linux-kernel - Re: [PATCH v4 2/2] OMAP:IOMMU:flush L1 and L2 caches

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Date:	Sat, 8 Sep 2012 11:17:24 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"Gupta, Ramesh" <grgupta@...com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, tony@...mide.com
Subject: Re: [PATCH v4 2/2] OMAP:IOMMU:flush L1 and L2 caches

On Thu, Jul 05, 2012 at 10:50:24AM +0530, Gupta, Ramesh wrote:
>  static void flush_iopgd_range(u32 *first, u32 *last)
>  {
> -	/* FIXME: L2 cache should be taken care of if it exists */
> -	do {
> -		asm("mcr	p15, 0, %0, c7, c10, 1 @ flush_pgd"
> -		    : : "r" (first));
> -		first += L1_CACHE_BYTES / sizeof(*first);
> -	} while (first <= last);
> +	flush_iommu_mem(first, last);
> +	outer_flush_range(virt_to_phys(first), virt_to_phys(last));

I think this would be safer if these operated on an area rather than a
range - which means taking a start plus size.

	phys_addr_t phys = virt_to_phys(start);

	iommu_flush_area(start, size);
	outer_flush_range(phys, phys + size);

is safer than the above if virt_to_phys() is non-linear.

>  		*iopgd = virt_to_phys(iopte) | IOPGD_TABLE;
> -		flush_iopgd_range(iopgd, iopgd);
> +		flush_iopgd_range(iopgd, iopgd + 1);

And operating on a start + size also makes this kind of stuff clearer.
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