need_restore = 0;
> +		else if (val & GPD_DEV_RESTORE_INIT)
> +			pdd->need_restore = 1;
> +
> +		if (val & GPD_DEV_RESTORE_FORCE)
> +			pdd->force_restore = true;
> +	}
>   
>   	spin_unlock_irqrestore(&dev->power.lock, flags);
>   }
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 6cd20d5..8aa74ee 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -20,6 +20,15 @@
>   /* Defines used for the flags field in the struct generic_pm_domain */
>   #define GENPD_FLAG_PM_CLK	(1U << 0) /* PM domain uses PM clk */
>   
> +/* Defines used for the types of restore */
> +#define	GPD_DEV_SUSPEND_INIT	0x1	/* Initiate the device runtime as
> +					   suspend/resume/suspend... */
> +#define	GPD_DEV_RESTORE_INIT	0x10	/* Initiate the device runtime as
> +					   resume/suspend/suspend... */
> +#define	GPD_DEV_RESTORE_FORCE	0x100	/* Force these devices to always do
> +					   resume in PD power on. Initial
> +					   behaviour can be one of the above */
> +
>   enum gpd_status {
>   	GPD_STATE_ACTIVE = 0,	/* PM domain is active */
>   	GPD_STATE_WAIT_MASTER,	/* PM domain's master is being waited for */
> @@ -116,6 +125,7 @@ struct generic_pm_domain_data {
>   	struct mutex lock;
>   	unsigned int refcount;
>   	int need_restore;
> +	bool force_restore;
>   };
>   
>   #ifdef CONFIG_PM_GENERIC_DOMAINS
> @@ -140,7 +150,7 @@ extern int __pm_genpd_name_add_device(const char *domain_name,
>   
>   extern int pm_genpd_remove_device(struct generic_pm_domain *genpd,
>   				  struct device *dev);
> -extern void pm_genpd_dev_need_restore(struct device *dev, bool val);
> +extern void pm_genpd_dev_need_restore(struct device *dev, unsigned int val);
>   extern int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
>   				  struct generic_pm_domain *new_subdomain);
>   extern int pm_genpd_add_subdomain_names(const char *master_name,
> @@ -187,7 +197,8 @@ static inline int pm_genpd_remove_device(struct generic_pm_domain *genpd,
>   {
>   	return -ENOSYS;
>   }
> -static inline void pm_genpd_dev_need_restore(struct device *dev, bool val) {}
> +static inline void pm_genpd_dev_need_restore(struct device *dev,
> +						unsigned int val) {}
>   static inline int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
>   					 struct generic_pm_domain *new_sd)
>   {

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland