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    SubjectRe: lockdep warning in urb.c:363 usb_submit_urb
    On 03/25/20 22:28, Rafael J. Wysocki wrote:
    > On Wed, Mar 25, 2020 at 9:49 PM Alan Stern <stern@rowland.harvard.edu> wrote:
    > >
    > > On Wed, 25 Mar 2020, Qais Yousef wrote:
    > >
    > > > Thanks for all the hints Alan.
    > > >
    > > > I think I figured it out, the below patch seems to fix it for me. Looking
    > > > at other drivers resume functions it seems we're missing the
    > > > pm_runtime_disable()->set_active()->enable() dance. Doing that fixes the
    > > > warning and the dev_err() in driver/base/power.
    > >
    > > Ah, yes. This should have been added years ago; guess I forgot. :-(
    > >
    > > > I don't see xhci-plat.c doing that, I wonder if it needs it too.
    > > >
    > > > I'm not well versed about the details and the rules here. So my fix could be
    > > > a hack, though it does seem the right thing to do.
    > > >
    > > > I wonder why the power core doesn't handle this transparently..
    > >
    > > Initially, we didn't want the PM core to do this automatically because
    > > we thought some devices might want to remain runtime-suspended
    > > following a system resume, and only the device driver would know what
    > > to do.
    > >
    > > Raphael, now that we have the direct_complete mechanism, can we revisit
    > > this? Should the PM core automatically call pm_runtime_set_active() if
    > > dev->power.direct_complete isn't set? Perhaps in device_resume_early()
    > > prior to the pm_runtime_enable() call?
    > >
    > > It's possible we discussed this and decided against it at the time when
    > > direct_complete was added, but if so I don't remember what was said.
    >
    > Me neither. :-)
    >
    > That said complexity has grown since then and there are the
    > DPM_FLAG_SMART_SUSPEND and DPM_FLAG_LEAVE_SUSPENDED flags that can be
    > used to control that behavior to some extent.
    >
    > Setting DPM_FLAG_SMART_SUSPEND alone, in particular, causes
    > pm_runtime_set_active() to be called at the noirq stage of device
    > resume either by the core or by bus types (e.g. PCI) etc.
    >
    > It looks like ohci-platform might use DPM_FLAG_SMART_SUSPEND, but I
    > need to take a closer look at that (possibly later this week).

    Okay I take it this was root caused correctly and now it's a question of which
    is a better fix.

    Thanks!

    --
    Qais Yousef

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