Boot hang regression 3.10.0-rc4 -> 3.10.0

[Felipe Balbi]

Hi,

On Wed, Jul 10, 2013 at 03:16:54PM +0300, Grygorii Strashko wrote:
> >>>>>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)
> >>>
> >>
> >>This will not work - _setup_postsetup() is called from core_initcall
> >>level and OMAP devices have not been created at this moment yet
> >>(of_platform_populate() is called from
> >>customize_machine->init_machine->omap_generic_init() at arch_initcall time)
> >
> >fair enough, but something *like* that needs to be done. If pm_runtime
> >doesn't know the state of the device by the time pm_runtime_enable() is
> >called, the wrong assumptions might be made and we will forever have
> >such problems as our ->runtime_resume() callback being called when it
> >shouldn't.
> >
> >>More over, I don't recommend to depend on hwmod->od field - it's been
> >>created to support OPPs and it's obsolete now in case of DT use.
> >
> >that's alright, but still we need something similar.
> >
> >But in any case, if on DT boot that's not used, than *what* uses
> >HWMOD_INIT_NO_IDLE during DT boot ?
> >
> >There's a single place in kernel source which checks if
> >HWMOD_INIT_NO_IDLE is set, and that's the place which I patched.
> >
> >We, certainly, need a way to tell pm_runtime if the device is active or
> >suspended by the time we reach our probe() function. Either we assume
> >*all* devices are active and we blindly call pm_runtime_set_active() for
> >all devices, or we assume *all* devices are suspended as we call
> >pm_runtime_set_suspend() for all devices, or we figure out which ones
> >are active and which are not and call pm_runtime_set_{active,suspend}()
> >conditionally.
> >
> >>Seems, This issue need to be handled in driver for DT boot use case,
> >>possibly cmdline need to be parsed in the same way as it's done in
> >>omap_serial_early_init().
> >
> >so you want *every* single driver to parse their own cmdline ? How big
> >would the cmdline become ? This makes no sense.
> >
> 
> Agree here. Seems there two similar issues:
> - this one with omap_serial
> - GPIO reset issue http://www.spinics.net/lists/linux-omap/msg84186.html
>   (similar issue is observed on OMAP4460+TPS6236x)
> 
> And I think, that HWMOD_INIT_NO_IDLE and HWMOD_INIT_NO_RESET flags
> can't be treated as
> SoC (IP) specific parameters any more - they should be board specific.
> 
> I think, some kind of board_layout {} DT definition need to be
> created to solve these issues (just an idea). For example:
> 
> Board DTS file:
> board_layout {
>  ti,hwmods-init-no-reset = "gpio1", "uart3";
>  ti,hwmods-init-no-idle = "uart3";
> }

nah... if we go down the path of passing this info via DT, all you need
to pass is some information if the IP should be reset/idled or not
during initialization.

-- 
balbi
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