Re: [PATCH] MIPS: reloc: make flush_cache_all() usable

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Antony,

On Fri, Jun 21, 2019 at 08:15:07AM +0300, Antony Pavlov wrote:
> flush_cache_all() uses 'struct cpuinfo_mips current_cpu_data' data fields.
> These data fields are initialized in r4k_cache_init().
> 
> However in the current implementation the r4k_cache_init() function
> is called __AFTER__ relocate_code().
> 
> Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
> ---
>  arch/mips/lib/reloc.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/mips/lib/reloc.c b/arch/mips/lib/reloc.c
> index 14ba6167dd..6f1cd6d82f 100644
> --- a/arch/mips/lib/reloc.c
> +++ b/arch/mips/lib/reloc.c
> @@ -37,6 +37,7 @@
>  #include <asm/mipsregs.h>
>  #include <asm/relocs.h>
>  #include <asm/sections.h>
> +#include <asm/cpu-features.h>
>  #include <linux/sizes.h>
>  #include <asm-generic/memory_layout.h>
>  
> @@ -157,6 +158,17 @@ void relocate_code(void *fdt, u32 fdt_size, u32 ram_size)
>  		apply_reloc(type, (void *)addr, off);
>  	}
>  
> +	/* clear the BSS first */
> +	memset(__bss_start, 0x00, bss_len);
> +
> +	cpu_probe();
> +
> +	if (cpu_has_4k_cache) {
> +		extern void r4k_cache_init(void);
> +
> +		r4k_cache_init();
> +	}
> +
>  	/* Ensure the icache is coherent */
>  	flush_cache_all();

Can we initialize one field in current_cpu_data to something nonzero so
that it goes out of the bss?

Another way would be to pass cpu_probe() a pointer to a struct
cpuinfo_mips allocated on the stack and then pass it to
flush_cache_all().

Clearing the bss twice doesn't look very nice.

Sascha

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