Re: [RFC][PATCH -mm 2/9] ACPI: Add acpi_pm_device_sleep_state helper routine

Rafael J. Wysocki
2007-07-03T13:58:49Z

On Monday, 2 July 2007 22:15, Rafael J. Wysocki wrote:
> On Monday, 2 July 2007 19:24, David Brownell wrote:
> > On Monday 02 July 2007, Rafael J. Wysocki wrote:
> > > On Monday, 2 July 2007 07:49, David Brownell wrote:
> >
> > > > Also, recall that this was originally PCI-specific. A generalized
> > > > approach would return a range of states, not a single state that
> > > > embeds a particular policy that may not be universally appropriate...
> > >
> > > Via pointers and the return value equal to 0 on success?
> >
> > It could as easily be one pointer: "int minmax[2]".
> > Then min == minmax[0] and max == minmax[1], and the
> > ACPI calls could write the caller's data directly.
> >
> > But in general, yes -- pointer, not single return value.
> >
> >
> > > > The logic was that PCI devices can all support PCI_D0 and PCI_D3.
> > > > For non-PCI devices we can't actually know that. So "min" should
> > > > probably default to ACPI_STATE_D0. If this returns a range, then
> > > > such issues can stay out of this code.
> > >
> > > The ACPI spec says that all devices must support D0 and D3.
> >
> > ISTR that it actually says they must "recognize" D3. That's
> > not the same as actually implementing a software controllable
> > power-off state ... and not the same as imposing a "use the
> > biggest numbered D-state" policy at this level.
>
> No, it literally says "All devices must support the D0 and D3 states" (that
> actually is stated in Appendix A, A.3.4 in the 3.0b specification).
>
> Still, I think that the question really is what we should return if _SxD or
> _SxW are not present.
>
> > > > > + /*
> > > > > + * If _PRW says we can wake from the upcoming system state, the _SxD
> > > > > + * value can wake ... and we'll assume a wakeup-aware driver. If _SxW
> > > > > + * methods exist (ACPI 3.x), they give the lowest power D-state that
> > > > > + * can also wake the system. _S0W can be valid.
> > > > > + */
> > > > > + if (acpi_target_sleep_state == ACPI_STATE_S0 ||
> > > > > + (dev->wakeup.state.enabled &&
>
> These things are the result of the evaluation of _PRW for that device and
> we need to check them here (or evaluate _PRW ourselves, but that wouldn't make
> sense, since it's already been evaulated), unless the caller tells us not to
> bother (we should provide the caller with a means to do it, though).

I looked at the ACPI spec again and updated the patch (please see below).

Greetings,
Rafael

---
From: Shaohua Li <shaohua.li@intel.com>, Rafael J. Wysocki <rjw@sisk.pl>

Based on the David Brownell's patch at
http://marc.info/?l=linux-acpi&m=117873972806360&w=2

Add a helper routine returning the lowest power (highest number) ACPI device
power state that given device can be in while the system is in the sleep state
indicated by acpi_target_sleep_state .

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/acpi/sleep/main.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++
include/acpi/acpi_bus.h | 2 +
2 files changed, 74 insertions(+)

Index: linux-2.6.22-rc7/drivers/acpi/sleep/main.c
===================================================================
--- linux-2.6.22-rc7.orig/drivers/acpi/sleep/main.c 2007-07-02 22:38:34.000000000 +0200
+++ linux-2.6.22-rc7/drivers/acpi/sleep/main.c 2007-07-03 11:57:27.000000000 +0200
@@ -269,6 +269,78 @@ static struct platform_hibernation_ops a
};
#endif /* CONFIG_SOFTWARE_SUSPEND */

+/**
+ * acpi_pm_device_sleep_state - return preferred power state of ACPI device
+ * in the system sleep state given by %acpi_target_sleep_state
+ * @dev: device to examine
+ * @wake: if set, the device should be able to wake up the system
+ * @d_min_p: used to store the upper limit of allowed states range
+ * Return value: preferred power state of the device on success, -ENODEV on
+ * failure (ie. if there's no 'struct acpi_device' for @dev)
+ *
+ * Find the lowest power (highest number) ACPI device power state that
+ * device @dev can be in while the system is in the sleep state represented
+ * by %acpi_target_sleep_state. If @wake is nonzero, the device should be
+ * able to wake up the system from this sleep state. If @d_min_p is set,
+ * the highest power (lowest number) device power state of @dev allowed
+ * in this system sleep state is stored at the location pointed to by it.
+ *
+ * The caller must ensure that @dev is valid before using this function.
+ */
+
+int acpi_pm_device_sleep_state(struct device *dev, int wake, int *d_min_p)
+{
+ acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
+ struct acpi_device *adev;
+ char acpi_method[] = "_SxD";
+ unsigned long d_min, d_max;
+
+ if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
+ printk(KERN_ERR "ACPI handle has no context!\n");
+ return -ENODEV;
+ }
+
+ acpi_method[2] = '0' + acpi_target_sleep_state;
+ /*
+ * If the sleep state is S0, we will return D3, but if the device has
+ * _S0W, we will use the value from _S0W
+ */
+ d_min = ACPI_STATE_D0;
+ d_max = ACPI_STATE_D3;
+
+ /*
+ * If present, _SxD methods return the minimum D-state (highest power
+ * state) we can use for the corresponding S-states. Otherwise, the
+ * minimum D-state is D0 (ACPI 3.x).
+ *
+ * NOTE: We rely on acpi_evaluate_integer() not clobbering the integer
+ * provided -- that's our fault recovery, we ignore retval.
+ */
+ if (acpi_target_sleep_state > ACPI_STATE_S0)
+ acpi_evaluate_integer(handle, acpi_method, NULL, &d_min);
+
+ /*
+ * If _PRW says we can wake up the system from the target sleep state,
+ * the D-state returned by _SxD is sufficient for that (we assume a
+ * wakeup-aware driver if wake is set). Still, if _SxW exists
+ * (ACPI 3.x), it should return the maximum (lowest power) D-state that
+ * can wake the system. _S0W may be valid, too.
+ */
+ if (acpi_target_sleep_state == ACPI_STATE_S0 ||
+ (wake && adev->wakeup.state.enabled &&
+ adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
+ acpi_method[3] = 'W';
+ acpi_evaluate_integer(handle, acpi_method, NULL, &d_max);
+ /* Sanity check */
+ if (d_max < d_min)
+ d_min = d_max;
+ }
+
+ if (d_min_p)
+ *d_min_p = d_min;
+ return d_max;
+}
+
/*
* Toshiba fails to preserve interrupts over S1, reinitialization
* of 8259 is needed after S1 resume.
Index: linux-2.6.22-rc7/include/acpi/acpi_bus.h
===================================================================
--- linux-2.6.22-rc7.orig/include/acpi/acpi_bus.h 2007-07-02 22:36:30.000000000 +0200
+++ linux-2.6.22-rc7/include/acpi/acpi_bus.h 2007-07-02 23:06:34.000000000 +0200
@@ -364,6 +364,8 @@ acpi_handle acpi_get_child(acpi_handle,
acpi_handle acpi_get_pci_rootbridge_handle(unsigned int, unsigned int);
#define DEVICE_ACPI_HANDLE(dev) ((acpi_handle)((dev)->archdata.acpi_handle))

+int acpi_pm_device_sleep_state(struct device *, int, int *);
+
#endif /* CONFIG_ACPI */

#endif /*__ACPI_BUS_H__*/