On Mon, Mar 18, 2019 at 09:30:53AM +0100, Linus Walleij wrote:
> This adds support for setting the flag bit "write allocate
> override" to the L210 variant.
>
> The "write allocate override" bit is used on the Nomadik STn8815
> and is necessary to properly make use of the L210 cache on that
> machine without sporadic crashes.
>
> After this the platform can boot and run without any out-of-tree
> patches.
This is not something that should be done by the kernel but by the
firmware - needing this bit set is a basic requirement of having
the caches enabled, and if (eg) the boot loader enables the caches
it too will suffer this problem.
>
> Cc: devicetree@xxxxxxxxxxxxxxx
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/arm/l2c2x0.yaml | 5 +++++
> arch/arm/mm/cache-l2x0.c | 8 ++++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/arm/l2c2x0.yaml b/Documentation/devicetree/bindings/arm/l2c2x0.yaml
> index bfc5c185561c..4cffcda3e2b7 100644
> --- a/Documentation/devicetree/bindings/arm/l2c2x0.yaml
> +++ b/Documentation/devicetree/bindings/arm/l2c2x0.yaml
> @@ -168,6 +168,11 @@ properties:
> be specified to indicate that such transforms are precluded.
> type: boolean
>
> + arm,write-allocate-override:
> + description: On L210 only, normally the L210 will use HPROT attributes,
> + setting this bit overrides that behaviour and cause the cache to make all
> + write-through and write-back accesses into read-write-allocate accesses.
> +
> arm,parity-enable:
> description: enable parity checking on the L2 cache (L220 or PL310).
> type: boolean
> diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
> index 808efbb89b88..5cbdb9c18884 100644
> --- a/arch/arm/mm/cache-l2x0.c
> +++ b/arch/arm/mm/cache-l2x0.c
> @@ -1078,6 +1078,14 @@ static void __init l2x0_of_parse(const struct device_node *np,
> val |= L2C_AUX_CTRL_SHARED_OVERRIDE;
> }
>
> + /* L210-specific aux control flag */
> + if (of_device_is_compatible(np, "arm,l210-cache")) {
> + if (of_property_read_bool(np, "arm,write-allocate-override")) {
> + mask &= ~L210_AUX_CTRL_WA_OVERRIDE;
> + val |= L210_AUX_CTRL_WA_OVERRIDE;
> + }
> + }
> +
> ret = l2x0_cache_size_of_parse(np, aux_val, aux_mask, &assoc, SZ_256K);
> if (ret)
> return;
> --
> 2.20.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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