Re: [PATCH v2] Virtual memory size detection for 64 bit MIPS CPUs

[David Daney <ddaney@caviumnetworks.com>]

Guenter Roeck wrote:
[...]
>  
> +static inline void cpu_set_vmbits(struct cpuinfo_mips *c)
> +{
> +       if (cpu_has_64bits) {
> +               unsigned long zbits;
> +
> +               asm volatile(".set mips64\n"
> +                            "and %0, 0\n"
> +                            "dsubu %0, 1\n"
> +                            "dmtc0 %0, $10, 0\n"
> +                            "dmfc0 %0, $10, 0\n"
> +                            "dsll %0, %0, 2\n"
> +                            "dsra %0, %0, 2\n"
> +                            "dclz %0, %0\n"
> +                            ".set mips0\n"
> +                            : "=r" (zbits));
> +               c->vmbits = 64 - zbits;
> +       } else
> +               c->vmbits = 32;
> +}
> +
It should be possible to express this in 'pure' C using 
read_c0_entryhi()/write_c0_entryhi(), also you need to be sure you are 
not writing 1s to any reserved bits of the register.

David Daney