Invalidate Data Cache from User Space

Invalidate Data Cache from User Space

[Jonathan Haws]

All,

I have a routine to invalidate the data cache from user space (since I do n=
ot believe there is a standard routine I can use outside of kernel space??)=
.

Here is the code:

	.text;
	.globl cacheInvalidate405;
cacheInvalidate405:

      /*
       *   r3 =3D Data cache
       *   r4 =3D address
       *   r5 =3D number of bytes
       */

        cmpwi   r5,0                /* make sure number of bytes is > 0 */
        beq     invalDone
        add     r6,r4,r5
        addi    r6,r6,31
        rlwinm  r6,r6,0,0,26        /* end addr to start of next cache line=
 */
        rlwinm  r7,r4,0,0,26        /* start address back to start of line =
 */
        sub     r6,r6,r7
        srawi   r6,r6,5             /* divide by 32 to get number of lines =
 */
        mtctr   r6
invalLoop:
        dcbi    r0,r4			/* THIS INSTRUCTION FAILS! */
        addi    r4,r4,32
        bdnz    invalLoop
        sync
invalDone:
        blr
.size	cacheInvalidate405, . - cacheInvalidate405

What is happening is the dcbi instruction will fail.  I get an Illegal Inst=
ruction message on the console and my program exits.

Is there a reason I cannot call dbci from a user space application, or is t=
here something wrong in my code?  Even better, is there a working and teste=
d function that I can call from user space to invalidate a portion of the d=
ata cache?

Thanks!

Jonathan

Re: Invalidate Data Cache from User Space

[Josh Boyer]

On Mon, Nov 09, 2009 at 11:10:42AM -0700, Jonathan Haws wrote:
>All,
>What is happening is the dcbi instruction will fail.  I get an Illegal Instruction message on the console and my program exits.
>
>Is there a reason I cannot call dbci from a user space application, or is there something wrong in my code?  Even better, is there a working and tested function that I can call from user space to invalidate a portion of the data cache?

dcbi is a priviledged instruction on 4xx.  You can only execute it from
supervisor mode (kernel).

josh