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| author | Shanker Donthineni <sdonthineni@nvidia.com> | 2026-07-31 18:52:43 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2026-08-02 09:33:43 +0000 |
| commit | 2c43aced9be353f8428678a75495ca9d631dc927 (patch) | |
| tree | 92b3abd04ec1bc699a0ca0b6e64ec4477de605af | |
| parent | 6b4ee75215c9dbcf6a0fd8cf7af2449906e2932c (diff) | |
| download | linux-next-2c43aced9be353f8428678a75495ca9d631dc927.tar.gz linux-next-2c43aced9be353f8428678a75495ca9d631dc927.zip | |
arm_mpam: Apply T241-MPAM-6 to 63-bit counters
T241-MPAM-6 causes all MBWU counter formats to count 64-byte
requests instead of bytes. Commit dc48eb1ff27c 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: dc48eb1ff27c ("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>
| -rw-r--r-- | drivers/resctrl/mpam_devices.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c index b69f99488111..53942b331269 100644 --- a/drivers/resctrl/mpam_devices.c +++ b/drivers/resctrl/mpam_devices.c @@ -1196,8 +1196,7 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type, { u64 overflow_val = __mpam_msmon_overflow_val(type); - if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc) && - type != mpam_feat_msmon_mbwu_63counter) + if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc)) overflow_val *= 64; return overflow_val; @@ -1293,8 +1292,7 @@ static void __ris_msmon_read(void *arg) now = FIELD_GET(MSMON___VALUE, now); } - if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc) && - m->type != mpam_feat_msmon_mbwu_63counter) + if (mpam_has_quirk(T241_MBW_COUNTER_SCALE_64, msc)) now *= 64; if (nrdy) |