Re: [PATCH v3 01/11] usb: phy: Add APIs for runtime power management

[Felipe Balbi <balbi@ti.com>]

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Hi,

On Wed, Apr 03, 2013 at 02:14:02PM -0400, Alan Stern wrote:
> > > Lets suppose DWC3 enables runtime_pm on USB 2 type phy,
> > > it will try to go into suspend state and thereby call runtime_suspend(), if any.
> > > And PHY will come to active state only when its consumer wakes it up,
> > > and this consumer is operational
> > > only when its related PHY is in fully functional state.
> > > So do we have a situation in which this PHY goes into low power state
> > > in its runtime_suspend(),
> > > resulting in non-detection of devices on further attach (since PHY is
> > > in low power state) ?
> > > 
> > > Will the controller (like EHCI/OHCI) be functional now ?
> > 
> > ehci/ohci need to cope with that by calling usb_phy_autopm_get_sync(),
> > right ? (so does DWC3 :-)
> 
> Maybe you guys have already got this all figured out -- if so, feel 
> free to ignore this email.
> 
> Some subsystems handle this issue by calling pm_runtime_get_sync() 
> before probing a driver and pm_runtime_put_sync() after unbinding the 
> driver.  If the driver is runtime-PM-enabled, it then does its own 
> put_sync near the end of its probe routine and get_sync in its release 
> routine.

sounds a bit 'fishy' to me... So a separate entity would call
pm_runtime_get_sync(), even when we don't have registered dev_pm_ops,
then drivers need to check if runtime_pm is enabled and call
pm_runtime_put*() conditionally before returning from probe(). One
remove, we might have another issue: device is already runtime_suspended
(due to e.g. autosuspend) when module is removed, a call to
pm_runtime_put_sync() will be unbalanced. No ?

-- 
balbi

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