Re: [PATCH] Avoid SDRAM access crash

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Jul 03, 2012 at 07:22:57AM -0400, Steve Schefter wrote:
> Hi Sascha.
> 
> >I wonder why this has never hit me. On what hardware did you see this?
> 
> Me too.  All I can say is that the timing is tight.  I see crashes
> at various DRAM addresses, all depending on how much was left in
> cache when the tlb invalidate was done.
> 
> I'm using the Phytec phyCORE-OMAP44xx card.
> 
> >Does the following patch solve your problem aswell?
> 
> It does.  I see that routine contains a cache flush as well.

Ok, thanks for testing. I applied my version because it flushes only
the relevant parts of the cache and looks more like C ;)

Sascha

> 
> Regards,
> 	Steve
> 
> >
> >8<----------------------------------------------------
> >
> >ARM mmu: flush page tables in arm_mmu_remap_sdram()
> >
> >Signed-off-by: Sascha Hauer<s.hauer@pengutronix.de>
> >---
> >  arch/arm/cpu/mmu.c |    5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> >diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
> >index 55b07a4..607f357 100644
> >--- a/arch/arm/cpu/mmu.c
> >+++ b/arch/arm/cpu/mmu.c
> >@@ -147,7 +147,7 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
> >  	if ((phys&  (SZ_1M - 1)) || (bank->size&  (SZ_1M - 1)))
> >  		return -EINVAL;
> >
> >-	ptes = memalign(0x400, num_ptes * sizeof(u32));
> >+	ptes = memalign(PAGE_SIZE, num_ptes * sizeof(u32));
> >
> >  	debug("ptes: 0x%p ttb_start: 0x%08lx ttb_end: 0x%08lx\n",
> >  			ptes, ttb_start, ttb_end);
> >@@ -165,6 +165,9 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
> >  		pte += 256;
> >  	}
> >
> >+	dma_flush_range((unsigned long)ttb, (unsigned long)ttb + 0x4000);
> >+	dma_flush_range((unsigned long)ptes, num_ptes * sizeof(u32));
> >+
> >  	tlb_invalidate();
> >
> >  	return 0;
> 

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