privilege mode access to coprocessor register

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1

Hello,

I want the privilege and user mode access to the coprocessor register
C0, C1

I tried to write following for the c1 and c0 coprocessor

mrc p15, 0, r0, c1, c0, 2 @ read the coprocessor access control reg
    @@ write '1111' to bits 3,2,1,0 - which should enable user- and
    @@ privilege- mode access to the c1, c0 coprocessor
    orr r0, r0, #0x000f @
    mcr p15, 0, r0, c1, c0, 2 @ write back

With this much change, I can build the kernel without any error but
when I use the instruction "MRC p15. 0, r0, c1, c0, 1" in my code it
gives "illegal instruction error with this new uImage. so any one
reason?

Thanks,
Seema

2

Where do you write this code .? . Did you write your own kernel
module / a driver linked with kernel?

check the other MRC instruction being used in the arch specific .s
files for ARM .

Please check with the ARM documentation as well for the mnemonic
syntax.

~D

3

I wrote this code in the head.S file near arch/arm/boot/compressed/
head.S in line 520.

call_kernel: bl cache_clean_flush
                    bl cache_off

    mrc p15, 0, r0, c1, c0, 2 @ read the coprocessor access control
reg
    @@ write '1111' to bits 3,2,1,0 - which should enable user- and
    @@ privilege- mode access to the c1, c0 coprocessor
    orr r0, r0, #0x0f
    mcr p15, 0, r0, c1, c0, 2 @ write back

    mrc p15, 0, r0, c9, c14, 0 @ HGC: read the register...

    orr r0, #0x1
    mcr p15, 0, r0, c9, c14, 0 @ write back

        mov r0, #0 @ must be zero
        mov r1, r7 @ restore architecture number
        mov r2, r8 @ restore atags pointer
        mov pc, r4 @ call kernel
   @@ ....

Do any one know some other method?