Hi, On Thu, Apr 04, 2013 at 02:26:51PM +0530, Vivek Gautam 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 ? > > May be i am misinterpreting !! > If PHYs are runtime-PM enabled (PHY probe calls *runtime_enable*), > then the consumers > need to call pm_runtime_get_sync whever they want to access PHY. Alright, so here's my understanding: I suggested letting e.g. DWC3 enable the PHY's runtime_pm; Alan said that it could be done before that so that DWC3 sees an enabled PHY during probe. -- balbi
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