On 2017-10-24 at 13:35:05 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
>
[cut]
> @@ -63,10 +60,14 @@ static bool default_suspend_ok(struct de
>
> spin_unlock_irqrestore(&dev->power.lock, flags);
>
> - if (constraint_ns < 0)
> + if (constraint_ns == 0)
> return false;
>
> - constraint_ns *= NSEC_PER_USEC;
> + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> + constraint_ns = -1;
> + else
> + constraint_ns *= NSEC_PER_USEC;
> +
> /*
> * We can walk the children without any additional locking, because
> * they all have been suspended at this point and their
> @@ -76,14 +77,19 @@ static bool default_suspend_ok(struct de
> device_for_each_child(dev, &constraint_ns,
> dev_update_qos_constraint);
>
> - if (constraint_ns > 0) {
> - constraint_ns -= td->suspend_latency_ns +
> - td->resume_latency_ns;
> - if (constraint_ns == 0)
> - return false;
> + if (constraint_ns < 0) {
> + /* The children have no constraints. */
> + td->effective_constraint_ns =
> PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
> + td->cached_suspend_ok = true;
> + } else {
> + constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns;
> + if (constraint_ns > 0) {
> + td->effective_constraint_ns = constraint_ns;
> + td->cached_suspend_ok = true;
> + } else {
> + td->effective_constraint_ns = 0;
If the resume latency constraint was increased after this,
default_power_down_ok may not consider the new value. default_suspend_ok needs
to get called first if the new value is to be read.
This is because dev_pm_qos_read_value will get called only if
effective_constraint_ns has a negative value. default_suspend_ok initializes
effective_constraint_ns with -1 before doing the calculations.
default_power_down_ok does not initialize it to -1 and uses
the existing value.
A comment in default_power_down_ok implies it is not necessary to call
default_suspend_ok before calling default_power_down_ok. In that case,
default_power_down_ok should be able to get the new latency constraint value.
> + }
> }
> - td->effective_constraint_ns = constraint_ns;
> - td->cached_suspend_ok = constraint_ns >= 0;
>
> /*
> * The children have been suspended already, so we don't need to take
> @@ -145,13 +151,14 @@ static bool __default_power_down_ok(stru
> td = &to_gpd_data(pdd)->td;
> constraint_ns = td->effective_constraint_ns;
> /* default_suspend_ok() need not be called before us. */
> - if (constraint_ns < 0) {
> + if (constraint_ns < 0)
> constraint_ns = dev_pm_qos_read_value(pdd->dev);
> - constraint_ns *= NSEC_PER_USEC;
> - }
> - if (constraint_ns == 0)
> +
> + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> continue;
>
> + constraint_ns *= NSEC_PER_USEC;
> +
> /*
> * constraint_ns cannot be negative here, because the device has
> * been suspended.
