[PATCH v5 36/41] arm_mpam: Add quirk framework

Ben Horgan
2026-02-24T18:00:54Z

From: Shanker Donthineni <sdonthineni@nvidia.com>

The MPAM specification includes the MPAMF_IIDR, which serves to uniquely
identify the MSC implementation through a combination of implementer
details, product ID, variant, and revision. Certain hardware issues/errata
can be resolved using software workarounds.

Introduce a quirk framework to allow workarounds to be enabled based on the
MPAMF_IIDR value.

Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Co-developed-by: James Morse <james.morse@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes by James:
Stash the IIDR so this doesn't need an IPI, enable quirks only
once, move the description to the callback so it can be pr_once()d, add an
enum of workarounds for popular errata. Add macros for making lists of
product/revision/vendor half readable

Changes since rfc:
remove trailing commas in last element of enums
Make mpam_enable_quirks() in charge of mpam_set_quirk() even if there
is an enable.

Changes since v3:
Brackets in macro
---
drivers/resctrl/mpam_devices.c | 32 ++++++++++++++++++++++++++++++++
drivers/resctrl/mpam_internal.h | 25 +++++++++++++++++++++++++
2 files changed, 57 insertions(+)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 528936ececd9..382dc5c9b885 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -630,6 +630,30 @@ static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc,
return ERR_PTR(-ENOENT);
}

+static const struct mpam_quirk mpam_quirks[] = {
+ { NULL } /* Sentinel */
+};
+
+static void mpam_enable_quirks(struct mpam_msc *msc)
+{
+ const struct mpam_quirk *quirk;
+
+ for (quirk = &mpam_quirks[0]; quirk->iidr_mask; quirk++) {
+ int err = 0;
+
+ if (quirk->iidr != (msc->iidr & quirk->iidr_mask))
+ continue;
+
+ if (quirk->init)
+ err = quirk->init(msc, quirk);
+
+ if (err)
+ continue;
+
+ mpam_set_quirk(quirk->workaround, msc);
+ }
+}
+
/*
* IHI009A.a has this nugget: "If a monitor does not support automatic behaviour
* of NRDY, software can use this bit for any purpose" - so hardware might not
@@ -864,8 +888,11 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
/* Grab an IDR value to find out how many RIS there are */
mutex_lock(&msc->part_sel_lock);
idr = mpam_msc_read_idr(msc);
+ msc->iidr = mpam_read_partsel_reg(msc, IIDR);
mutex_unlock(&msc->part_sel_lock);

+ mpam_enable_quirks(msc);
+
msc->ris_max = FIELD_GET(MPAMF_IDR_RIS_MAX, idr);

/* Use these values so partid/pmg always starts with a valid value */
@@ -1988,6 +2015,7 @@ static bool mpam_has_cmax_wd_feature(struct mpam_props *props)
* resulting safe value must be compatible with both. When merging values in
* the tree, all the aliasing resources must be handled first.
* On mismatch, parent is modified.
+ * Quirks on an MSC will apply to all MSC in that class.
*/
static void __props_mismatch(struct mpam_props *parent,
struct mpam_props *child, bool alias)
@@ -2107,6 +2135,7 @@ static void __props_mismatch(struct mpam_props *parent,
* nobble the class feature, as we can't configure all the resources.
* e.g. The L3 cache is composed of two resources with 13 and 17 portion
* bitmaps respectively.
+ * Quirks on an MSC will apply to all MSC in that class.
*/
static void
__class_props_mismatch(struct mpam_class *class, struct mpam_vmsc *vmsc)
@@ -2120,6 +2149,9 @@ __class_props_mismatch(struct mpam_class *class, struct mpam_vmsc *vmsc)
dev_dbg(dev, "Merging features for class:0x%lx &= vmsc:0x%lx\n",
(long)cprops->features, (long)vprops->features);

+ /* Merge quirks */
+ class->quirks |= vmsc->msc->quirks;
+
/* Take the safe value for any common features */
__props_mismatch(cprops, vprops, false);
}
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index a79c7670f7ae..60e445e94ee6 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -85,6 +85,8 @@ struct mpam_msc {
u8 pmg_max;
unsigned long ris_idxs;
u32 ris_max;
+ u32 iidr;
+ u16 quirks;

/*
* error_irq_lock is taken when registering/unregistering the error
@@ -216,6 +218,28 @@ struct mpam_props {
#define mpam_set_feature(_feat, x) __set_bit(_feat, (x)->features)
#define mpam_clear_feature(_feat, x) __clear_bit(_feat, (x)->features)

+/* Workaround bits for msc->quirks */
+enum mpam_device_quirks {
+ MPAM_QUIRK_LAST
+};
+
+#define mpam_has_quirk(_quirk, x) ((1 << (_quirk) & (x)->quirks))
+#define mpam_set_quirk(_quirk, x) ((x)->quirks |= (1 << (_quirk)))
+
+struct mpam_quirk {
+ int (*init)(struct mpam_msc *msc, const struct mpam_quirk *quirk);
+
+ u32 iidr;
+ u32 iidr_mask;
+
+ enum mpam_device_quirks workaround;
+};
+
+#define MPAM_IIDR_MATCH_ONE (FIELD_PREP_CONST(MPAMF_IIDR_PRODUCTID, 0xfff) | \
+ FIELD_PREP_CONST(MPAMF_IIDR_VARIANT, 0xf) | \
+ FIELD_PREP_CONST(MPAMF_IIDR_REVISION, 0xf) | \
+ FIELD_PREP_CONST(MPAMF_IIDR_IMPLEMENTER, 0xfff))
+
/* The values for MSMON_CFG_MBWU_FLT.RWBW */
enum mon_filter_options {
COUNT_BOTH = 0,
@@ -259,6 +283,7 @@ struct mpam_class {

struct mpam_props props;
u32 nrdy_usec;
+ u16 quirks;
u8 level;
enum mpam_class_types type;

--
2.43.0