[PATCH v2 1/5] PM: domains: Add helper functions to attach/detach multiple PM domains

Ulf Hansson
2024-01-05T16:01:13Z

Attaching/detaching of a device to multiple PM domains has started to
become a common operation for many drivers, typically during ->probe() and
->remove(). In most cases, this has lead to lots of boilerplate code in the
drivers.

To fixup up the situation, let's introduce a pair of helper functions,
dev_pm_domain_attach|detach_list(), that driver can use instead of the
open-coding. Note that, it seems reasonable to limit the support for these
helpers to DT based platforms, at it's the only valid use case for now.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

Changes in v2:
- Fix NULL pointer bug pointed out by Nikunj.

---
drivers/base/power/common.c | 134 ++++++++++++++++++++++++++++++++++++
include/linux/pm_domain.h | 38 ++++++++++
2 files changed, 172 insertions(+)

diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
index 44ec20918a4d..327d168dd37a 100644
--- a/drivers/base/power/common.c
+++ b/drivers/base/power/common.c
@@ -167,6 +167,115 @@ struct device *dev_pm_domain_attach_by_name(struct device *dev,
}
EXPORT_SYMBOL_GPL(dev_pm_domain_attach_by_name);

+/**
+ * dev_pm_domain_attach_list - Associate a device with its PM domains.
+ * @dev: The device used to lookup the PM domains for.
+ * @data: The data used for attaching to the PM domains.
+ * @list: An out-parameter with an allocated list of attached PM domains.
+ *
+ * This function helps to attach a device to its multiple PM domains. The
+ * caller, which is typically a driver's probe function, may provide a list of
+ * names for the PM domains that we should try to attach the device to, but it
+ * may also provide an empty list, in case the attach should be done for all of
+ * the available PM domains.
+ *
+ * Callers must ensure proper synchronization of this function with power
+ * management callbacks.
+ *
+ * Returns the number of attached PM domains or a negative error code in case of
+ * a failure. Note that, to detach the list of PM domains, the driver shall call
+ * dev_pm_domain_detach_list(), typically during the remove phase.
+ */
+int dev_pm_domain_attach_list(struct device *dev,
+ const struct dev_pm_domain_attach_data *data,
+ struct dev_pm_domain_list **list)
+{
+ struct device_node *np = dev->of_node;
+ struct dev_pm_domain_list *pds;
+ struct device *pd_dev = NULL;
+ int ret, i, num_pds = 0;
+ bool by_id = true;
+ u32 pd_flags = data ? data->pd_flags : 0;
+ u32 link_flags = pd_flags & PD_FLAG_NO_DEV_LINK ? 0 :
+ DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME;
+
+ if (dev->pm_domain)
+ return -EEXIST;
+
+ /* For now this is limited to OF based platforms. */
+ if (!np)
+ return 0;
+
+ if (data && data->pd_names) {
+ num_pds = data->num_pd_names;
+ by_id = false;
+ } else {
+ num_pds = of_count_phandle_with_args(np, "power-domains",
+ "#power-domain-cells");
+ }
+
+ if (num_pds <= 0)
+ return 0;
+
+ pds = devm_kzalloc(dev, sizeof(*pds), GFP_KERNEL);
+ if (!pds)
+ return -ENOMEM;
+
+ pds->pd_devs = devm_kcalloc(dev, num_pds, sizeof(*pds->pd_devs),
+ GFP_KERNEL);
+ if (!pds->pd_devs)
+ return -ENOMEM;
+
+ pds->pd_links = devm_kcalloc(dev, num_pds, sizeof(*pds->pd_links),
+ GFP_KERNEL);
+ if (!pds->pd_links)
+ return -ENOMEM;
+
+ if (link_flags && pd_flags & PD_FLAG_DEV_LINK_ON)
+ link_flags |= DL_FLAG_RPM_ACTIVE;
+
+ for (i = 0; i < num_pds; i++) {
+ if (by_id)
+ pd_dev = dev_pm_domain_attach_by_id(dev, i);
+ else
+ pd_dev = dev_pm_domain_attach_by_name(dev,
+ data->pd_names[i]);
+ if (IS_ERR_OR_NULL(pd_dev)) {
+ ret = pd_dev ? PTR_ERR(pd_dev) : -ENODEV;
+ goto err_attach;
+ }
+
+ if (link_flags) {
+ struct device_link *link;
+
+ link = device_link_add(dev, pd_dev, link_flags);
+ if (!link) {
+ ret = -ENODEV;
+ goto err_link;
+ }
+
+ pds->pd_links[i] = link;
+ }
+
+ pds->pd_devs[i] = pd_dev;
+ }
+
+ pds->num_pds = num_pds;
+ *list = pds;
+ return num_pds;
+
+err_link:
+ dev_pm_domain_detach(pd_dev, true);
+err_attach:
+ while (--i >= 0) {
+ if (pds->pd_links[i])
+ device_link_del(pds->pd_links[i]);
+ dev_pm_domain_detach(pds->pd_devs[i], true);
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_attach_list);
+
/**
* dev_pm_domain_detach - Detach a device from its PM domain.
* @dev: Device to detach.
@@ -187,6 +296,31 @@ void dev_pm_domain_detach(struct device *dev, bool power_off)
}
EXPORT_SYMBOL_GPL(dev_pm_domain_detach);

+/**
+ * dev_pm_domain_detach_list - Detach a list of PM domains.
+ * @list: The list of PM domains to detach.
+ *
+ * This function reverse the actions from dev_pm_domain_attach_list().
+ * Typically it should be invoked during the remove phase from drivers.
+ *
+ * Callers must ensure proper synchronization of this function with power
+ * management callbacks.
+ */
+void dev_pm_domain_detach_list(struct dev_pm_domain_list *list)
+{
+ int i;
+
+ if (!list)
+ return;
+
+ for (i = 0; i < list->num_pds; i++) {
+ if (list->pd_links[i])
+ device_link_del(list->pd_links[i]);
+ dev_pm_domain_detach(list->pd_devs[i], true);
+ }
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_detach_list);
+
/**
* dev_pm_domain_start - Start the device through its PM domain.
* @dev: Device to start.
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 34663d0d5c55..6b71fb69c349 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -19,6 +19,33 @@
#include <linux/cpumask.h>
#include <linux/time64.h>

+/*
+ * Flags to control the behaviour when attaching a device to its PM domains.
+ *
+ * PD_FLAG_NO_DEV_LINK: As the default behaviour creates a device-link
+ * for every PM domain that gets attached, this
+ * flag can be used to skip that.
+ *
+ * PD_FLAG_DEV_LINK_ON: Add the DL_FLAG_RPM_ACTIVE to power-on the
+ * supplier and its PM domain when creating the
+ * device-links.
+ *
+ */
+#define PD_FLAG_NO_DEV_LINK BIT(0)
+#define PD_FLAG_DEV_LINK_ON BIT(1)
+
+struct dev_pm_domain_attach_data {
+ const char * const *pd_names;
+ const u32 num_pd_names;
+ const u32 pd_flags;
+};
+
+struct dev_pm_domain_list {
+ struct device **pd_devs;
+ struct device_link **pd_links;
+ u32 num_pds;
+};
+
/*
* Flags to control the behaviour of a genpd.
*
@@ -432,7 +459,11 @@ struct device *dev_pm_domain_attach_by_id(struct device *dev,
unsigned int index);
struct device *dev_pm_domain_attach_by_name(struct device *dev,
const char *name);
+int dev_pm_domain_attach_list(struct device *dev,
+ const struct dev_pm_domain_attach_data *data,
+ struct dev_pm_domain_list **list);
void dev_pm_domain_detach(struct device *dev, bool power_off);
+void dev_pm_domain_detach_list(struct dev_pm_domain_list *list);
int dev_pm_domain_start(struct device *dev);
void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd);
int dev_pm_domain_set_performance_state(struct device *dev, unsigned int state);
@@ -451,7 +482,14 @@ static inline struct device *dev_pm_domain_attach_by_name(struct device *dev,
{
return NULL;
}
+static inline int dev_pm_domain_attach_list(struct device *dev,
+ const struct dev_pm_domain_attach_data *data,
+ struct dev_pm_domain_list **list)
+{
+ return 0;
+}
static inline void dev_pm_domain_detach(struct device *dev, bool power_off) {}
+static inline void dev_pm_domain_detach_list(struct dev_pm_domain_list *list) {}
static inline int dev_pm_domain_start(struct device *dev)
{
return 0;
--
2.34.1