arm_mpam: Apply T241-MPAM-6 to 63-bit counters

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T241-MPAM-6 causes all MBWU counter formats to count 64-byte
requests instead of bytes. Commit dc48eb1ff2 excluded the 63-bit
MSMON_MBWU_LWD format while scaling the shorter counters. Systems
selecting the preferred 63-bit counter consequently report bandwidth
values that are 64 times too small.

Apply the scale to both the sampled value and overflow correction for
the 63-bit format. Unsigned arithmetic retains modulo-u64 behavior
when the scaled counter range exceeds u64.

Fixes: dc48eb1ff2 ("arm_mpam: Add workaround for T241-MPAM-6")
Link: https://lore.kernel.org/lkml/20240816131432.993859-1-sdonthineni@nvidia.com/
Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

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Shanker Donthineni 2026-07-31 18:52:43 +01:00 • committed by Will Deacon

parent 6b4ee75215

commit 2c43aced9b

1 changed files with 2 additions and 4 deletions

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drivers/resctrl/mpam_devices.c

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