linux-kernel - Re: [PATCH] ARM: omap2: drop broken broadcast timer hack

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Date:   Thu, 28 May 2020 13:38:10 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        arm-soc <arm@...nel.org>, Rob Herring <robh@...nel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Lokesh Vutla <lokeshvutla@...com>, Keerthy <j-keerthy@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tero Kristo <t-kristo@...com>, Olof Johansson <olof@...om.net>,
        linux-omap <linux-omap@...r.kernel.org>,
        afzal mohammed <afzal.mohd.ma@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: omap2: drop broken broadcast timer hack

* Arnd Bergmann <arnd@...db.de> [200528 20:35]:
> On Thu, May 28, 2020 at 6:18 PM <santosh.shilimkar@...cle.com> wrote:
> > On 5/28/20 8:57 AM, Tony Lindgren wrote:
> > > * Tony Lindgren <tony@...mide.com> [200528 13:51]:
> > >> * Tony Lindgren <tony@...mide.com> [200528 13:47]:
> > >>> * Arnd Bergmann <arnd@...db.de> [200528 09:20]:
> > >>>> The OMAP4 timer code had a special hack for using the broadcast timer
> > >>>> without SMP. Since the dmtimer is now gone, this also needs to be dropped
> > >>>> to avoid a link failure for non-SMP AM43xx configurations:
> > >>>>
> > >>>> kernel/time/tick-broadcast.o: in function `tick_device_uses_broadcast':
> > >>>> tick-broadcast.c:(.text+0x130): undefined reference to `tick_broadcast'
> > >>>
> > >>> Hmm this sounds like a regression though. Isn't this needed for using
> > >>> the ARM local timers on non-SMP SoC, so a separate timer from dmtimer?
> > >>>
> > >>> I've probably removed something accidentally to cause this.
> > >>
> > >> Sounds like arch/arm/mach-omap2/Makefile change needs to be removed
> > >> to always still build in timer.o. And probably timer.c needs back
> > >> the ifdef for CONFIG_SOC_HAS_REALTIME_COUNTER.
> > >>
> > >> I'll take a look today.
> > >
> > > I've sent a patch along those lines as:
> > >
> > > [PATCH] ARM: OMAP2+: Fix regression for using local timer on non-SMP SoCs
> > >
> > > A link for the patch at [0] below.
> > >
> > CPU local timers not being in always ON power domain use to be the
> > reason on early version of the SOCs but later SOC moved the CPU local
> > timer also in always on domain. Probably AM43xx does loose local timer
> > on CPU PD in low power so yes broadcast would be needed with dmtimer
> > help.
> >
> > >
> > > [0] https://lore.kernel.org/linux-omap/20200528155453.8585-1-tony@atomide.com/T/#u
> > >
> > This should restore it.
> 
> Should I apply the fix directly to the arm/soc branch that has the
> other changes then?

Sure please do, that saves a single-fix pull request.

Regards,

Tony