linux-kernel - [PATCH v2 02/17] coresight: trbe: Add infrastructure for Errata handling

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Date:   Tue, 21 Sep 2021 14:41:06 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, maz@...nel.org,
        catalin.marinas@....com, mark.rutland@....com, james.morse@....com,
        anshuman.khandual@....com, leo.yan@...aro.org,
        mike.leach@...aro.org, mathieu.poirier@...aro.org, will@...nel.org,
        lcherian@...vell.com, coresight@...ts.linaro.org,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v2 02/17] coresight: trbe: Add infrastructure for Errata handling

Add a minimal infrastructure to keep track of the errata
affecting the given TRBE instance. Given that we have
heterogeneous CPUs, we have to manage the list per-TRBE
instance to be able to apply the work around as needed.

We rely on the arm64 errata framework for the actual
description and the discovery of a given erratum, to
keep the Erratum work around at a central place and
benefit from the code and the advertisement from the
kernel. We use a local mapping of the erratum to
avoid bloating up the individual TRBE structures.
i.e, each arm64 TRBE erratum bit is assigned a new number
within the driver to track. Each trbe instance updates
the list of affected erratum at probe time on the CPU.
This makes sure that we can easily access the list of
errata on a given TRBE instance without much overhead.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Leo Yan <leo.yan@...aro.org>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
Changes since v1:
  - Flip the order of args for trbe_has_erratum()
  - Move erratum detection further down in the sequence
---
 drivers/hwtracing/coresight/coresight-trbe.c | 49 ++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index e3d73751d568..63f7edd5fd1f 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -16,6 +16,8 @@
 #define pr_fmt(fmt) DRVNAME ": " fmt
 
 #include <asm/barrier.h>
+#include <asm/cputype.h>
+
 #include "coresight-self-hosted-trace.h"
 #include "coresight-trbe.h"
 
@@ -65,6 +67,35 @@ struct trbe_buf {
 	struct trbe_cpudata *cpudata;
 };
 
+/*
+ * TRBE erratum list
+ *
+ * We rely on the corresponding cpucaps to be defined for a given
+ * TRBE erratum. We map the given cpucap into a TRBE internal number
+ * to make the tracking of the errata lean.
+ *
+ * This helps in :
+ *   - Not duplicating the detection logic
+ *   - Streamlined detection of erratum across the system
+ *
+ * Since the erratum work arounds could be applied individually
+ * per TRBE instance, we keep track of the list of errata that
+ * affects the given instance of the TRBE.
+ */
+#define TRBE_ERRATA_MAX			0
+
+static unsigned long trbe_errata_cpucaps[TRBE_ERRATA_MAX] = {
+};
+
+/*
+ * struct trbe_cpudata: TRBE instance specific data
+ * @trbe_flag		- TRBE dirty/access flag support
+ * @tbre_align		- Actual TRBE alignment required for TRBPTR_EL1.
+ * @cpu			- CPU this TRBE belongs to.
+ * @mode		- Mode of current operation. (perf/disabled)
+ * @drvdata		- TRBE specific drvdata
+ * @errata		- Bit map for the errata on this TRBE.
+ */
 struct trbe_cpudata {
 	bool trbe_flag;
 	u64 trbe_align;
@@ -72,6 +103,7 @@ struct trbe_cpudata {
 	enum cs_mode mode;
 	struct trbe_buf *buf;
 	struct trbe_drvdata *drvdata;
+	DECLARE_BITMAP(errata, TRBE_ERRATA_MAX);
 };
 
 struct trbe_drvdata {
@@ -84,6 +116,21 @@ struct trbe_drvdata {
 	struct platform_device *pdev;
 };
 
+static void trbe_check_errata(struct trbe_cpudata *cpudata)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(trbe_errata_cpucaps); i++) {
+		if (this_cpu_has_cap(trbe_errata_cpucaps[i]))
+			set_bit(i, cpudata->errata);
+	}
+}
+
+static inline bool trbe_has_erratum(struct trbe_cpudata *cpudata, int i)
+{
+	return (i < TRBE_ERRATA_MAX) && test_bit(i, cpudata->errata);
+}
+
 static int trbe_alloc_node(struct perf_event *event)
 {
 	if (event->cpu == -1)
@@ -926,6 +973,8 @@ static void arm_trbe_probe_cpu(void *info)
 		pr_err("Unsupported alignment on cpu %d\n", cpu);
 		goto cpu_clear;
 	}
+
+	trbe_check_errata(cpudata);
 	cpudata->trbe_flag = get_trbe_flag_update(trbidr);
 	cpudata->cpu = cpu;
 	cpudata->drvdata = drvdata;
-- 
2.24.1