arm_mpam: Quirk CMN-650's CSU NRDY behaviour

CMN-650 is afflicted with an erratum where the CSU NRDY bit never clears.
This tells us the monitor never finishes scanning the cache. The erratum
document says to wait the maximum time, then ignore the field.

Add a flag to indicate whether this is the final attempt to read the
counter, and when this quirk is applied, ignore the NRDY field.

This means accesses to this counter will always retry, even if the counter
was previously programmed to the same values.

The counter value is not expected to be stable, it drifts up and down with
each allocation and eviction. The CSU register provides the value for a
point in time.

Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com>
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Jesse Chick <jessechick@os.amperecomputing.com>
Reviewed-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Co-developed-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index 1aa3326bb32000888dac50bae904b62b2a0c656e..65ed6ea33751f961d0535e3bd97b6b30b2e962df 100644 (file)
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -214,6 +214,9 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | SI L1           | #4311569        | ARM64_ERRATUM_4311569       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | CMN-650         | #3642720        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
++----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_845719        |
 +----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_843419        |

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 1a92c8c42b59d1e9cd47f9fb2e8965446092b506..3e419e59a36f3588fbcc336aa65ca27905d6c35b 100644 (file)
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -691,6 +691,12 @@ static const struct mpam_quirk mpam_quirks[] = {
                .iidr_mask  = MPAM_IIDR_MATCH_ONE,
                .workaround = T241_MBW_COUNTER_SCALE_64,
        },
+       {
+       /* ARM CMN-650 CSU erratum 3642720 */
+       .iidr       = MPAM_IIDR_ARM_CMN_650,
+       .iidr_mask  = MPAM_IIDR_MATCH_ONE,
+       .workaround = IGNORE_CSU_NRDY,
+       },
        { NULL } /* Sentinel */
 };
 
@@ -1003,6 +1009,7 @@ struct mon_read {
        enum mpam_device_features       type;
        u64                             *val;
        int                             err;
+       bool                            waited_timeout;
 };
 
 static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris)
@@ -1249,6 +1256,10 @@ static void __ris_msmon_read(void *arg)
                if (mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, rprops))
                        nrdy = now & MSMON___NRDY;
                now = FIELD_GET(MSMON___VALUE, now);
+
+               if (mpam_has_quirk(IGNORE_CSU_NRDY, msc) && m->waited_timeout)
+                       nrdy = false;
+
                break;
        case mpam_feat_msmon_mbwu_31counter:
        case mpam_feat_msmon_mbwu_44counter:
@@ -1386,6 +1397,7 @@ int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
                        .ctx = ctx,
                        .type = type,
                        .val = val,
+                       .waited_timeout = true,
                };
                *val = 0;
 

diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 8fea28c5fb852b3958d88e392ea71aa1ba57b1fa..1914aefdcba9efbed62b01d05ab88e47fd49c421 100644 (file)
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -226,6 +226,7 @@ enum mpam_device_quirks {
        T241_SCRUB_SHADOW_REGS,
        T241_FORCE_MBW_MIN_TO_ONE,
        T241_MBW_COUNTER_SCALE_64,
+       IGNORE_CSU_NRDY,
        MPAM_QUIRK_LAST
 };
 
@@ -251,6 +252,11 @@ struct mpam_quirk {
                                 FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0)     | \
                                 FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0x36b))
 
+#define MPAM_IIDR_ARM_CMN_650  (FIELD_PREP_CONST(MPAMF_IIDR_PRODUCTID,   0)     | \
+                                FIELD_PREP_CONST(MPAMF_IIDR_VARIANT,     0)     | \
+                                FIELD_PREP_CONST(MPAMF_IIDR_REVISION,    0)     | \
+                                FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0x43b))
+
 /* The values for MSMON_CFG_MBWU_FLT.RWBW */
 enum mon_filter_options {
        COUNT_BOTH      = 0,