arm_mpam: Pretend that NRDY is always hardware managed

Rule ZTXDS of the MPAM specification, IHI009 version B.b, states: "If a
monitor does not support automatic updates of NRDY, software can use that
bit for any purpose."

As software is not reliably informed whether or not the monitor supports
automatic updates of NRDY always assume that hardware may manage NRDY but
don't rely on it. When NRDY is truly untouched by hardware then, as it is
written to 0 on configuration, it will always read 0.

At probe it's checked if MSMON_CSU.NRDY and MSMON_MBWU.NRDY are hardware
managed but not MSMON_MBWU_L.NDRY. Specialize the checking for hardware
managed NRDY to CSU counters as this is the only case where hardware
management makes sense. Continue to inform the user if MSMON_CSU.NRDY
appears to be hardware managed but the firmware doesn't provide the
associated time limit for the automatic clearing of NRDY. Remove the NRDY
feature flags as they are now unused.

Fixes: 8c90dc68a5de ("arm_mpam: Probe the hardware features resctrl supports")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 817cb10a8e795f97bab1b8934c2099b762e48d43..58e0c8970e8cf4e5eb60aaa15bec8aeade7d6e5c 100644 (file)
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -728,7 +728,7 @@ static void mpam_enable_quirks(struct mpam_msc *msc)
  * Try and see what values stick in this bit. If we can write either value,
  * its probably not implemented by hardware.
  */
-static bool _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc_ris *ris, u32 mon_reg)
+static bool mpam_ris_hw_probe_csu_nrdy(struct mpam_msc_ris *ris)
 {
        u32 now;
        u32 mon_sel;
@@ -742,21 +742,18 @@ static bool _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc_ris *ris, u32 mon_reg)
                  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
        mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
 
-       _mpam_write_monsel_reg(msc, mon_reg, MSMON___NRDY);
-       now = _mpam_read_monsel_reg(msc, mon_reg);
+       _mpam_write_monsel_reg(msc, MSMON_CSU, MSMON___NRDY);
+       now = _mpam_read_monsel_reg(msc, MSMON_CSU);
        can_set = now & MSMON___NRDY;
 
-       _mpam_write_monsel_reg(msc, mon_reg, 0);
-       now = _mpam_read_monsel_reg(msc, mon_reg);
+       _mpam_write_monsel_reg(msc, MSMON_CSU, 0);
+       now = _mpam_read_monsel_reg(msc, MSMON_CSU);
        can_clear = !(now & MSMON___NRDY);
        mpam_mon_sel_unlock(msc);
 
        return (!can_set || !can_clear);
 }
 
-#define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg)                      \
-       _mpam_ris_hw_probe_hw_nrdy(_ris, MSMON_##_mon_reg)
-
 static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
 {
        int err;
@@ -873,20 +870,18 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
                                        mpam_set_feature(mpam_feat_msmon_csu_xcl, props);
 
                                /* Is NRDY hardware managed? */
-                               hw_managed = mpam_ris_hw_probe_hw_nrdy(ris, CSU);
-                               if (hw_managed)
-                                       mpam_set_feature(mpam_feat_msmon_csu_hw_nrdy, props);
-                       }
+                               hw_managed = mpam_ris_hw_probe_csu_nrdy(ris);
 
-                       /*
-                        * Accept the missing firmware property if NRDY appears
-                        * un-implemented.
-                        */
-                       if (err && mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, props))
-                               dev_err_once(dev, "Counters are not usable because not-ready timeout was not provided by firmware.");
+                               /*
+                                * Accept the missing firmware property if NRDY appears
+                                * un-implemented.
+                                */
+                               if (err && hw_managed)
+                                       dev_err_once(dev, "Counters are not usable because not-ready timeout was not provided by firmware.");
+                       }
                }
                if (FIELD_GET(MPAMF_MSMON_IDR_MSMON_MBWU, msmon_features)) {
-                       bool has_long, hw_managed;
+                       bool has_long;
                        u32 mbwumon_idr = mpam_read_partsel_reg(msc, MBWUMON_IDR);
 
                        props->num_mbwu_mon = FIELD_GET(MPAMF_MBWUMON_IDR_NUM_MON, mbwumon_idr);
@@ -905,16 +900,6 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
                                } else {
                                        mpam_set_feature(mpam_feat_msmon_mbwu_31counter, props);
                                }
-
-                               /* Is NRDY hardware managed? */
-                               hw_managed = mpam_ris_hw_probe_hw_nrdy(ris, MBWU);
-                               if (hw_managed)
-                                       mpam_set_feature(mpam_feat_msmon_mbwu_hw_nrdy, props);
-
-                               /*
-                                * Don't warn about any missing firmware property for
-                                * MBWU NRDY - it doesn't make any sense!
-                                */
                        }
                }
        }
@@ -1197,7 +1182,6 @@ static void __ris_msmon_read(void *arg)
        bool reset_on_next_read = false;
        struct mpam_msc_ris *ris = m->ris;
        struct msmon_mbwu_state *mbwu_state;
-       struct mpam_props *rprops = &ris->props;
        struct mpam_msc *msc = m->ris->vmsc->msc;
        u32 mon_sel, ctl_val, flt_val, cur_ctl, cur_flt;
 
@@ -1253,8 +1237,7 @@ static void __ris_msmon_read(void *arg)
        switch (m->type) {
        case mpam_feat_msmon_csu:
                now = mpam_read_monsel_reg(msc, CSU);
-               if (mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, rprops))
-                       nrdy = now & MSMON___NRDY;
+               nrdy = now & MSMON___NRDY;
                now = FIELD_GET(MSMON___VALUE, now);
 
                if (mpam_has_quirk(IGNORE_CSU_NRDY, msc) && m->waited_timeout)
@@ -1266,8 +1249,7 @@ static void __ris_msmon_read(void *arg)
        case mpam_feat_msmon_mbwu_63counter:
                if (m->type != mpam_feat_msmon_mbwu_31counter) {
                        now = mpam_msc_read_mbwu_l(msc);
-                       if (mpam_has_feature(mpam_feat_msmon_mbwu_hw_nrdy, rprops))
-                               nrdy = now & MSMON___L_NRDY;
+                       nrdy = now & MSMON___L_NRDY;
 
                        if (m->type == mpam_feat_msmon_mbwu_63counter)
                                now = FIELD_GET(MSMON___LWD_VALUE, now);
@@ -1275,8 +1257,7 @@ static void __ris_msmon_read(void *arg)
                                now = FIELD_GET(MSMON___L_VALUE, now);
                } else {
                        now = mpam_read_monsel_reg(msc, MBWU);
-                       if (mpam_has_feature(mpam_feat_msmon_mbwu_hw_nrdy, rprops))
-                               nrdy = now & MSMON___NRDY;
+                       nrdy = now & MSMON___NRDY;
                        now = FIELD_GET(MSMON___VALUE, now);
                }
 

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 1914aefdcba9efbed62b01d05ab88e47fd49c421..04d1a59f02afb4327f33925c8bd8e313a07d3cd2 100644 (file)
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -181,14 +181,12 @@ enum mpam_device_features {
        mpam_feat_msmon_csu,
        mpam_feat_msmon_csu_capture,
        mpam_feat_msmon_csu_xcl,
-       mpam_feat_msmon_csu_hw_nrdy,
        mpam_feat_msmon_mbwu,
        mpam_feat_msmon_mbwu_31counter,
        mpam_feat_msmon_mbwu_44counter,
        mpam_feat_msmon_mbwu_63counter,
        mpam_feat_msmon_mbwu_capture,
        mpam_feat_msmon_mbwu_rwbw,
-       mpam_feat_msmon_mbwu_hw_nrdy,
        mpam_feat_partid_nrw,
        MPAM_FEATURE_LAST
 };