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The >>> purpose of the minimum control is to give priority to tasks that are below >>> their minimum value. Resctrl only provides one value for the bandwidth >>> configuration, which is used for the maximum. >>> >>> >>> Hence, I'll drop this patch, and update the mbw_min default to be 0xFFFF >>> and for the value not to change even if mbw_max changes. I think this >>> leaves us in the best position going forward without any heuristics that >>> may come back to bite us later when proper support for a schema >>> supporting mbw_min is added to resctrl. Background: I previouslyshared original fix(seecodesnippet below) with James Morse ~2 years ago to address the errata, which explicitly recommends usinga 5% gap for mitigation of the Hardware issue (the problem described in commit text of T241-MPAM-4) For some reason theoriginalimplementationwas splitinto two patches:   - Generic change applicable toall chips   - Specific fixfor Graceerrata T241-MPAM-4 Issue: Dropping this patch impacts[PATCH v3 45/47] forthe errata fix. If removalis necessary, please mergethis changeinto the T241-MPAM-4-specific patch. --- a/drivers/platform/mpam/mpam_devices.c +++ b/drivers/platform/mpam/mpam_devices.c @@ -1190,8 +1190,12 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid, rprops->mbw_pbm_bits);          } -       if (mpam_has_feature(mpam_feat_mbw_min, rprops)) -               mpam_write_partsel_reg(msc, MBW_MIN, 0); +       if (mpam_has_feature(mpam_feat_mbw_min, rprops)) { +               if (mpam_has_feature(mpam_feat_mbw_max, cfg)) +                       mpam_write_partsel_reg(msc, MBW_MIN, cfg->mbw_min); +               else +                       mpam_write_partsel_reg(msc, MBW_MIN, 0); +       }         if (mpam_has_feature(mpam_feat_mbw_max, rprops)) {                 if (mpam_has_feature(mpam_feat_mbw_max, cfg)) @@ -2332,6 +2336,31 @@ static int __write_config(void *arg)          return 0;   } +static void mpam_extend_config(struct mpam_class *class, struct mpam_config *cfg) +{ +       struct mpam_props *cprops = &class->props; +       u32 min, delta; + +       /* +        * MAX and MIN should be set together. If only one is provided, +        * generate a configuration for the other. If only one control +        * type is supported, the other value will be ignored. +        * +        * Resctrl can only configure the MAX. +        * +        * Parts affected by Nvidia's T241-MPAM-4 depend on this occurring, +        * and recommend a 5% difference. +        */ +       if (mpam_has_feature(mpam_feat_mbw_max, cfg) && +           !mpam_has_feature(mpam_feat_mbw_min, cfg)){ +               delta = ((5 * MPAMCFG_MBW_MAX_MAX) / 100) - 1; +               min = max_t(s32, cfg->mbw_max - delta, BIT(cprops->bwa_wd)); + +               cfg->mbw_min = max_t(s32, cfg->mbw_max - delta, BIT(16 - cprops->bwa_wd)); +               mpam_set_feature(mpam_feat_mbw_min, cfg); +       } +} Shanker