acpi_dev_pm_get_state() is used to determine the range of allowable
device power states when going into S3 suspend. This is implemented
by executing the _S3D and _S3W ACPI methods.
Linux follows the ACPI spec behaviour in that when _S3D is implemented
and _S3W is not, Linux will not go into a power state deeper than the one
returned by _S3D for a wakeup-enabled device.
However, this same logic is being applied to the case when neither
_S3D nor _S3W are present, and the result is that this function
decides that the device must stay in D0 (fully on) state.
This is breaking USB wakeups on Asus V222GA and Acer XC-830. _S3D and
_S3W are not present, so the USB controller is left in the D0 running
state during S3, and hence it is unable to generate a PME# wake event.
The ACPI spec is unclear on which power states are permissable for
wakeup-enabled devices when both _S3D and _S3W are missing.
However, USB wakeups work fine on these platforms under Windows, where
device manager shows that they are using D3 device state for the USB
controller in S3.
I assume that the "max = min" clamping done by the code here is
specifically written for the _S3D but no _S3W case. By making the
code true to those conditions, avoiding them on these platforms,
the controller will be put into D3 state and USB wakeups start working.
Additionally I feel that this change makes the code more directly
mirror the wording of the ACPI spec and it's associated lack of clarity.
Thanks to Mathias Nyman for pointing us in the right direction.
Signed-off-by: Daniel Drake <[email protected]>
Link: http://lkml.kernel.org/r/CAB4CAwf_k-WsF3zL4epm9TKAOu0h=Bv1XhXV_gY3bziOo_NPKA@mail.gmail.com
---
drivers/acpi/device_pm.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index c4d0a1c912f0..b945e37bcac0 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -543,6 +543,7 @@ static int acpi_dev_pm_get_state(struct device *dev, struct acpi_device *adev,
unsigned long long ret;
int d_min, d_max;
bool wakeup = false;
+ acpi_status sxd_status;
acpi_status status;
/*
@@ -565,8 +566,8 @@ static int acpi_dev_pm_get_state(struct device *dev, struct acpi_device *adev,
* provided if AE_NOT_FOUND is returned.
*/
ret = d_min;
- status = acpi_evaluate_integer(handle, method, NULL, &ret);
- if ((ACPI_FAILURE(status) && status != AE_NOT_FOUND)
+ sxd_status = acpi_evaluate_integer(handle, method, NULL, &ret);
+ if ((ACPI_FAILURE(sxd_status) && sxd_status != AE_NOT_FOUND)
|| ret > ACPI_STATE_D3_COLD)
return -ENODATA;
@@ -599,7 +600,11 @@ static int acpi_dev_pm_get_state(struct device *dev, struct acpi_device *adev,
method[3] = 'W';
status = acpi_evaluate_integer(handle, method, NULL, &ret);
if (status == AE_NOT_FOUND) {
- if (target_state > ACPI_STATE_S0)
+ /* No _SxW. In this case, the ACPI spec says that we
+ * must not go into any power state deeper than the
+ * value returned from _SxD.
+ */
+ if (sxd_status == AE_OK && target_state > ACPI_STATE_S0)
d_max = d_min;
} else if (ACPI_SUCCESS(status) && ret <= ACPI_STATE_D3_COLD) {
/* Fall back to D3cold if ret is not a valid state. */
--
2.14.1
Hi Daniel,
I love your patch! Perhaps something to improve:
[auto build test WARNING on v4.16-rc4]
[also build test WARNING on next-20180319]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Daniel-Drake/ACPI-PM-allow-deeper-wakeup-power-states-with-no-_SxD-nor-_SxW/20180319-185209
config: i386-randconfig-x074-201811 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
All warnings (new ones prefixed by >>):
drivers/acpi/device_pm.c: In function 'acpi_dev_pm_get_state':
>> drivers/acpi/device_pm.c:607:7: warning: 'sxd_status' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (sxd_status == AE_OK && target_state > ACPI_STATE_S0)
^
vim +/sxd_status +607 drivers/acpi/device_pm.c
516
517 /**
518 * acpi_dev_pm_get_state - Get preferred power state of ACPI device.
519 * @dev: Device whose preferred target power state to return.
520 * @adev: ACPI device node corresponding to @dev.
521 * @target_state: System state to match the resultant device state.
522 * @d_min_p: Location to store the highest power state available to the device.
523 * @d_max_p: Location to store the lowest power state available to the device.
524 *
525 * Find the lowest power (highest number) and highest power (lowest number) ACPI
526 * device power states that the device can be in while the system is in the
527 * state represented by @target_state. Store the integer numbers representing
528 * those stats in the memory locations pointed to by @d_max_p and @d_min_p,
529 * respectively.
530 *
531 * Callers must ensure that @dev and @adev are valid pointers and that @adev
532 * actually corresponds to @dev before using this function.
533 *
534 * Returns 0 on success or -ENODATA when one of the ACPI methods fails or
535 * returns a value that doesn't make sense. The memory locations pointed to by
536 * @d_max_p and @d_min_p are only modified on success.
537 */
538 static int acpi_dev_pm_get_state(struct device *dev, struct acpi_device *adev,
539 u32 target_state, int *d_min_p, int *d_max_p)
540 {
541 char method[] = { '_', 'S', '0' + target_state, 'D', '\0' };
542 acpi_handle handle = adev->handle;
543 unsigned long long ret;
544 int d_min, d_max;
545 bool wakeup = false;
546 acpi_status sxd_status;
547 acpi_status status;
548
549 /*
550 * If the system state is S0, the lowest power state the device can be
551 * in is D3cold, unless the device has _S0W and is supposed to signal
552 * wakeup, in which case the return value of _S0W has to be used as the
553 * lowest power state available to the device.
554 */
555 d_min = ACPI_STATE_D0;
556 d_max = ACPI_STATE_D3_COLD;
557
558 /*
559 * If present, _SxD methods return the minimum D-state (highest power
560 * state) we can use for the corresponding S-states. Otherwise, the
561 * minimum D-state is D0 (ACPI 3.x).
562 */
563 if (target_state > ACPI_STATE_S0) {
564 /*
565 * We rely on acpi_evaluate_integer() not clobbering the integer
566 * provided if AE_NOT_FOUND is returned.
567 */
568 ret = d_min;
569 sxd_status = acpi_evaluate_integer(handle, method, NULL, &ret);
570 if ((ACPI_FAILURE(sxd_status) && sxd_status != AE_NOT_FOUND)
571 || ret > ACPI_STATE_D3_COLD)
572 return -ENODATA;
573
574 /*
575 * We need to handle legacy systems where D3hot and D3cold are
576 * the same and 3 is returned in both cases, so fall back to
577 * D3cold if D3hot is not a valid state.
578 */
579 if (!adev->power.states[ret].flags.valid) {
580 if (ret == ACPI_STATE_D3_HOT)
581 ret = ACPI_STATE_D3_COLD;
582 else
583 return -ENODATA;
584 }
585 d_min = ret;
586 wakeup = device_may_wakeup(dev) && adev->wakeup.flags.valid
587 && adev->wakeup.sleep_state >= target_state;
588 } else {
589 wakeup = adev->wakeup.flags.valid;
590 }
591
592 /*
593 * If _PRW says we can wake up the system from the target sleep state,
594 * the D-state returned by _SxD is sufficient for that (we assume a
595 * wakeup-aware driver if wake is set). Still, if _SxW exists
596 * (ACPI 3.x), it should return the maximum (lowest power) D-state that
597 * can wake the system. _S0W may be valid, too.
598 */
599 if (wakeup) {
600 method[3] = 'W';
601 status = acpi_evaluate_integer(handle, method, NULL, &ret);
602 if (status == AE_NOT_FOUND) {
603 /* No _SxW. In this case, the ACPI spec says that we
604 * must not go into any power state deeper than the
605 * value returned from _SxD.
606 */
> 607 if (sxd_status == AE_OK && target_state > ACPI_STATE_S0)
608 d_max = d_min;
609 } else if (ACPI_SUCCESS(status) && ret <= ACPI_STATE_D3_COLD) {
610 /* Fall back to D3cold if ret is not a valid state. */
611 if (!adev->power.states[ret].flags.valid)
612 ret = ACPI_STATE_D3_COLD;
613
614 d_max = ret > d_min ? ret : d_min;
615 } else {
616 return -ENODATA;
617 }
618 }
619
620 if (d_min_p)
621 *d_min_p = d_min;
622
623 if (d_max_p)
624 *d_max_p = d_max;
625
626 return 0;
627 }
628
---
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