[PATCH v1] PCI / PM: Really allow runtime PM without callback functions

Raag Jadav
2024-02-12T06:32:43Z

Commit c5eb1190074c ("PCI / PM: Allow runtime PM without callback
functions") tried to eliminate the need for runtime PM callbacks
by modifying pci_pm_runtime_suspend() and pci_pm_runtime_resume(),
but didn't modify pci_pm_runtime_idle() with relevant changes, which
still returns -ENOSYS if the driver supplies no runtime PM callbacks.

Fix this by modifying pci_pm_runtime_idle() such that it allows PCI
device power state transitions without runtime PM callbacks.

0) | pm_runtime_work() {
0) | rpm_idle() {
0) | rpm_check_suspend_allowed() {
0) 1.500 us | __dev_pm_qos_resume_latency(); /* = 0x7fffffff */
0) 4.840 us | } /* rpm_check_suspend_allowed = 0x0 */
0) 1.550 us | __rpm_get_callback(); /* = 0xffffffffb4bc84f0 */
0) 1.800 us | pci_pm_runtime_idle(); /* = -38 */
0) + 17.070 us | } /* rpm_idle = -38 */
0) + 22.450 us | } /* pm_runtime_work = -38 */

Debugged-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
---

This is not marked for linux-stable for the need of extensive testing
and can be backported after a few releases if no issues are reported.

drivers/pci/pci-driver.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 51ec9e7e784f..bb7f6775b350 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1382,10 +1382,7 @@ static int pci_pm_runtime_idle(struct device *dev)
if (!pci_dev->driver)
return 0;

- if (!pm)
- return -ENOSYS;
-
- if (pm->runtime_idle)
+ if (pm && pm->runtime_idle)
return pm->runtime_idle(dev);

return 0;
--
2.35.3