Re: Boot hang regression 3.10.0-rc4 -> 3.10.0

[Felipe Balbi <balbi@ti.com>]

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Hi,

On Tue, Jul 09, 2013 at 11:03:54AM +0530, Rajendra Nayak wrote:
> On Monday 08 July 2013 07:05 PM, Felipe Balbi wrote:
> > Hi,
> > 
> > On Mon, Jul 08, 2013 at 06:50:01PM +0530, Rajendra Nayak wrote:
> >>>>>>>> I wonder if this is because the timeouts get now initialized to 0 instead
> >>>>>>>> of -1 for the serial driver?
> >>>>>>>>
> >>>>>>>
> >>>>>>> You meant initialized to -1, right? There's an additional check for timeout being 0. Unless i
> >>>>>>> am missing something DT-boot will start off with timeout set to 0 and then get forced to -1.
> >>>>>
> >>>>> OK
> >>>>
> >>>> Issue 2: Causing boot to stop when serial driver is initialized.
> >>>> (After Issue 1 is fixed)
> >>>>
> >>>> I could narrow this down to the change done to return -EINVAL
> >>>> instead of 0 in serial_omap_get_context_loss_count() as part of
> >>>> commit 'a630fbfbb1beeffc5bbe542a7986bf2068874633' "serial: omap:
> >>>> Fix device tree based PM runtime"
> >>>>
> >>>> What this change in turn seems to do is cause a
> >>>> serial_omap_restore_context() to get called as part of
> >>>> serial_omap_runtime_resume() which was not the case when
> >>>> serial_omap_get_context_loss_count() returned 0
> >>>>
> >>>> from serial_omap_runtime_resume():
> >>>> -----
> >>>>         int loss_cnt = serial_omap_get_context_loss_count(up);
> >>>>
> >>>>         if (loss_cnt < 0) {
> >>>>                 dev_dbg(dev, "serial_omap_get_context_loss_count failed : %d\n",
> >>>>                         loss_cnt);
> >>>>                 serial_omap_restore_context(up);
> >>>>         } else if (up->context_loss_cnt != loss_cnt) {
> >>>>                 serial_omap_restore_context(up);
> >>>>         }
> >>>> -----
> >>>>
> >>>> I am still working on why a serial_omap_restore_context() could
> >>>> have caused console to die. I will work with Sourav on this and
> >>>> post the fixes for both issue 1 and issue2 once its clear on whats
> >>>> really causing issue 2.
> >>>
> >>> That's because we don't have the omap specific pdata callbacks for
> >>> context loss any longer. We may be able to detect when the context
> >>> was really lost in the serial driver, and only then call the
> >>> serial_omap_restore_context().
> >>
> >> Right, but calling serial_omap_restore_context() even when the context
> >> is not lost, should not ideally cause an issue.
> > 
> > it does in one condition. If context hasn't been saved before. And that
> > can happen in the case of wrong pm runtime status for that device.
> > 
> > Imagine the device is marked as suspended even though it's fully enabled
> > (it hasn't been suspended by hwmod due to NO_IDLE flag). In that case
> > your context structure is all zeroes (context has never been saved
> > before) then when you call pm_runtime_get_sync() on probe() your
> > ->runtime_resume() will get called, which will restore context,
> > essentially undoing anything which was configured by u-boot.
> 
> This could be a problem for drivers which do a save context in ->runtime_suspend()
> but from what I see with omap serial, there is no save context done as part of
> ->runtime_suspend.

right, because context is "saved" in set_termios. probe() will get
called much before set_termios() has a chance to run, right ?

Same problem will trigger in that case.

I still think patch below is necessary

> > (completely untested, didn't even try to compile, just to illustrate)
> > 
> > diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c
> > index 7341eff..d8dca68 100644
> > --- a/arch/arm/mach-omap2/omap_hwmod.c
> > +++ b/arch/arm/mach-omap2/omap_hwmod.c
> > @@ -2559,6 +2559,12 @@ static void __init _setup_postsetup(struct omap_hwmod *oh)
> >  	    (postsetup_state == _HWMOD_STATE_IDLE)) {
> >  		oh->_int_flags |= _HWMOD_SKIP_ENABLE;
> >  		postsetup_state = _HWMOD_STATE_ENABLED;
> > +
> > +		/* tell pm_runtime this device is already active */
> > +		pm_runtime_set_active(&oh->od->pdev->dev);
> > +	} else {
> > +		/* tell pm_runtime this device is trully suspended */
> > +		pm_runtime_set_suspended(&oh->od->pdev->dev);
> >  	}
> >  
> >  	if (postsetup_state == _HWMOD_STATE_IDLE)

-- 
balbi

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