Re: [PATCH] powerpc32: memcpy: only use dcbz once cache is enabled

From: Michal Sojka
Date: Mon Sep 07 2015 - 10:56:23 EST

On Mon, Sep 07 2015, Christophe Leroy wrote:
> memcpy() uses instruction dcbz to speed up copy by not wasting time
> loading cache line with data that will be overwritten.
> Some platform like mpc52xx do no have cache active at startup and
> can therefore not use memcpy(). Allthough no part of the code
> explicitly uses memcpy(), GCC makes calls to it.
> This patch modifies memcpy() such that at startup, the 'dcbz'
> instruction is replaced by 'dcbt' which is harmless if cache is not
> enabled, and which helps a bit (allthough not as much as dcbz) if
> cache is already enabled.
> Once the initial MMU is setup, in machine_init() we patch memcpy()
> by replacing the temporary 'dcbt' by 'dcbz'
> Reported-by: Michal Sojka <sojkam1@xxxxxxxxxxx>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
> @Michal, can you please test it ?

Yes, it works.

Tested-by: Michal Sojka <sojkam1@xxxxxxxxxxx>

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at