[Sound-open-firmware] [SOF][KERNEL] pm_runtime flow in sof

[Pierre-Louis Bossart]

> In sof-of-dev.c
> static void sof_of_probe_complete(struct device *dev)
> {
> /* allow runtime_pm */
> pm_runtime_set_autosuspend_delay(dev, SND_SOF_SUSPEND_DELAY_MS);
> pm_runtime_use_autosuspend(dev);
> pm_runtime_set_active(dev);
> pm_runtime_enable(dev);
> 
> pm_runtime_mark_last_busy(dev);
> pm_runtime_put_autosuspend(dev); 

this last line looks wrong

it looks like the code in sof-of-dev.c is imbalanced. The last
pm_runtime_put_autosuspend() is not matching any pm_runtime_get_sync(),
is it?

> }
> 
> 
> After pm_runtime_put_autosuspend,  the current device power usage count should minus one. (1->0)
> 
> And wait SND_SOF_SUSPEND_DELAY_MS seconds, sof device will autosuspend (because the power usage count is 0 ).

Indeed.

We have this comment for the PCI case:	

/* follow recommendation in pci-driver.c to decrement usage counter */
pm_runtime_put_noidle(dev);

and a matching one for remove:
/* follow recommendation in pci-driver.c to increment usage counter */
	if (snd_sof_device_probe_completed(&pci->dev) &&
	    !(sof_pci_debug & SOF_PCI_DISABLE_PM_RUNTIME))
		pm_runtime_get_noresume(&pci->dev);

In the general case, I don't know why you would need to add a
put_autosuspend in the probe complete, even for cases where the device
does support pm_runtime.

Having a mark_last_busy() is fine though, it would reset the counters
and let the autosuspend happen at a later time. But I would call this
before enable for consistency.

Can you try with the sequence below in probe_complete?

pm_runtime_set_autosuspend_delay(dev, DELAY_MS);
pm_runtime_use_autosuspend(dev);
pm_runtime_mark_last_busy(dev);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);