From 4dee90d7b5796692e8da78c7b64cf42d5e4c1b09 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Tue, 1 Oct 2019 21:53:43 +0000 Subject: [PATCH] MIPS: genex: Don't reload address unnecessarily In ejtag_debug_handler() we must reload the address of ejtag_debug_buffer_spinlock if an sc fails, since the address in k0 will have been clobbered by the result of the sc instruction. In the case where we simply load a non-zero value (ie. there's contention for the lock) the address will not be clobbered & we can simply branch back to repeat the load from memory without reloading the address into k0. The primary motivation for this change is that it moves the target of the bnez instruction to an instruction within the LL/SC loop (the LL itself), which we know contains no other memory accesses & therefore isn't affected by Loongson3 LL/SC errata. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org Cc: Huacai Chen Cc: Jiaxun Yang Cc: linux-kernel@vger.kernel.org --- arch/mips/kernel/genex.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S index 637048e..0a43c91 100644 --- a/arch/mips/kernel/genex.S +++ b/arch/mips/kernel/genex.S @@ -355,8 +355,8 @@ NESTED(ejtag_debug_handler, PT_SIZE, sp) #ifdef CONFIG_SMP 1: PTR_LA k0, ejtag_debug_buffer_spinlock __SYNC(full, loongson3_war) - ll k0, 0(k0) - bnez k0, 1b +2: ll k0, 0(k0) + bnez k0, 2b PTR_LA k0, ejtag_debug_buffer_spinlock sc k0, 0(k0) beqz k0, 1b -- 2.7.4