Re: marzen-reference doesn't boot with CONFIG_PREEMPT

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Simon,

On Wednesday 15 May 2013 12:47:16 Simon Horman wrote:
> On Wed, May 15, 2013 at 10:29:42AM +0900, Simon Horman wrote:
> > On Wed, May 15, 2013 at 03:05:18AM +0200, Laurent Pinchart wrote:
> > > On Wednesday 15 May 2013 09:23:59 Simon Horman wrote:
> > > > On Tue, May 14, 2013 at 09:08:07PM +0200, Laurent Pinchart wrote:
> > > > > But marzen does (renesas-next-20130513). Is that a known issue ?
> > > > 
> > > > No, I was not aware of that.
> > > > 
> > > > I would suspect, based on work on the kzm9g, that the problem
> > > > relates to driver initialisation order. In the case of kzm9g
> > > > my recollection is that the problem was resolved by initialising
> > > > clocksources earlier by changing their initcall level.
> > > 
> > > Did that reach mainline ? I've tried booting kzm9g-reference with
> > > CONFIG_PREEMPT and have been unable to boot it as well with renesas-
> > > next-20130513. Maybe we should enable CONFIG_PREEMPT by default to catch
> > > similar issues in the future.
> > 
> > It made it into 3.10-rc1 and has been in next for a while now.
> > So it seems that you have found a different problem.
> > 
> > I'm ambivalent to setting CONFIG_PREEMPT by default.
> 
> Hi Laurent,
> 
> I have not been able to pin-point the cause of this problem nor come up with
> a fix. However, it does seem to be related to the early initialisation of
> devices and the following work around does allow booting marzen-reference
> with CONFIG_PREEMPT.

Thank you for the workaround. What prevents this patch (or a similar patch, as 
it seems the SCIF and TMU devices would be instantiated twice) from being 
applied to mainline ? Do we have a plan regarding what code we want to keep in 
mach-shmobile and what we want to move to DT ?

> diff --git a/arch/arm/mach-shmobile/board-marzen-reference.c
> b/arch/arm/mach-shmobile/board-marzen-reference.c index f83b6d1..ac24cd7
> 100644
> --- a/arch/arm/mach-shmobile/board-marzen-reference.c
> +++ b/arch/arm/mach-shmobile/board-marzen-reference.c
> @@ -72,10 +72,11 @@ void __init marzen_init_irq(void)
>  DT_MACHINE_START(MARZEN, "marzen")
>  	.smp		= smp_ops(r8a7779_smp_ops),
>  	.map_io		= r8a7779_map_io,
> -	.init_early	= r8a7779_init_delay,
> +	.init_early	= r8a7779_add_early_devices,
>  	.nr_irqs	= NR_IRQS_LEGACY,
>  	.init_irq	= marzen_init_irq,
>  	.init_machine	= marzen_init,
>  	.init_time	= shmobile_timer_init,
>  	.dt_compat	= marzen_boards_compat_dt,
> +	.init_time      = r8a7779_earlytimer_init,
>  MACHINE_END
-- 
Regards,

Laurent Pinchart