From mboxrd@z Thu Jan  1 00:00:00 1970
From: catalin.marinas@arm.com (Catalin Marinas)
Date: Fri, 02 Jul 2010 17:10:10 +0100
Subject: [patch 2/2] arm: Implement l2x0 cache disable function
In-Reply-To: <alpine.LFD.2.00.1007021658300.2525@localhost.localdomain>
References: <alpine.LFD.2.00.1007021658300.2525@localhost.localdomain>
Message-ID: <1278087010.10162.271.camel@e102109-lin.cambridge.arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, 2010-07-02 at 16:29 +0100, Thomas Gleixner wrote:
> On Fri, 2 Jul 2010, Catalin Marinas wrote:
> 
> > On Thu, 2010-07-01 at 17:05 +0100, Thomas Gleixner wrote:
> > > This function is called from kexec code before the inner caches are
> > > disabled to prevent random crashes in the new kernel.
> > >
> > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > > Index: linux-2.6/arch/arm/mm/cache-l2x0.c
> > > ===================================================================
> > > --- linux-2.6.orig/arch/arm/mm/cache-l2x0.c
> > > +++ linux-2.6/arch/arm/mm/cache-l2x0.c
> > > @@ -206,6 +206,12 @@ static void l2x0_flush_range(unsigned lo
> > >         spin_unlock_irqrestore(&l2x0_lock, flags);
> > >  }
> > >
> > > +static void l2x0_cache_disable(void)
> > > +{
> > > +       l2x0_inv_all();
> > > +       writel(0, l2x0_base + L2X0_CTRL);
> > > +}
> >
> > Even if we go this route, we need an l2x0_flush_all() rather than
> > invalidate here as the latter removes dirty cache lines without evicting
> > them first.
> 
> True, but that's an implementation detail. What's more important is to
> make a decision how to solve the problem as kexec is completely
> unusable for all L2 systems right now.

My view is that we should try to find why cache flushing doesn't work
but unfortunately I don't have any spare time to look into this (would
need to use tools like ICE debugging/tracing).

> I think the correct way to deal with this is disabling L2 and let the
> OMAP3 folks deal with it. As Tony said there is some SMI magic to do
> that, so we can do the following:
> 
> In l2x0_init()
> 
>    if (!l2_enabled()) {
>       if (non_secure()) {
>          omap_smi_magic_l2_enable();
>          outer_cache.disable = omap_smi_magic_l2_disable;
>       } else {
>          sane_l2_enable();
>          outer_cache.disable = sane_l2_disable;
>       }
>    }

The non_secure() bit is the key. AFAIK there isn't an easy way to check
whether you are running in secure or non-secure mode (I think there is
some CP14 debug register telling this but those registers aren't
mandatory in a CPU implementation).

-- 
Catalin