[PATCH] ARM: mx3/pcm037: properly allocate memory for mx3-camera
maramaopercheseimorto at gmail.com
Tue Nov 23 09:08:49 EST 2010
On mar, 2010-11-23 at 11:26 +0100, Uwe Kleine-König wrote:
> 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
I'm trying to achieve the camera support for the i.MX31 3-Stack board.
The camera driver is in an early stage and results are not as expected
(I have to solve some timing issues).
Adding the dma reservation code as you do in this patch results in
system freeze when the capture chain is activated..
- Greg Kroah-Hartman (FOSDEM 2010)
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