[U-Boot] CPU Sleep in ARM Cortex A8
Hi, I want to know what is the instruction for sleeping in ARM Cortex A8. I did execute a WFI instruction seems to be a NOP. void cpu_idle() { unsigned long tmp = 0; asm("b 1f\n\t" ".align 5\n\t" "1:\n\t" "mcr p15, 0, %0, c7, c10, 5\n\t" "mcr p15, 0, %0, c7, c10, 4\n\t" "mcr p15, 0, %0, c7, c0, 4" :: "r" (tmp)); return; } The above function doesnt seem to work. Please let me know exact instructions to follow.
Warm Regards, Akshay
Keep up with people you care about with Yahoo! India Mail. Learn how. http://in.overview.mail.yahoo.com/connectmore
Hi
2009/10/12 akshay ts takshays@yahoo.co.in:
Hi, I want to know what is the instruction for sleeping in ARM Cortex A8. I did execute a WFI instruction seems to be a NOP. void cpu_idle() { unsigned long tmp = 0; asm("b 1f\n\t" ".align 5\n\t" "1:\n\t" "mcr p15, 0, %0, c7, c10, 5\n\t" "mcr p15, 0, %0, c7, c10, 4\n\t" "mcr p15, 0, %0, c7, c0, 4" :: "r" (tmp)); return; } The above function doesnt seem to work. Please let me know exact instructions to follow.
Well, the idle-code in Linux looks like: /* * cpu_v7_do_idle() * * Idle the processor (eg, wait for interrupt). * * IRQs are already disabled. */ ENTRY(cpu_v7_do_idle) dsb @ WFI may enter a low-power mode wfi mov pc, lr ENDPROC(cpu_v7_do_idle)
So you may want to try that instead.
Hi all, I am getting the following error while building using ARMV7 toolchain.
{standard input}:599: Error: selected processor does not support `ldrex r1,[r2]' {standard input}:601: Error: selected processor does not support `strex r3,r1,[r2]'
For example the following code uses strex and ldrex but it is not specified which register to use. atomic_inc in turn uses ->
static inline int atomic_add_return(int i, atomic_t *v) { unsigned long tmp; int result;
__asm__ __volatile__("@ atomic_add_return\n" "1: ldrex %0, [%2]\n" " add %0, %0, %3\n" " strex %1, %0, [%2]\n" " teq %1, #0\n" " bne 1b" : "=&r" (result), "=&r" (tmp) : "r" (&v->counter), "Ir" (i) : "cc");
return result; }
According to arm architecture reference manual strex/ldrex are valid for ARMV6 and above.
The above code i copied from kernel and it is building in kernel.
I dont know how to solve this issue Any toolchain specific CFLAGS/attributes i need to set/unset. Please Help
Warm Regards, Akshay
Yahoo! India has a new look. Take a sneak peek http://in.yahoo.com/trynew
participants (2)
-
akshay ts -
Magnus Lilja