From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Thu, 28 May 2015 13:41:25 -0700 Subject: [RFC] Fix omap3 booting with thumb2 compiled kernel In-Reply-To: <6381487.LvuhvmaVk1@wuerfel> References: <20150527215545.GA30984@atomide.com> <20150528161730.GE3657@e103592.cambridge.arm.com> <20150528163605.GI30984@atomide.com> <6381487.LvuhvmaVk1@wuerfel> Message-ID: <20150528204124.GL30984@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Arnd Bergmann [150528 11:57]: > On Thursday 28 May 2015 09:36:05 Tony Lindgren wrote: > > * Dave Martin [150528 09:19]: > > > On Thu, May 28, 2015 at 07:21:25AM -0700, Tony Lindgren wrote: > > > > --- a/arch/arm/mach-omap2/sleep34xx.S > > > > +++ b/arch/arm/mach-omap2/sleep34xx.S > > > > @@ -203,23 +203,8 @@ save_context_wfi: > > > > */ > > > > ldr r1, kernel_flush > > > > blx r1 > > > > - /* > > > > - * The kernel doesn't interwork: v7_flush_dcache_all in particluar will > > > > - * always return in Thumb state when CONFIG_THUMB2_KERNEL is enabled. > > > > - * This sequence switches back to ARM. Note that .align may insert a > > > > - * nop: bx pc needs to be word-aligned in order to work. > > > > - */ > > > > - THUMB( .thumb ) > > > > - THUMB( .align ) > > > > - THUMB( bx pc ) > > > > - THUMB( nop ) > > > > - .arm > > > > - > > > > > > ^ This looks unrelated to the issue? This code is simply unnecessary > > > after Russell introduced the "ret" macro in commit 6ebbf2ce43. That > > > made v7_flush_dcache_all do a proper interworking return. > > > > > > It should probably be in a separate commit, or at least mentioned > > > explicitly in the commit log. > > > > Thanks, I've updated the description with the commit info above. > > > > I'll keep the removal of the duplicate code in this patch, as it's > > all related to the mode switching and we don't want to do it twice. > > I would have thought that the change is actually necessary after > 6ebbf2ce43, because it now returns in ARM mode, which will cause the > "bx pc; nop" thumb instruction sequence be misinterpreted as an > ARM instruction. Could be it's necessary.. But alone that change is not enough. Regards, Tony