linux-kernel - Re: [PATCH] OMAP: iommu flush page table entries from L1 and L2 cache

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Message-ID: <20110418110502.GI12272@atomide.com>
Date:	Mon, 18 Apr 2011 14:05:08 +0300
From:	Tony Lindgren <tony@...mide.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Fernando Guzman Lugo <fernando.lugo@...com>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Ramesh Gupta <grgupta@...com>,
	Hari Kanigeri <h-kanigeri2@...com>,
	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
Subject: Re: [PATCH] OMAP: iommu flush page table entries from L1 and L2
 cache

* Arnd Bergmann <arnd@...db.de> [110418 10:26]:
> On Friday 15 April 2011, Russell King - ARM Linux wrote:
> > On Thu, Apr 14, 2011 at 04:52:48PM -0500, Fernando Guzman Lugo wrote:
> > > From: Ramesh Gupta <grgupta@...com>
> > > 
> > > This patch is to flush the iommu page table entries from L1 and L2
> > > caches using dma_map_single. This also simplifies the implementation
> > > by removing the functions  flush_iopgd_range/flush_iopte_range.
> > 
> > No.  This usage is just wrong.  If you're going to use the DMA API then
> > unmap it, otherwise the DMA API debugging will go awol.
> 
> 
> It's also completely upside-down: The iommu support should provide interfaces
> using the dma-mapping API, not use that API to provide a machine specific
> version of the generic interface.
> 
> As far as I can tell, nothing actually uses these drivers, maybe we should just
> remove them before we get any code in the mainline kernel that depends on it.

There is drivers/media/video/omap3isp/isp.c. But if we now
have a generic replacement for this code we should start using it.

Hiroshi, any comments on that?

Regards,

Tony
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