From 2c43aced9be353f8428678a75495ca9d631dc927 Mon Sep 17 00:00:00 2001 From: Shanker Donthineni Date: Fri, 31 Jul 2026 18:52:43 +0100 Subject: [PATCH] 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 Reviewed-by: Fenghua Yu Tested-by: Fenghua Yu Reviewed-by: Ben Horgan Signed-off-by: Ben Horgan Signed-off-by: Will Deacon --- drivers/resctrl/mpam_devices.c | 6 ++---- 1 file 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)