Hi Klaus, On Mon, May 7, 2018 at 8:48 PM <klaus.go...@theobroma-systems.com> wrote:
> > On 07.05.2018, at 10:25, Chris Packham <judge.pack...@gmail.com> wrote: > > > > Hi Mans, Stefano, > > > > On Fri, Apr 27, 2018 at 9:00 PM Stefano Babic <sba...@denx.de> wrote: > > > >> On 21/04/2018 17:11, Mans Rullgard wrote: > >>> The code attempts to preserve the value of LR by storing it in R12/IP > >>> across the lowevel_init() call. However, this register is not saved > >>> by the callee. Use a register that guaranteed to be preserved instead. > >>> > >>> Signed-off-by: Mans Rullgard <m...@mansr.com> > >>> --- > >>> arch/arm/cpu/arm926ejs/start.S | 4 ++-- > >>> 1 file changed, 2 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/arch/arm/cpu/arm926ejs/start.S > > b/arch/arm/cpu/arm926ejs/start.S > >>> index 959d1ed86d8a..a6f0bdb70345 100644 > >>> --- a/arch/arm/cpu/arm926ejs/start.S > >>> +++ b/arch/arm/cpu/arm926ejs/start.S > >>> @@ -105,9 +105,9 @@ flush_dcache: > >>> /* > >>> * Go setup Memory and board specific bits prior to relocation. > >>> */ > >>> - mov ip, lr /* perserve link reg across call */ > >>> + mov r4, lr /* perserve link reg across call */ > >>> bl lowlevel_init /* go setup pll,mux,memory */ > >>> - mov lr, ip /* restore link */ > >>> + mov lr, r4 /* restore link */ > >>> #endif > >>> mov pc, lr /* back to my caller */ > >>> #endif /* CONFIG_SKIP_LOWLEVEL_INIT */ > >>> > > > >> Applied to u-boot-imx, thanks ! > > > > I think this might be causing me a problem on a Marvell Kirkwood board I'm > > working on getting into upstream. It may also be problematic for orion5x > > boards. Both of these use r4 in lowlevel_init. > > > > Obviously I can fix the board that I'm working on. Is there some > > expectation as to which registers can be clobbered? > The "Procedure Call Standard for the ARM® Architecture” may help: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf > Page 15 > A subroutine must preserve the contents of the registers r4-r8, r10, r11 and > SP (and r9 in PCS variants that designate r9 as v6). > So for thumb r1-r3 and r12 should be usable without taking any care of them. > Maybe r13 depending if you already have a stack or not. Thanks. I figured there was probably some document that described this. I started looking at EABI docs but didn't find anything last night. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot