From mboxrd@z Thu Jan  1 00:00:00 1970
From: tglx@linutronix.de (Thomas Gleixner)
Date: Fri, 2 Jul 2010 17:29:52 +0200 (CEST)
Subject: [patch 2/2] arm: Implement l2x0 cache disable function
In-Reply-To: <1278071240.10162.59.camel@e102109-lin.cambridge.arm.com>
References: <20100701160206.539545857@linutronix.de>
	<20100701160352.249208135@linutronix.de>
	<1278071240.10162.59.camel@e102109-lin.cambridge.arm.com>
Message-ID: <alpine.LFD.2.00.1007021658300.2525@localhost.localdomain>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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.

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;
      }
   }

Russells patch has its own merits nevertheless as a cleanup and
simplification, but that's a separate issue.

Thoughts ?

	 tglx