[PATCH 10/11] PCI PM: Make pci_set_power_state() handle devices with no PM support

Rafael J. Wysocki
2009-03-14T11:33:55Z

From: Rafael J. Wysocki <rjw@sisk.pl>

There is a problem with PCI devices without any PM support (either
native or through the platform) that pci_set_power_state() always
returns error code for them, even if they are being put into D0.
However, such devices are always in D0, so pci_set_power_state()
should return success when attempting to put such a device into D0.
It also should update the current_state field for these devices as
appropriate. This modification is necessary so that the standard
configuration registers of these devices are successfully restored by
pci_restore_standard_config() during the "early" phase of resume.

In addition, pci_set_power_state() should check the value of
current_state before calling the platform to change the power state
of the device to avoid doing that unnecessarily.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/pci/pci.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

Index: linux-2.6/drivers/pci/pci.c
===================================================================
--- linux-2.6.orig/drivers/pci/pci.c
+++ linux-2.6/drivers/pci/pci.c
@@ -439,6 +439,10 @@ static int pci_raw_set_power_state(struc
u16 pmcsr;
bool need_restore = false;

+ /* Check if we're already there */
+ if (dev->current_state == state)
+ return 0;
+
if (!dev->pm_cap)
return -EIO;

@@ -449,10 +453,7 @@ static int pci_raw_set_power_state(struc
* Can enter D0 from any state, but if we can only go deeper
* to sleep if we're already in a low power state
*/
- if (dev->current_state == state) {
- /* we're already there */
- return 0;
- } else if (state != PCI_D0 && dev->current_state <= PCI_D3cold
+ if (state != PCI_D0 && dev->current_state <= PCI_D3cold
&& dev->current_state > state) {
dev_err(&dev->dev, "invalid power transition "
"(from state %d to %d)\n", dev->current_state, state);
@@ -570,12 +571,17 @@ int pci_set_power_state(struct pci_dev *
*/
return 0;

- if (state == PCI_D0 && platform_pci_power_manageable(dev)) {
+ /* Check if we're already there */
+ if (dev->current_state == state)
+ return 0;
+
+ if (state == PCI_D0) {
/*
* Allow the platform to change the state, for example via ACPI
* _PR0, _PS0 and some such, but do not trust it.
*/
- int ret = platform_pci_set_power_state(dev, PCI_D0);
+ int ret = platform_pci_power_manageable(dev) ?
+ platform_pci_set_power_state(dev, PCI_D0) : 0;
if (!ret)
pci_update_current_state(dev, PCI_D0);
}