From 9002062ff52696888847224a778a3279bc8c1cb5 Mon Sep 17 00:00:00 2001 From: Michal Simek Date: Mon, 31 Aug 2009 16:24:56 +0200 Subject: microblaze: Improve checking mechanism for MSR instruction It is more safe to use clear instead of msrset. We save some instructions too. Signed-off-by: Michal Simek --- arch/microblaze/kernel/head.S | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) (limited to 'arch/microblaze') diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S index bfc7ea801cc..697ce3007f3 100644 --- a/arch/microblaze/kernel/head.S +++ b/arch/microblaze/kernel/head.S @@ -54,19 +54,16 @@ ENTRY(_start) mfs r1, rmsr andi r1, r1, ~2 mts rmsr, r1 - /* * Here is checking mechanism which check if Microblaze has msr instructions * We load msr and compare it with previous r1 value - if is the same, * msr instructions works if not - cpu don't have them. */ - or r8, r0, r0 /* 0 - I have msr instr, 1 - I don't have */ - or r12, r0, r0 - msrset r12, 0 /* set nothing - just read msr for test */ - cmpu r12, r12, r1 - beqi r12, 1f - ori r8, r0, 1 /* I don't have msr */ -1: + /* r8=0 - I have msr instr, 1 - I don't have them */ + rsubi r0, r0, 1 /* set the carry bit */ + msrclr r0, 0x4 /* try to clear it */ + /* read the carry bit, r8 will be '0' if msrclr exists */ + addik r8, r0, 0 /* r7 may point to an FDT, or there may be one linked in. if it's in r7, we've got to save it away ASAP. -- cgit v1.2.3-70-g09d2