Re: [PATCH 1/3] pm/qos: allow state control of qos class

[Rafael J. Wysocki]

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....@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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