Re: [microblaze-uclinux] PVR

[jack-uclinux@xxxxxxxxxxxxx]

On Tue, May 08, 2007 at 03:08:33PM +0200, Michal Simek wrote:
> Hi,
> 
> I tried to add Processor Version Register to U-BOOT but I hit againts a 
> small problem.
> I don't know how to write asembler instruction for PVR.

I worked around this problem by writing the MTS instruction in machine 
code. The machine code for copying special purpose register X into 
register r3, "mts r3, X", is ( 0x94608000 | X ). Include this in
inline assembly using .long.

Here is a sample C function that reads the value of an arbitrary SPR. 
It is more complex than it would need to be in order to read a
specific SPR, because it uses self-modifying code to generate the
MTS instruction with and must therefore disable the cache as it runs. 
Shame that Xilinx didn't allow the SPR number to be specified using 
a register.

    unsigned Get_SPR ( unsigned number )
    {   
        unsigned v = ( number ) & 0x3fff ;
        unsigned out = 0 ;
        
        asm volatile (
            "msrclr r31, 0xa2\n" /* caches, interrupts disabled (if used) */
            "addik  r3, r0, 0x94608000\n"
            "or     r3, r3, %1\n" 
            "swi    r3, r0, 0f\n" /* do modification */
            "or     r3, r0, r0\n" 
            "or     r3, r0, r0\n" /* NOPs for fetch buffer and pipeline */
            "or     r3, r0, r0\n"
            "or     r3, r0, r0\n"
            "or     r3, r0, r0\n"
            "or     r3, r0, r0\n"
            "0:\n"
            ".long 0xffffffff\n" /* Code that gets modified */
            "addk %0, r3, r0\n"
            "mts    rmsr, r31\n" /* MSR setting restored */
            : "=r"(out) : "r"(v) : "r3", "r31" ) ;
        return out ;
    }

Use Get_SPR ( 0x2000 ) to read PVR0.




-- 
Jack Whitham
jack@xxxxxxxxxxxxx

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