From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Thu, 7 Jul 2011 00:09:45 +0100 Subject: [PATCH 01/10] ARM: change ARM_DMA_ZONE_SIZE into a variable In-Reply-To: References: <1309919442-20451-1-git-send-email-nicolas.pitre@linaro.org> Message-ID: <20110706230945.GA8286@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jul 05, 2011 at 11:12:16PM -0400, Nicolas Pitre wrote: > On Wed, 6 Jul 2011, Barry Song wrote: > > > 2011/7/6 Nicolas Pitre : > > > Having this value defined at compile time prevents multiple machines with > > > conflicting definitions to coexist. ?Move it to a variable in preparation > > > for having a per machine value selected at run time. ?This is relevant > > > only when CONFIG_ZONE_DMA is selected. > > > > > > Signed-off-by: Nicolas Pitre > > > > that is definitely good. i am not sure whether it will be better if > > dma zone becomes a property in memory node of DT. > > Certainly. But one thing at a time. This is the first step. Then, > those machines that are converted to DT could more easily provide the > information via this mechanism if they so desire. Actually, putting that information into DT is probably not right - you're describing something which is specific to Linux, not something which is due to hardware. What I mean is that the DMA zone is a Linux specific thing. Another OS could have a different way of dealing with the DMA restrictions (it may be possible to allocate memory within a certain set of bounds.) What is hardware specific is that the DMA devices can only address a limited range of memory. IMHO it's that which should be described in DT, not that we'll have a DMA zone of X bytes in size.