Re: jffs2 and unaligned access

["Jon Smirl" <jonsmirl@gmail.com>]

On 5/7/08, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Wed, May 07, 2008 at 11:53:49AM +0100, David Woodhouse wrote:
>  > On Wed, 2008-05-07 at 12:27 +0200, Sascha Hauer wrote:
>  > > memcpy_from/to_io() use word aligned accesses on the io side of memory.
>  > > The MPC5200 local plus bus where our flashes are connected does not
>  > > allow unaligned accesses, so we have to use the io versions of memcpy.
>  >
>  > But this region of flash is marked as suitable for execute-in-place,
>  > otherwise the point() function wouldn't be working to give a direct
>  > pointer to it. It sounds like we shouldn't be allowing that.
>
>
> It actually is suitable for execute-in-place. It's the flash U-Boot
>  starts from. The compiler will generate a proper alignment for you.
>
>
>  >
>  > Which in turn means that perhaps we should have a property in the
>  > corresponding node in the device-tree which indicates that it's not
>  > suitable for direct access?
>
>
> So far we did not work with the device-tree flash binding but with the
>  physmap-flash driver, but ok, this is subject to change anyway.
>
>  I gave it a quick try to disable direct accesses. It works, but has a
>  1:10 performance impact on mounting a jffs2. At least it's a clean
>  solution.

How did this get resolved? The thread died without any final solution
being proposed.


>
>
>  Sascha
>
>
>
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-- 
Jon Smirl
jonsmirl@gmail.com