[PATCH 1/2] ARM: l2x0: Errata fix for flush by Wayoperationcan cause data corruption

[Santosh Shilimkar]

Thanks Will for reporting it.

> -----Original Message-----
> From: linux-arm-kernel-bounces at lists.infradead.org [mailto:linux-
> arm-kernel-bounces at lists.infradead.org] On Behalf Of Will Deacon
> Sent: Monday, March 07, 2011 5:38 PM
> To: 'Santosh Shilimkar'; Russell King - ARM Linux
> Cc: tony at atomide.com; Catalin Marinas; linux-omap at vger.kernel.org;
> linux-arm-kernel at lists.infradead.org
> Subject: RE: [PATCH 1/2] ARM: l2x0: Errata fix for flush by
> Wayoperationcan cause data corruption
>
> Hi Santosh,
>
> > > On Sun, Feb 27, 2011 at 12:00:21PM +0000, Russell King - ARM
> Linux
> > > wrote:
> > > > > +#else
> > > > > +/* Optimised out for non-errata case */
> > > > > +static inline void debug_writel(unsigned long val)
> > > > > +{
> > > > >  }
> > > >
> > > > #define l2x0_set_debug	NULL
> > > >
> > > > > +#endif
> > >
> > > I notice you got rid of the inline function.  Have you tried
> > > building this without the errata enabled?
> >
> > I accidently dropped the inline function while
> > incorporating the comment from you. :(
> >
> > Fixed it. Updated version # 6770/1
>
> This version of the patch (as it appears in -next) is broken:
>
>
> +#define debug_writel(val)	outer_cache.set_debug(val)
> +
> +static void l2x0_set_debug(unsigned long val)
> +{
> +	writel(val, l2x0_base + L2X0_DEBUG_CTRL);

This should have been "writel_relaxed()" to avoid the
cache sync.

>  }
>
> [...]
>
> @@ -119,9 +120,11 @@ static void l2x0_flush_all(void)
>
>  	/* clean all ways */
>  	spin_lock_irqsave(&l2x0_lock, flags);
> +	debug_writel(0x03);
>  	writel_relaxed(l2x0_way_mask, l2x0_base + L2X0_CLEAN_INV_WAY);
>  	cache_wait_way(l2x0_base + L2X0_CLEAN_INV_WAY, l2x0_way_mask);
>  	cache_sync();
> +	debug_writel(0x00);
>  	spin_unlock_irqrestore(&l2x0_lock, flags);
>  }
>
>
> This deadlocks because the writel forces an outer cache sync, which
> then tries to acquire the spinlock which is held by the calling
> function.
>
> If you change l2x0_set_debug to use writel_relaxed then you can
> avoid the problem.
>
Ya understood. I couldn't test non-errata case because
direct right doesn't work because of security and henced missed
it.

Below is the updated version. Also attached.

Russell,
Do you want me to push this to patch system or you can
apply this one?


Regards,
Santosh
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