linux-kernel - Re: [PATCH 2/2] ARM: at91: setup outer cache .write

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Message-ID: <7f89d904-75d8-9dff-2d11-7511867de2d8@microchip.com>
Date:   Mon, 4 Jul 2022 06:39:11 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <clement.leger@...tlin.com>, <linux@...linux.org.uk>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/2] ARM: at91: setup outer cache .write_sec() callback if
 needed

On 06.06.2022 17:57, Clément Léger wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> When running under OP-TEE, the L2 cache is configured by OP-TEE and the
> sam platform code does not allow any modification yet. Setup a dummy
> .write_sec() callback to avoid triggering exceptions when Linux tries
> to modify the L2 cache configuration.
> 
> Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> ---
>  arch/arm/mach-at91/sama5.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/arm/mach-at91/sama5.c b/arch/arm/mach-at91/sama5.c
> index de5dd28b392e..d1a9e940a785 100644
> --- a/arch/arm/mach-at91/sama5.c
> +++ b/arch/arm/mach-at91/sama5.c
> @@ -9,13 +9,27 @@
>  #include <linux/of.h>
>  #include <linux/of_platform.h>
> 
> +#include <asm/hardware/cache-l2x0.h>
>  #include <asm/mach/arch.h>
>  #include <asm/mach/map.h>
> +#include <asm/outercache.h>
>  #include <asm/system_misc.h>
> 
>  #include "generic.h"
>  #include "sam_secure.h"
> 
> +static void sama5_l2c310_write_sec(unsigned long val, unsigned reg)
> +{
> +       /* OP-TEE configures the L2 cache and does not allow modifying it yet */
> +}
> +
> +static void __init sama5_secure_cache_init(void)
> +{
> +       sam_secure_init();

With this, could the sam_secure_init() in sama5d2_init() (not listed in
this diff) be removed?

> +       if (sam_linux_is_in_normal_world())
> +               outer_cache.write_sec = sama5_l2c310_write_sec;
> +}
> +
>  static void __init sama5_dt_device_init(void)
>  {
>         of_platform_default_populate(NULL, NULL, NULL);
> @@ -30,6 +44,7 @@ static const char *const sama5_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sama5_dt, "Atmel SAMA5")
>         /* Maintainer: Atmel */
>         .init_machine   = sama5_dt_device_init,
> +       .init_early     = sama5_secure_cache_init,

This is for the generic "atmel,sama5" which can apply also to sama5d3 or
sama5d4. I know this is harmless for functionality (except maybe when optee
is in DT) but do we want it here?

>         .dt_compat      = sama5_dt_board_compat,
>  MACHINE_END
> 
> @@ -41,6 +56,7 @@ static const char *const sama5_alt_dt_board_compat[] __initconst = {
>  DT_MACHINE_START(sama5_alt_dt, "Atmel SAMA5")
>         /* Maintainer: Atmel */
>         .init_machine   = sama5_dt_device_init,
> +       .init_early     = sama5_secure_cache_init,

Same here except it applies to sama5d4 only.

>         .dt_compat      = sama5_alt_dt_board_compat,
>         .l2c_aux_mask   = ~0UL,
>  MACHINE_END
> @@ -60,6 +76,7 @@ static const char *const sama5d2_compat[] __initconst = {
>  DT_MACHINE_START(sama5d2, "Atmel SAMA5")
>         /* Maintainer: Atmel */
>         .init_machine   = sama5d2_init,
> +       .init_early     = sama5_secure_cache_init,
>         .dt_compat      = sama5d2_compat,
>         .l2c_aux_mask   = ~0UL,
>  MACHINE_END
> --
> 2.36.1
>