Re: [PATCH v4 09/24] iommu/io-pgtable-arm-v7s: Clear LVL_SHIFT/BITS macro instead of the formula

Robin Murphy
2020-11-26T16:06:43Z

On 2020-11-11 12:38, Yong Wu wrote:
> The current _ARM_V7S_LVL_BITS/ARM_V7S_LVL_SHIFT use a formula to calculate
> the corresponding value for level1 and level2 to pretend the code sane.
> Actually their level1 and level2 values are different from each other.
> This patch only clear the two macro. No functional change.

Grammar nit: to "clear" the macro sounds like you're making it empty or
removing it entirely; I think you mean to say "clarify" here. English is
the worst language sometimes... :)

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Suggested-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> drivers/iommu/io-pgtable-arm-v7s.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index 4d0aa079470f..58cc201c10a3 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -44,13 +44,11 @@
>
> /*
> * We have 32 bits total; 12 bits resolved at level 1, 8 bits at level 2,
> - * and 12 bits in a page. With some carefully-chosen coefficients we can
> - * hide the ugly inconsistencies behind these macros and at least let the
> - * rest of the code pretend to be somewhat sane.
> + * and 12 bits in a page.
> */
> #define ARM_V7S_ADDR_BITS 32
> -#define _ARM_V7S_LVL_BITS(lvl) (16 - (lvl) * 4)
> -#define ARM_V7S_LVL_SHIFT(lvl) (ARM_V7S_ADDR_BITS - (4 + 8 * (lvl)))
> +#define _ARM_V7S_LVL_BITS(lvl) ((lvl) == 1 ? 12 : 8)
> +#define ARM_V7S_LVL_SHIFT(lvl) ((lvl) == 1 ? 20 : 12)
> #define ARM_V7S_TABLE_SHIFT 10
>
> #define ARM_V7S_PTES_PER_LVL(lvl) (1 << _ARM_V7S_LVL_BITS(lvl))
>