why not put 64 bit value directly to register

["Bin Chen" <binary.chen@xxxxxxxxx>]

Hi,

This code is snip from u-boot, I don't know why the 32bit-64bit
conversion is needed, why not put val directly to register but do the
transform?

static void cvmx_write_cop0_entry_lo_0(uint64_t val)
{
    uint32_t val_low  = val & 0xffffffff;
    uint32_t val_high = val  >> 32;

    uint32_t tmp; /* temp register */

    asm volatile (
        "  .set
mips64                      
\n"
        "  .set
noreorder                   
\n"
        /* Standard twin 32 bit -> 64 bit construction */
        "  dsll  %[valh],
32                
\n"
        "  dla  
%[tmp],
0xffffffff          \n"
        "  and   %[vall], %[tmp], %[vall]    \n"
        "  daddu %[valh], %[valh], %[vall]   \n"
        /* Combined value is in valh */
        "  dmtc0
%[valh],$2,0               
\n"
        "  .set
reorder                     
\n"
         :[tmp] "=&r" (tmp) : [valh] "r" (val_high), [vall] "r" (val_low) );
}

Thanks.
B.C