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iommu/io-pgtable-arm-v7s: Clarify LVL_SHIFT/BITS macro

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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 clarify the two macro. No functional change.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-12-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Yong Wu 2021-01-11 19:18:52 +08:00 committed by Will Deacon
parent 40596d2f2b
commit 00ab6f2d61
1 changed files with 3 additions and 5 deletions
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8
drivers/iommu/io-pgtable-arm-v7s.c
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@ -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))