Albert, >> >> 1) In relocate_new_kernel, you put the comment saying switch the >>MMU off. Can you tell me how these code can achieve it. I don't see it >>happens on FSL85xx(actually 85xx or 44x doesn't allow MMU to turn off). >> >> + .globl relocate_new_kernel >> +relocate_new_kernel: >> + /* r3 = page_list */ >> + /* r4 = reboot_code_buffer */ >> + /* r5 = start_address */ >> + >> + li r0, 0 >> + >> + /* >> + * Set Machine Status Register to a known status, >> + * switch the MMU off and jump to 1: in a single step. >> + */ >> + >> + mr r8, r0 >> + ori r8, r8, MSR_RI|MSR_ME >> + mtspr SRR1, r8 >> + addi r8, r4, 1f - relocate_new_kernel >> + mtspr SRR0, r8 >> + sync >> + rfi >This code sets the MSR to a value where MSR_IR (Instruction Relocate) and >MSR_DI (Data Relocate) are cleared, and thus the MMU is turned effectively >off. >Turning the MMU off is possible at least on 6xx and 7xx. I don't understand why you choose to turn the MMU off on ppc. Is there any practical reason? On Freescale 85xx which is close to PPC44x, I did not turn off MMU(I cannot) and I just rely on the current virtual to physical mapping to jump to the start address to execute the second kernel.
