PM: introduce set_target method in pm_ops

Commit 52ade9b3b97fd3bea42842a056fe0786c28d0555 changed the suspend code
ordering to execute pm_ops->prepare() after the device model per-device
.suspend() calls in order to fix some ACPI-related issues.  Unfortunately, it
broke the at91 platform which assumed that pm_ops->prepare() would be called
before suspending devices.

at91 used pm_ops->prepare() to get notified of the target system sleep state,
so that it could use this information while suspending devices.  However, with
the current suspend code ordering pm_ops->prepare() is called too late for
this purpose.  Thus, at91 needs an additional method in 'struct pm_ops' that
will be used for notifying the platform of the target system sleep state.
Moreover, in the future such a method will also be needed by ACPI.

This patch adds the .set_target() method to 'struct pm_ops' and makes the
suspend code call it, if implemented, before executing the device model
per-device .suspend() calls.  It also modifies the at91 code to use
pm_ops->set_target() instead of pm_ops->prepare().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 54 insertions, 18 deletions

diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 47ff676aca5f..ddf9184d561d 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -53,7 +53,7 @@ static suspend_state_t target_state;
 /*
  * Called after processes are frozen, but before we shutdown devices.
  */
-static int at91_pm_prepare(suspend_state_t state)
+static int at91_pm_set_target(suspend_state_t state)
 {
         target_state = state;
         return 0;
@@ -201,7 +201,7 @@ error:
 
 static struct pm_ops at91_pm_ops ={
         .valid          = at91_pm_valid_state,
-        .prepare        = at91_pm_prepare,
+        .set_target     = at91_pm_set_target,
         .enter          = at91_pm_enter,
 };
 
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 87545e0f0b58..b2c4fde4e994 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -110,37 +110,67 @@ typedef int __bitwise suspend_state_t;
 #define PM_SUSPEND_MAX          ((__force suspend_state_t) 4)
 
 /**
- * struct pm_ops - Callbacks for managing platform dependent suspend states.
- * @valid: Callback to determine whether the given state can be entered.
- *      Valid states are advertised in /sys/power/state but can still
- *      be rejected by prepare or enter if the conditions aren't right.
- *      There is a %pm_valid_only_mem function available that can be assigned
- *      to this if you only implement mem sleep.
+ * struct pm_ops - Callbacks for managing platform dependent system sleep
+ *      states.
  *
- * @prepare: Prepare the platform for the given suspend state. Can return a
- *      negative error code if necessary.
+ * @valid: Callback to determine if given system sleep state is supported by
+ *      the platform.
+ *      Valid (ie. supported) states are advertised in /sys/power/state.  Note
+ *      that it still may be impossible to enter given system sleep state if the
+ *      conditions aren't right.
+ *      There is the %pm_valid_only_mem function available that can be assigned
+ *      to this if the platform only supports mem sleep.
  *
- * @enter: Enter the given suspend state, must be assigned. Can return a
- *      negative error code if necessary.
+ * @set_target: Tell the platform which system sleep state is going to be
+ *      entered.
+ *      @set_target() is executed right prior to suspending devices.  The
+ *      information conveyed to the platform code by @set_target() should be
+ *      disregarded by the platform as soon as @finish() is executed and if
+ *      @prepare() fails.  If @set_target() fails (ie. returns nonzero),
+ *      @prepare(), @enter() and @finish() will not be called by the PM core.
+ *      This callback is optional.  However, if it is implemented, the argument
+ *      passed to @prepare(), @enter() and @finish() is meaningless and should
+ *      be ignored.
  *
- * @finish: Called when the system has left the given state and all devices
- *      are resumed. The return value is ignored.
+ * @prepare: Prepare the platform for entering the system sleep state indicated
+ *      by @set_target() or represented by the argument if @set_target() is not
+ *      implemented.
+ *      @prepare() is called right after devices have been suspended (ie. the
+ *      appropriate .suspend() method has been executed for each device) and
+ *      before the nonboot CPUs are disabled (it is executed with IRQs enabled).
+ *      This callback is optional.  It returns 0 on success or a negative
+ *      error code otherwise, in which case the system cannot enter the desired
+ *      sleep state (@enter() and @finish() will not be called in that case).
+ *
+ * @enter: Enter the system sleep state indicated by @set_target() or
+ *      represented by the argument if @set_target() is not implemented.
+ *      This callback is mandatory.  It returns 0 on success or a negative
+ *      error code otherwise, in which case the system cannot enter the desired
+ *      sleep state.
+ *
+ * @finish: Called when the system has just left a sleep state, right after
+ *      the nonboot CPUs have been enabled and before devices are resumed (it is
+ *      executed with IRQs enabled).  If @set_target() is not implemented, the
+ *      argument represents the sleep state being left.
+ *      This callback is optional, but should be implemented by the platforms
+ *      that implement @prepare().  If implemented, it is always called after
+ *      @enter() (even if @enter() fails).
  */
 struct pm_ops {
         int (*valid)(suspend_state_t state);
+        int (*set_target)(suspend_state_t state);
         int (*prepare)(suspend_state_t state);
         int (*enter)(suspend_state_t state);
         int (*finish)(suspend_state_t state);
 };
 
+extern struct pm_ops *pm_ops;
+
 /**
  * pm_set_ops - set platform dependent power management ops
  * @pm_ops: The new power management operations to set.
  */
 extern void pm_set_ops(struct pm_ops *pm_ops);
-extern struct pm_ops *pm_ops;
-extern int pm_suspend(suspend_state_t state);
-
 extern int pm_valid_only_mem(suspend_state_t state);
 
 /**
@@ -161,6 +191,8 @@ extern void arch_suspend_disable_irqs(void);
  */
 extern void arch_suspend_enable_irqs(void);
 
+extern int pm_suspend(suspend_state_t state);
+
 /*
  * Device power management
  */
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 8812985f3029..fc45ed22620f 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -15,7 +15,6 @@
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/init.h>
-#include <linux/pm.h>
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/resume-trace.h>
@@ -97,6 +96,11 @@ static int suspend_prepare(suspend_state_t state)
                 }
         }
 
+        if (pm_ops->set_target) {
+                error = pm_ops->set_target(state);
+                if (error)
+                        goto Thaw;
+        }
         suspend_console();
         error = device_suspend(PMSG_SUSPEND);
         if (error) {