Arm9-low Power Consumption

In the arm9-core, one of the methods to achieve low power consumption can be managed through MMU. Add the following code to the idle task :. section _ cache_asm. global _ mmuwaitforinterrupt;/* The system kernel enters the low power mode. */;/* Wait For FIQ/IRQ to activate */. func _ mmuwaitforinterrupt:;/* arm enters the energy-saving state and waits for interruption */movr0, 0mcrp15, 0, R0, C7, C0, 4 movpc, LR. the endfunc uses the arm926 kernel as an example. Linux Kernel implementation in arch/ARM/MM/proc-arm926.S files: 97/* 98 * cpu_arm926_do_idle () # idle task 99*100 * called with irqs disabled101 */102. align 10103 entry (cpu_arm926_do_idle) 104 mov r0, #0105 MRC P15, 0, R1, C1, C0, 0 @ read control register106 MCR P15, 0, R0, C7, C10, 4 @ drain write buffer107 Bic R2, R1, #1 <12108 Mrs R3, CPSR @ disable fiqs while icache109 Orr IP, R3, # psr_f_bit @ is disabled110 MSR cpsr_c, ip111 MCR P15, 0, R2, C1, C0, 0 @ disable I cache112 MCR P15, 0, R0, C7, C0, 4 @ wait for interrupt113 MCR P15, 0, R1, c1, C0, 0 @ restore icache enable114 MSR cpsr_c, R3 @ restore FIQ state115 mov PC, lr116