Re: [PATCH 3/5] MIPS: OCTEON: read the L2 crippled fuses from MIO_FUS_DAT3 on OCTEON II

[Thomas Bogendoerfer <tsbogend@alpha.franken.de>]

On Tue, Sep 15, 2026 at 07:12:46AM +0000, Orgad Shaneh wrote:
> prom_init() decides whether to lock lines into the L2 by reading
> L2D_FUS3, a CN3XXX/CN5XXX register. On OCTEON II the fuses that cripple
> the L2 are MIO_FUS_DAT3[l2c_crip] - which is what cvmx_l2c_get_num_assoc()
> already reads for those parts - so the test looks at an address that is
> not a register on the chip and gets a meaningless answer: it can skip
> L2 locking on a healthy cache, or lock into a reduced one.
> 
> Pick the register by family in a small helper.
> 
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Orgad Shaneh <orgads@gmail.com>
> ---
> diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
> --- a/arch/mips/cavium-octeon/setup.c
> +++ b/arch/mips/cavium-octeon/setup.c
> @@ -653,6 +653,24 @@ void octeon_user_io_init(void)
>  	write_c0_derraddr1(0);
>  }
>  
> +#ifdef CONFIG_CAVIUM_OCTEON_LOCK_L2
> +static bool __init octeon_l2_is_crippled(void)
> +{
> +	/*
> +	 * L2D_FUS3 exists on CN3XXX/CN5XXX only. On OCTEON II the
> +	 * crippled-L2 fuses live in MIO_FUS_DAT3[l2c_crip].
> +	 */
> +	if (OCTEON_IS_MODEL(OCTEON_CN6XXX)) {
> +		union cvmx_mio_fus_dat3 fus_dat3;
> +
> +		fus_dat3.u64 = cvmx_read_csr(CVMX_MIO_FUS_DAT3);
> +		return fus_dat3.s.l2c_crip != 0;
> +	}
> +
> +	return cvmx_read_csr(CVMX_L2D_FUS3) & (3ull << 34);
> +}
> +#endif
> +
>  /**
>   * prom_init - Early entry point for arch setup
>   */
> @@ -801,7 +819,7 @@ void __init prom_init(void)
>  	}
>  
>  #ifdef CONFIG_CAVIUM_OCTEON_LOCK_L2
> -	if (cvmx_read_csr(CVMX_L2D_FUS3) & (3ull << 34)) {
> +	if (octeon_l2_is_crippled()) {
>  		pr_info("Skipping L2 locking due to reduced L2 cache size\n");
>  	} else {
>  		uint32_t __maybe_unused ebase = read_c0_ebase() & 0x3ffff000;
> -- 
> 2.47.0

applied to mips-next

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]