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SubjectRe: [PATCH 1/3] pm/qos: allow state control of qos class
On 11/27/2013 12:20 AM, Jacob Pan wrote:
> When power capping or thermal control is needed, CPU QOS latency cannot
> be satisfied. This patch adds a state variable to indicate whether a QOS
> class (including all constraint requests) should be ignored.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>

Honestly, I don't like this. I know the motivation and what you're
trying to achieve, but I don't like the approach.

I need to think a bit more about that.

Thanks,
Rafael


> ---
> include/linux/pm_qos.h | 10 +++++++++-
> kernel/power/qos.c | 24 ++++++++++++++++++++++++
> 2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
> index 5a95013..648b50b 100644
> --- a/include/linux/pm_qos.h
> +++ b/include/linux/pm_qos.h
> @@ -10,7 +10,7 @@
> #include <linux/device.h>
> #include <linux/workqueue.h>
>
> -enum {
> +enum pm_qos_class {
> PM_QOS_RESERVED = 0,
> PM_QOS_CPU_DMA_LATENCY,
> PM_QOS_NETWORK_LATENCY,
> @@ -20,6 +20,11 @@ enum {
> PM_QOS_NUM_CLASSES,
> };
>
> +enum pm_qos_state {
> + PM_QOS_CONSTRAINT_AVAILABLE,
> + PM_QOS_CONSTRAINT_IGNORED,
> +};
> +
> enum pm_qos_flags_status {
> PM_QOS_FLAGS_UNDEFINED = -1,
> PM_QOS_FLAGS_NONE,
> @@ -77,6 +82,7 @@ struct pm_qos_constraints {
> struct plist_head list;
> s32 target_value; /* Do not change to 64 bit */
> s32 default_value;
> + enum pm_qos_state state;
> enum pm_qos_type type;
> struct blocking_notifier_head *notifiers;
> };
> @@ -123,6 +129,8 @@ int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier);
> int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier);
> int pm_qos_request_active(struct pm_qos_request *req);
> s32 pm_qos_read_value(struct pm_qos_constraints *c);
> +void pm_qos_set_constraint_class_state(enum pm_qos_class class,
> + enum pm_qos_state state);
>
> #ifdef CONFIG_PM
> enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev, s32 mask);
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index 8dff9b4..cf475b0 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -146,6 +146,11 @@ static inline int pm_qos_get_value(struct pm_qos_constraints *c)
>
> s32 pm_qos_read_value(struct pm_qos_constraints *c)
> {
> + /* return invalid default value if constraints cannot be met, e.g.
> + * during idle injection.
> + */
> + if (c->state == PM_QOS_CONSTRAINT_IGNORED)
> + return PM_QOS_DEFAULT_VALUE;
> return c->target_value;
> }
>
> @@ -353,6 +358,25 @@ void pm_qos_add_request(struct pm_qos_request *req,
> }
> EXPORT_SYMBOL_GPL(pm_qos_add_request);
>
> +void pm_qos_set_constraint_class_state(enum pm_qos_class class,
> + enum pm_qos_state state)
> +{
> + struct pm_qos_constraints *c = pm_qos_array[class]->constraints;
> + unsigned long curr_value;
> +
> + if (c->state == state)
> + return;
> + curr_value = (state == PM_QOS_CONSTRAINT_IGNORED) ?
> + PM_QOS_DEFAULT_VALUE : c->target_value;
> + c->state = state;
> +
> + /* notify existing QOS requests change */
> + blocking_notifier_call_chain(c->notifiers,
> + curr_value,
> + NULL);
> +}
> +EXPORT_SYMBOL_GPL(pm_qos_set_constraint_class_state);
> +
> /**
> * pm_qos_update_request - modifies an existing qos request
> * @req : handle to list element holding a pm_qos request to use



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