id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	field_blocks	field_dependson	field_seealso
633	Do not attempt to disable branch predictors on ARM920T	Jakub Jermář	Jiri Svoboda	"The ARM920T does not have the branch predictors, yet the initialization code in loader/arch/arm32/src/asm.S contains code which attempts to disable them:

{{{
jump_to_kernel:
...
#define CP15_C1_BP              11


#ifndef PROCESSOR_ARCH_armv7_a
        mrc     p15, 0, r4, c1, c0, 0
...        
        # Disable I-cache and Branche predictors.
...
        bic     r4, r4, #(1 << CP15_C1_BP)
        
        mcr     p15, 0, r4, c1, c0, 0
#endif
}}}

ARMv4 leaves this bit (bit Z) as implementation defined. On ARM920T, bit 11 of cp15's register c1 is reserved and reads and writes as 0. The above snippet, which is executed when we have something else than ARMv7, is therefore wrong for ARMv4 and even more so for ARM920T."	defect	closed	major	0.7.0	helenos/boot/arm32	mainline	fixed	ARM920T, ARMv4, gta02