Hi,
Well, it looks like I should have reviewed this one more carefully.
On Thursday, August 11, 2011, jean.pihet@xxxxxxxxxxxxxx wrote:
> From: Jean Pihet <j-pihet@xxxxxx>
>
> Implement the per-device PM QoS constraints by creating a device
> PM QoS API, which calls the PM QoS constraints management core code.
>
> The per-device latency constraints data strctures are stored
> in the device dev_pm_info struct.
>
> The device PM code calls the init and destroy of the per-device constraints
> data struct in order to support the dynamic insertion and removal of the
> devices in the system.
>
> To minimize the data usage by the per-device constraints, the data struct
> is only allocated at the first call to dev_pm_qos_add_request.
> The data is later free'd when the device is removed from the system.
>
> Signed-off-by: Jean Pihet <j-pihet@xxxxxx>
> ---
> drivers/base/power/Makefile | 4 +-
> drivers/base/power/main.c | 3 +
> drivers/base/power/qos.c | 262 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/pm.h | 9 ++
> include/linux/pm_qos.h | 39 +++++++
> 5 files changed, 315 insertions(+), 2 deletions(-)
> create mode 100644 drivers/base/power/qos.c
>
> diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
> index 3647e11..1a61f89 100644
> --- a/drivers/base/power/Makefile
> +++ b/drivers/base/power/Makefile
> @@ -1,8 +1,8 @@
> -obj-$(CONFIG_PM) += sysfs.o generic_ops.o
> +obj-$(CONFIG_PM) += sysfs.o generic_ops.o qos.o
> obj-$(CONFIG_PM_SLEEP) += main.o wakeup.o
> obj-$(CONFIG_PM_RUNTIME) += runtime.o
> obj-$(CONFIG_PM_TRACE_RTC) += trace.o
> obj-$(CONFIG_PM_OPP) += opp.o
> obj-$(CONFIG_HAVE_CLK) += clock_ops.o
>
> -ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
> \ No newline at end of file
> +ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 06f09bf..f5c0e0e 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -22,6 +22,7 @@
> #include <linux/mutex.h>
> #include <linux/pm.h>
> #include <linux/pm_runtime.h>
> +#include <linux/pm_qos.h>
> #include <linux/resume-trace.h>
> #include <linux/interrupt.h>
> #include <linux/sched.h>
> @@ -97,6 +98,7 @@ void device_pm_add(struct device *dev)
> dev_name(dev->parent));
> list_add_tail(&dev->power.entry, &dpm_list);
> mutex_unlock(&dpm_list_mtx);
> + dev_pm_qos_constraints_init(dev);
> }
>
> /**
> @@ -107,6 +109,7 @@ void device_pm_remove(struct device *dev)
> {
> pr_debug("PM: Removing info for %s:%s\n",
> dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
> + dev_pm_qos_constraints_destroy(dev);
> complete_all(&dev->power.completion);
> mutex_lock(&dpm_list_mtx);
> list_del_init(&dev->power.entry);
> diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
> new file mode 100644
> index 0000000..465e419
> --- /dev/null
> +++ b/drivers/base/power/qos.c
> @@ -0,0 +1,262 @@
> +/*
> + * This module exposes the interface to kernel space for specifying
> + * per-device PM QoS dependencies. It provides infrastructure for registration
> + * of:
> + *
> + * Dependents on a QoS value : register requests
> + * Watchers of QoS value : get notified when target QoS value changes
> + *
> + * This QoS design is best effort based. Dependents register their QoS needs.
> + * Watchers register to keep track of the current QoS needs of the system.
> + *
> + * Note about the per-device constraint data struct allocation:
> + * . The per-device constraints data struct ptr is tored into the device
> + * dev_pm_info.
> + * . To minimize the data usage by the per-device constraints, the data struct
> + * is only allocated at the first call to dev_pm_qos_add_request.
> + * . The data is later free'd when the device is removed from the system.
> + * . The constraints_state variable from dev_pm_info tracks the data struct
> + * allocation state:
> + * DEV_PM_QOS_NO_DEVICE: No device present or device removed, no data
> + * allocated,
> + * DEV_PM_QOS_DEVICE_PRESENT: Device present, data not allocated and will be
> + * allocated at the first call to dev_pm_qos_add_request,
> + * DEV_PM_QOS_ALLOCATED: Device present, data allocated. The per-device
> + * PM QoS constraints framework is operational and constraints can be
> + * added, updated or removed using the dev_pm_qos_* API.
> + */
> +
> +/*#define DEBUG*/
Please remove this.
> +
> +#include <linux/pm_qos.h>
> +#include <linux/sched.h>
> +#include <linux/spinlock.h>
> +#include <linux/slab.h>
> +#include <linux/time.h>
> +#include <linux/fs.h>
> +#include <linux/device.h>
> +#include <linux/string.h>
> +#include <linux/platform_device.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
Are you sure all of the headers are necessary?
> +
> +
> +static void dev_pm_qos_constraints_allocate(struct device *dev);
> +
> +int dev_pm_qos_request_active(struct dev_pm_qos_request *req)
> +{
> + return req->dev != 0;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_request_active);
That should be a static inline in a header.
> +
> +/**
> + * dev_pm_qos_add_request - inserts new qos request into the list
> + * @req: pointer to a preallocated handle
> + * @dev: target device for the constraint
> + * @value: defines the qos request
> + *
> + * This function inserts a new entry in the device constraints list of
> + * requested qos performance characteristics. It recomputes the aggregate
> + * QoS expectations of parameters and initializes the dev_pm_qos_request
> + * handle. Caller needs to save this handle for later use in updates and
> + * removal.
> + */
> +void dev_pm_qos_add_request(struct dev_pm_qos_request *req, struct device *dev,
> + s32 value)
I'd use a different ordering of arguments, namely (dev, req, value).
> +{
> + if (!req) /*guard against callers passing in null */
> + return;
Why not to check for !dev too?
> +
> + if (dev_pm_qos_request_active(req)) {
> + WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already "
> + "added request\n");
> + return;
> + }
> + req->dev = dev;
> +
> + /* Allocate the constraints struct on the first call to add_request */
> + if (req->dev->power.constraints_state == DEV_PM_QOS_DEVICE_PRESENT)
> + dev_pm_qos_constraints_allocate(dev);
Why not to do
+ if (!req->dev->power.constraints)
+ dev_pm_qos_constraints_allocate(dev);
> +
> + /* Silently return if the device has been removed */
> + if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> + return;
> +
Hmm. What will happen if two callers run dev_pm_qos_add_request()
concurrently for the same device?
> + pm_qos_update_target(dev->power.constraints,
> + &req->node, PM_QOS_ADD_REQ, value);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
> +
> +/**
> + * dev_pm_qos_update_request - modifies an existing qos request
> + * @req : handle to list element holding a dev_pm_qos request to use
> + * @value: defines the qos request
> + *
> + * Updates an existing dev PM qos request along with updating the
> + * target value.
> + *
> + * Attempts are made to make this code callable on hot code paths.
> + */
> +void dev_pm_qos_update_request(struct dev_pm_qos_request *req,
> + s32 new_value)
> +{
> + if (!req) /*guard against callers passing in null */
> + return;
> +
> + if (!dev_pm_qos_request_active(req)) {
> + WARN(1, KERN_ERR "dev_pm_qos_update_request() called for "
> + "unknown object\n");
> + return;
> + }
> +
> + /* Silently return if the device has been removed */
> + if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> + return;
> +
> + if (new_value != req->node.prio)
> + pm_qos_update_target(
> + req->dev->power.constraints,
> + &req->node, PM_QOS_UPDATE_REQ, new_value);
I'm not sure what prevents dev_pm_qos_constraints_destroy() from removing
the list from under us while we're executing this?
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
> +
> +/**
> + * dev_pm_qos_remove_request - modifies an existing qos request
> + * @req: handle to request list element
> + *
> + * Will remove pm qos request from the list of constraints and
> + * recompute the current target value. Call this on slow code paths.
> + */
> +void dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
> +{
> + if (!req) /*guard against callers passing in null */
> + return;
> +
> + if (!dev_pm_qos_request_active(req)) {
> + WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for "
> + "unknown object\n");
> + return;
> + }
> +
> + /* Silently return if the device has been removed */
> + if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> + return;
> +
> + pm_qos_update_target(req->dev->power.constraints,
> + &req->node, PM_QOS_REMOVE_REQ,
> + PM_QOS_DEFAULT_VALUE);
Same here.
> + memset(req, 0, sizeof(*req));
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
> +
> +/**
> + * dev_pm_qos_add_notifier - sets notification entry for changes to target value
> + * of per-device PM QoS constraints
> + *
> + * @dev: target device for the constraint
> + * @notifier: notifier block managed by caller.
> + *
> + * Will register the notifier into a notification chain that gets called
> + * upon changes to the target value for the device.
> + */
> +int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
> +{
> + int retval = 0;
> +
> + /* Silently return if the device has been removed */
> + if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> + return retval;
> +
> + retval = blocking_notifier_chain_register(
> + dev->power.constraints->notifiers,
> + notifier);
That may be racing with dev_pm_qos_constraints_destroy() too.
> +
> + return retval;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
> +
> +/**
> + * dev_pm_qos_remove_notifier - deletes notification for changes to target value
> + * of per-device PM QoS constraints
> + *
> + * @dev: target device for the constraint
> + * @notifier: notifier block to be removed.
> + *
> + * Will remove the notifier from the notification chain that gets called
> + * upon changes to the target value.
> + */
> +int dev_pm_qos_remove_notifier(struct device *dev,
> + struct notifier_block *notifier)
> +{
> + int retval = 0;
> +
> + /* Silently return if the device has been removed */
> + if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> + return retval;
> +
> + retval = blocking_notifier_chain_unregister(
> + dev->power.constraints->notifiers,
> + notifier);
Same here.
> +
> + return retval;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
> +
> +/* Called at the first call to add_request, for constraint data allocation */
> +static void dev_pm_qos_constraints_allocate(struct device *dev)
> +{
> + struct pm_qos_constraints *c;
> + struct blocking_notifier_head *n;
> +
> + c = kzalloc(sizeof(*c), GFP_KERNEL);
> + if (!c)
> + return;
> +
> + n = kzalloc(sizeof(*n), GFP_KERNEL);
> + if (!n) {
> + kfree(c);
> + return;
> + }
> + BLOCKING_INIT_NOTIFIER_HEAD(n);
> +
> + dev->power.constraints = c;
> + plist_head_init(&dev->power.constraints->list, &dev->power.lock);
> + dev->power.constraints->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
> + dev->power.constraints->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
> + dev->power.constraints->type = PM_QOS_MIN;
> + dev->power.constraints->notifiers = n;
> + dev->power.constraints_state = DEV_PM_QOS_ALLOCATED;
> +}
> +
> +/* Called from the device PM subsystem at device insertion */
> +void dev_pm_qos_constraints_init(struct device *dev)
> +{
> + dev->power.constraints_state = DEV_PM_QOS_DEVICE_PRESENT;
Hmm. Is it insufficient to check if "constraints" is not NULL?
> +}
> +
> +/* Called from the device PM subsystem at device removal */
> +void dev_pm_qos_constraints_destroy(struct device *dev)
> +{
> + struct dev_pm_qos_request *req, *tmp;
> + enum dev_pm_qos_state constraints_state = dev->power.constraints_state;
> +
> + dev->power.constraints_state = DEV_PM_QOS_NO_DEVICE;
I'm not sure what the purpose of this is. I'd simply check if "constraints"
is not NULL and I'd flush the list if not.
Moreover, that has to go under a lock so that it doesn't race with
the other functions above. I think you can reuse power.lock for that.
> + if (constraints_state == DEV_PM_QOS_ALLOCATED) {
> + /* Flush the constraints list for the device */
> + plist_for_each_entry_safe(req, tmp,
> + &dev->power.constraints->list,
> + node)
> + /*
> + * Update constraints list and call the per-device
> + * callbacks if needed
> + */
> + pm_qos_update_target(req->dev->power.constraints,
> + &req->node, PM_QOS_REMOVE_REQ,
> + PM_QOS_DEFAULT_VALUE);
> +
> + kfree(dev->power.constraints->notifiers);
> + kfree(dev->power.constraints);
> + dev->power.constraints = NULL;
> + }
> +}
> +
Thanks,
Rafael
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