From mboxrd@z Thu Jan 1 00:00:00 1970 From: grant.likely@secretlab.ca (Grant Likely) Date: Fri, 26 Mar 2010 12:13:39 -0600 Subject: RFC: ARM Boot standard for passing device tree blob In-Reply-To: <4BACF238.3040405@firmworks.com> References: <20100325210409.GH24984@n2100.arm.linux.org.uk> <1269610665.807.51.camel@e102109-lin.cambridge.arm.com> <4BACF238.3040405@firmworks.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Mar 26, 2010 at 11:43 AM, Mitch Bradley wrote: > Catalin Marinas wrote: >> On Thu, 2010-03-25 at 21:04 +0000, Russell King - ARM Linux wrote: >>> On Wed, Mar 24, 2010 at 09:11:56AM -0600, Grant Likely wrote: >>>> *IRQs disabled >>>> *MMU off >>>> *Instruction cache either on or off >>>> *Data cache turned off >>> >>> Would recommend saying "Data cache(s) turned off" so that L2 cache is >>> included. >> >> There are platforms where the L2 cache is turned on by the boot monitor >> (secure monitor) and Linux has no control over it (I think OMAP). > > What is the reason for turning off the data caches? ?Leaving all caches > turned on and coherent with one another has always worked well for me at the > interface from firmware to a booted program. Data cache off is specified in Documentation/arm/Booting in the Linux source tree and I used that document as a starting point to get discussion going. I don't have a technical argument either way. Russell, what is the reason for having the data cache off? g.