From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Thu, 2 Jun 2011 21:16:11 +0100 Subject: using identity_mapping_add & switching MMU state - how ? In-Reply-To: References: Message-ID: <20110602201611.GA10532@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jun 02, 2011 at 04:44:02PM +0100, Frank Hofmann wrote: > I'm trying to find a way to do an MMU off / on transition. > > What I want to do is to call cpu_do_resume() from the hibernation restore > codepath. > > I've succeeded to make this work by adding a test whether the MMU is > already on when cpu_resume_mmu() is called. I think you're making things more complicated than they need to be. > I'm not sure that sort of thing is proper; hence I've been trying to find > a way to disable the MMU before calling cpu_do_resume(). Well, I don't really condone using cpu_do_resume() outside of its original context of arch/arm/kernel/sleep.S - the two were written to work together, and the processor specific bit is not really designed to be used separately. > Can't seem to get this to work though; even though I'm creating a > separate MMU context that's given 1:1 mappings for all of kernel > code/data, execution still hangs as soon as I enable the code section > below that switches the MMU off. I'm not surprised - cpu_do_resume() has some special entry requirements which are not obvious by way of the rest of the code in arch/arm/kernel/sleep.S. As I say, cpu_do_resume is not designed to be used by other code other than what's in that file. But... it requires the v:p offset in r1, and the _virtual_ address of the code to continue at in lr. These are specifically saved for it by cpu_suspend in arch/arm/kernel/sleep.S.