From: Shanker Donthineni <redacted>

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.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Co-developed-by: Shanker Donthineni <redacted>
Signed-off-by: Shanker Donthineni <redacted>
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.
---
  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 37bd8efc6ecf..5f741df9abcc 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 */

@@ -1993,6 +2020,7 @@ 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)

@@ -2112,6 +2140,7 @@ 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)

@@ -2125,6 +2154,9 @@ __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 69cb75616561..d60a3caf6f6e 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;