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Message-ID: <4A5B5640.2050308@googlemail.com>
Date: Mon, 13 Jul 2009 17:44:00 +0200
From: Dirk Behme <dirk.behme@googlemail.com>
User-Agent: Thunderbird 2.0.0.22 (X11/20090605)
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To: Catalin Marinas <catalin.marinas@arm.com>
CC: Russell King - ARM Linux <linux@arm.linux.org.uk>,
       Sudeep K N <sudeepholla.maillist@gmail.com>,
       linux-arm-kernel@lists.arm.linux.org.uk, drzeus-mmc@drzeus.cx,
       linux-kernel@vger.kernel.org
Subject: Re: Rootfs in eMMC: Kernel panic ...Attempted to kill init!
References: <20090622164604.GG29188@n2100.arm.linux.org.uk> <1245767657.16488.38.camel@pc1117.cambridge.arm.com>
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Hi Catalin,

Catalin Marinas wrote:
> On Mon, 2009-06-22 at 17:46 +0100, Russell King - ARM Linux wrote:
>> On Mon, Jun 22, 2009 at 05:13:16PM +0100, Catalin Marinas wrote:
>>> In my case (ext2 over pata_platform), there is no flush_dcache_page()
>>> call after the page was written with data from the CompactFlash (neither
>>> the driver nor the VFS layer do this and we used hardware tracing to
>>> double-check). When the page is mapped into user space,
>>> update_mmu_cache() is called but the page hasn't been marked as dirty
>>> and no D-cache flushing occurs. Calling flush_dcache_page() in
>>> mpage_end_io_read() works around this issue.
>> As already covered, there's no chance of adding such a call to the
>> generic kernel.  It's the responsibility of the drivers to ensure that
>> data they read in hits the underlying page - in the same way that DMA
>> does.
> 
> The patch below appears to solve the problem with CompactFlash using
> pata_platform (I cc'ed linux-ide since the patch changes their code).
> The patch only handles the read case but similarly it may need to handle
> the write case if D-cache aliasing between user and kernel mappings
> exists.
> 
> For the USB mass storage, I haven't yet figured out the best place to
> call flush_dcache_page().

Any news regarding USB mass storage on ARM MPCore? Else this would 
mean that USB mass storage (USB stick, USB disk) formatted with 
ext2/3/4 wouldn't work with MPCore?

Many thanks and best regards

Dirk
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