[PATCH] l2c: warn about misconfigured PL310 shared-override

[PATCH] l2c: warn about misconfigured PL310 shared-override

[Lucas Stach]

If the shared override enable bit in the PL310 aux ctrl register is
not set the L2 cache controller will render the system non-compliant
to the rules regarding mismatched memory aliases as specified in the
ARMv7 ARM RevC.

As this may lead to subtle corruptions when reading from a bufferable
alias, make sure to warn about this in the kernel log.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 arch/arm/mm/cache-l2x0.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
index c61996c256cc..d2690f0d3cd0 100644
--- a/arch/arm/mm/cache-l2x0.c
+++ b/arch/arm/mm/cache-l2x0.c
@@ -815,6 +815,11 @@ static int __init __l2c_init(const struct l2c_init_data *data,
 		pr_warn("L2C: DT/platform modifies aux control register: 0x%08x -> 0x%08x\n",
 		        old_aux, aux);
 
+	if (((cache_id & L2X0_CACHE_ID_PART_MASK) == L2X0_CACHE_ID_PART_L310) &&
+	    !(aux & L2C_AUX_CTRL_SHARED_OVERRIDE))
+		pr_warn("L2C-310 shared attribute override enable not set, "
+			"system is non-compliant to ARM specified memory aliasing rules\n");
+
 	/* Determine the number of ways */
 	switch (cache_id & L2X0_CACHE_ID_PART_MASK) {
 	case L2X0_CACHE_ID_PART_L310:
-- 
2.8.1

[PATCH] l2c: warn about misconfigured PL310 shared-override

[Fabio Estevam]

Hi Lucas,

On Tue, May 31, 2016 at 11:43 AM, Lucas Stach <l.stach@pengutronix.de> wrote:

> diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
> index c61996c256cc..d2690f0d3cd0 100644
> --- a/arch/arm/mm/cache-l2x0.c
> +++ b/arch/arm/mm/cache-l2x0.c
> @@ -815,6 +815,11 @@ static int __init __l2c_init(const struct l2c_init_data *data,
>                 pr_warn("L2C: DT/platform modifies aux control register: 0x%08x -> 0x%08x\n",
>                         old_aux, aux);
>
> +       if (((cache_id & L2X0_CACHE_ID_PART_MASK) == L2X0_CACHE_ID_PART_L310) &&
> +           !(aux & L2C_AUX_CTRL_SHARED_OVERRIDE))
> +               pr_warn("L2C-310 shared attribute override enable not set, "
> +                       "system is non-compliant to ARM specified memory aliasing rules\n");
> +

Should something like "Make sure to set this bit in the bootloader" be
displayed? At least this would give some hint as to where the problem
needs to be fixed.