[PATCH] ARM: mx3/pcm037: properly allocate memory for mx3-camera

[Uwe Kleine-König]

Hello Russell,

On Tue, Nov 23, 2010 at 10:12:11AM +0000, Russell King - ARM Linux wrote:
> On Tue, Nov 23, 2010 at 10:43:02AM +0100, Uwe Kleine-König wrote:
> > There is no need to memzero the buffer because dma_alloc_coherent zeros
> > the memory for us.
> > 
> > This fixes:
> > 
> > 	BUG: Your driver calls ioremap() on system memory.  This leads
> > 	<4>to architecturally unpredictable behaviour on ARMv6+, and ioremap()
> > 	<4>will fail in the next kernel release.  Please fix your driver.
> > 
> > Tested-by: Michael Grzeschik <mgr at pengutronix.de>
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
> > ---
> > Hello,
> > 
> > it seems to work this way, still I'd like to have some feedback if this
> > is done right.  Russell?
> 
> Yes and probably no.  Yes, it's architecturally correct because the memory
> will be mapped only once, thereby avoiding the aliasing issue.
> 
> Probably no, because the memory is mapped strongly as device memory by
> ioremap.  ISTR whether memory remains accessible when mapped as a device
> is not something covered by the architecture, but I guess is more to do
> with how the interconnect on the SoC is setup.
> 
> In other words, we probably have gremlins lurking in
> dma_declare_coherent_memory() which could bite us at a later date.
That is, the patch is OK as such, right?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |