From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Tue, 23 Nov 2010 11:26:32 +0100 Subject: [PATCH] ARM: mx3/pcm037: properly allocate memory for mx3-camera In-Reply-To: <20101123101210.GA18170@n2100.arm.linux.org.uk> References: <20101011152516.GF27153@n2100.arm.linux.org.uk> <1290505382-16110-1-git-send-email-u.kleine-koenig@pengutronix.de> <20101123101210.GA18170@n2100.arm.linux.org.uk> Message-ID: <20101123102632.GM4693@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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-K?nig 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 > > Signed-off-by: Uwe Kleine-K?nig > > --- > > 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-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |