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SubjectRe: [PATCH] arc: Flush and invalidate caches on start
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On 08/31/2017 07:22 AM, Alexey Brodkin wrote:
> This is useful to make sure no stale data exists in caches after bootloaders.
> The worst thing could be some lines of cache were locked in a bootloader
> for example during DDR recalibration and never unlocked. This may lead
> to really unpredictable issues later down the line.
>
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
> ---
> arch/arc/kernel/head.S | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
> index 8b90d25a15cc..04e28b664183 100644
> --- a/arch/arc/kernel/head.S
> +++ b/arch/arc/kernel/head.S
> @@ -34,6 +34,10 @@
> #endif
> sr r5, [ARC_REG_IC_CTRL]
>
> + ; Invalidate entire I$
> + mov r5, 1
> + sr r5, [ARC_REG_IC_IVIC]
> +
> 1:
> lr r5, [ARC_REG_DC_BCR]
> breq r5, 0, 1f ; D$ doesn't exist
> @@ -46,6 +50,18 @@
> #endif
> sr r5, [ARC_REG_DC_CTRL]
>
> + ; Flush entire D$
> + mov r5, 1
> + sr r5, [ARC_REG_DC_FLSH]
> + ; Wait for flush operation to complete
> +1:
> + lr r5, [ARC_REG_DC_CTRL]
> + bbit1 r5, DC_CTRL_FLUSH_STATUS, 1b
> +
> + ; Invalidate entire D$
> + mov r5, 1
> + sr r5, [ARC_REG_DC_IVDC]
> +

AFAIK uboot already flushes the caches before handing control over to kernel - so
why do we need it here.
If uboot is locking lines, it needs to fix that and not penalize the general case
with or w/o uboot !

-Vineet

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