linux-kernel - Re: [PATCH v2 00/20] rtc: omap: fixes and power-off feature

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Message-ID: <20141024192948.GE11455@saruman>
Date:	Fri, 24 Oct 2014 14:29:48 -0500
From:	Felipe Balbi <balbi@...com>
To:	Felipe Balbi <balbi@...com>
CC:	Johan Hovold <johan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Tony Lindgren <tony@...mide.com>,
	Benoît Cousson <bcousson@...libre.com>,
	Lokesh Vutla <lokeshvutla@...com>,
	Guenter Roeck <linux@...ck-us.net>, <nsekhar@...com>,
	<t-kristo@...com>, <j-keerthy@...com>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <rtc-linux@...glegroups.com>,
	<linux-kernel@...r.kernel.org>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH v2 00/20] rtc: omap: fixes and power-off feature

Hi,

On Fri, Oct 24, 2014 at 02:25:40PM -0500, Felipe Balbi wrote:
> On Fri, Oct 24, 2014 at 09:02:51PM +0200, Johan Hovold wrote:
> > [ +CC: Russell ]
> > 
> > On Fri, Oct 24, 2014 at 11:08:45AM -0500, Felipe Balbi wrote:
> > 
> > > I tested this entire series with my BBB and it still works fine. However
> > > I still get below panic. This time without any DRM errors:
> > > 
> > > [   63.087832] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> > > [   63.087832] 
> > > [   63.097399] CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 3.18.0-rc1-00095-g8524e69 #556
> > > [   63.106060] [<c00175a4>] (unwind_backtrace) from [<c00132f0>] (show_stack+0x20/0x24)
> > > [   63.114160] [<c00132f0>] (show_stack) from [<c0657404>] (dump_stack+0x8c/0xa4)
> > > [   63.121706] [<c0657404>] (dump_stack) from [<c0654f70>] (panic+0xa0/0x220)
> > > [   63.128895] [<c0654f70>] (panic) from [<c0049e64>] (do_exit+0x974/0x9d0)
> > > [   63.135900] [<c0049e64>] (do_exit) from [<c006775c>] (SyS_reboot+0x14c/0x1e8)
> > > [   63.143361] [<c006775c>] (SyS_reboot) from [<c000f080>] (ret_fast_syscall+0x0/0x48)
> > > [   63.151596] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> > > 
> > > Then again, this also happens by simply calling poweroff without
> > > enabling wakealarm.
> > 
> > Bah, I forgot to look into that. I haven't seen this myself as I don't
> > use systemd (which does the syscall from process 0).
> > 
> > Some driver power-off implementations and some arch machine_power_off
> > spin indefinitely (or use an mdelay and WARN) after trying to power off.
> > 
> > I think this is really a bug in arch/arm that should be fixed
> > analogously to how failed reboot is handled in machine_restart().
> > 
> > Care to try the patch below?
> > 
> > I should still add a two-second delay to rtc-omap to avoid the arch
> > error message.
> > 
> > Andrew, can you update one patch in the series or should I just resend
> > them all (with proper Tested-by tags)?
> > 
> > > In any case, for the whole series:
> > > 
> > > Tested-by: Felipe Balbi <balbi@...com>
> > 
> > Thanks for testing!
> > 
> > Johan
> > 
> > 
> > >From aaa1d1d6171c895b6966ba5b738ac7946ada97c7 Mon Sep 17 00:00:00 2001
> > From: Johan Hovold <johan@...nel.org>
> > Date: Fri, 24 Oct 2014 18:53:09 +0200
> > Subject: [PATCH] ARM: fix failed power-off handling
> > 
> > Make sure to handle failed power off by printing an error message and
> > halting (analogously to how failed reboot is handled).
> > 
> > Power off can fail for example if the hardware has not been wired up
> > correctly.
> > 
> > This avoids a kernel panic when called from process 0:
> > 
> > [   63.087832] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> > [   63.087832]
> > [   63.097399] CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 3.18.0-rc1-00095-g8524e69 #556
> > [   63.106060] [<c00175a4>] (unwind_backtrace) from [<c00132f0>] (show_stack+0x20/0x24)
> > [   63.114160] [<c00132f0>] (show_stack) from [<c0657404>] (dump_stack+0x8c/0xa4)
> > [   63.121706] [<c0657404>] (dump_stack) from [<c0654f70>] (panic+0xa0/0x220)
> > [   63.128895] [<c0654f70>] (panic) from [<c0049e64>] (do_exit+0x974/0x9d0)
> > [   63.135900] [<c0049e64>] (do_exit) from [<c006775c>] (SyS_reboot+0x14c/0x1e8)
> > [   63.143361] [<c006775c>] (SyS_reboot) from [<c000f080>] (ret_fast_syscall+0x0/0x48)
> > [   63.151596] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> > 
> > Signed-off-by: Johan Hovold <johan@...nel.org>
> > ---
> >  arch/arm/kernel/process.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> > index a35f6ebbd2c2..68c38af5687c 100644
> > --- a/arch/arm/kernel/process.c
> > +++ b/arch/arm/kernel/process.c
> > @@ -212,6 +212,12 @@ void machine_power_off(void)
> >  
> >  	if (pm_power_off)
> >  		pm_power_off();
> > +
> > +	/* Give a grace period for failure to power off */
> > +	mdelay(1000);
> > +
> > +	pr_err("Power off failed -- system halted\n");
> > +	while (1);
> >  }
> 
> with this I always get to "Power off failed -- system halted". If I
> switch to v3.18-rc1 vanilla, then it works. So it's definitely caused by
> your rtc-only patches.

ok, so it seems like it takes more than 1 second for things to
propagate. If I increase that mdelay() to 3000, then everything works
fine on my end. I think we should get RMK's input on this 3000ms delay
to machine_power_off(). Should it be generic, or should we add it to our
rtc pm_power_off implementation ?

-- 
balbi

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