[PATCH 1/2] PM: sleep: Do not mark devices without PM callbacks active on resume

[Abel Vesa]

Devices without system sleep callbacks get power.smart_suspend set in
device_prepare_smart_suspend(), unless their parent or a supplier
prevents it, so device_resume_noirq() sets their runtime PM status to
"active" whenever dev_pm_skip_resume() returns false. That is always
the case for PM_EVENT_RESTORE.

Nothing resumes such a device, though. If its bus or driver manages
resources from runtime PM callbacks, those resources stay off while the
device is now reported as active, and the next runtime suspend releases
them a second time.

AMBA devices are an example, since the AMBA bus only has runtime PM
callbacks, which enable and disable the APB clock. After restoring from
hibernation on a Qualcomm Glymur CRD, the runtime-suspended CoreSight
devices are marked active, and the following runtime suspend of each of
them hits:

  qdss already disabled
  WARNING: drivers/clk/clk.c:1259 at clk_core_disable+0xa4/0xac
  Call trace:
   clk_core_disable+0xa4/0xac (P)
   clk_disable+0x30/0x4c
   amba_pm_runtime_suspend+0x58/0x74
   __rpm_callback+0x48/0x1e0
   rpm_callback+0x58/0x64
   rpm_suspend+0x10c/0x5a4
   pm_runtime_work+0xc8/0xd8

followed by "qdss already unprepared".

On suspend-to-RAM this does not happen, because such devices take the
direct_complete path and device_resume_noirq() returns early for them.

Leave the runtime PM status of devices without PM callbacks as it is.

Fixes: bca84a7b93fd ("PM: sleep: Use DPM_FLAG_SMART_SUSPEND conditionally")
Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxxxxxxxx>
---
 drivers/base/power/main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 88a31e09e4f3..16a1f017051e 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -839,10 +839,15 @@ static void device_resume_noirq(struct device *dev, pm_message_t state, bool asy
 	 * Otherwise, the device is going to be resumed, so set its PM-runtime
 	 * status to "active" unless its power.smart_suspend flag is clear, in
 	 * which case it is not necessary to update its PM-runtime status.
+	 *
+	 * A device without system sleep callbacks is not going to be resumed
+	 * by anyone, though, so leave its PM-runtime status as is. Otherwise,
+	 * resources managed by its runtime PM callbacks, like the bus clock of
+	 * an AMBA device, would end up unbalanced on the next runtime suspend.
 	 */
 	if (skip_resume)
 		pm_runtime_set_suspended(dev);
-	else if (dev_pm_smart_suspend(dev))
+	else if (dev_pm_smart_suspend(dev) && !dev->power.no_pm_callbacks)
 		pm_runtime_set_active(dev);
 
 	if (dev->pm_domain) {

-- 
2.54.0