[PATCH 4/4] ARM: apply the l2x0 Errata 769419 at run time

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Mon, Jan 21, 2013 at 06:47:12PM +0530, srinidhi kasagar wrote:
> Signed-off-by: srinidhi kasagar <srinidhi.kasagar@stericsson.com>
> ---
>  arch/arm/kernel/process.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index c6dec5f..c94d84f 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -39,6 +39,7 @@
>  #include <asm/thread_notify.h>
>  #include <asm/stacktrace.h>
>  #include <asm/mach/time.h>
> +#include <asm/hardware/cache-l2x0.h>
>  
>  #ifdef CONFIG_CC_STACKPROTECTOR
>  #include <linux/stackprotector.h>
> @@ -201,9 +202,11 @@ void cpu_idle(void)
>  			 * to ensure we don't miss a wakeup call.
>  			 */
>  			local_irq_disable();
> -#ifdef CONFIG_PL310_ERRATA_769419
> -			wmb();
> -#endif
> +
> +			/* Check for PL310 ERRATA 769419 */
> +			if (l2x0_get_rtl_release() == L2X0_CACHE_ID_RTL_R3P0)
> +				wmb();

You have to be joking if you think that is suitable... two reasons:

1. It's a horrid layering violation.
2. l2x0_get_rtl_release() unconditionally reads from a register in the L2
   controller.  What if you don't have a L2 controller?

Is it really worth this hastle, or would it just be better to keep the
ifdef there, using the configuration symbol as a way to indicate whether
we want this work-around included in the kernel, and always have the
wmb() there if the symbol is enabled?