ARCv2: LLSC: software backoff is NOT needed starting HS2.1c

BugLink: http://bugs.launchpad.net/bugs/1607404

commit b31ac426 upstream.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

arch/arc/Kconfig

@@ -387,7 +387,7 @@ config ARC_HAS_LLSC
 
 config ARC_STAR_9000923308
 	bool "Workaround for llock/scond livelock"
-	default y
+	default n
 	depends on ISA_ARCV2 && SMP && ARC_HAS_LLSC
 
 config ARC_HAS_SWAPE

arch/arc/kernel/setup.c

@@ -332,11 +332,6 @@ static void arc_chk_core_config(void)
 		pr_warn("CONFIG_ARC_FPU_SAVE_RESTORE needed for working apps\n");
 	else if (!cpu->extn.fpu_dp && fpu_enabled)
 		panic("FPU non-existent, disable CONFIG_ARC_FPU_SAVE_RESTORE\n");
-
-	if (is_isa_arcv2() && IS_ENABLED(CONFIG_SMP) && cpu->isa.atomic &&
-	    IS_ENABLED(CONFIG_ARC_HAS_LLSC) &&
-	    !IS_ENABLED(CONFIG_ARC_STAR_9000923308))
-		panic("llock/scond livelock workaround missing\n");
 }
 
 /*