Coresight includes debug module and usually the module connects with CPU
debug logic. ARMv8 architecture reference manual (ARM DDI 0487A.k) has
description for related info in "Part H: External Debug".

Chapter H7 "The Sample-based Profiling Extension" introduces several
sampling registers, e.g. we can check program counter value with
combined CPU exception level, secure state, etc. So this is helpful for
analysis CPU lockup scenarios, e.g. if one CPU has run into infinite
loop with IRQ disabled. In this case the CPU cannot switch context and
handle any interrupt (including IPIs), as the result it cannot handle
SMP call for stack dump.

This patch is to enable coresight debug module, so firstly this driver
is to bind apb clock for debug module and this is to ensure the debug
module can be accessed from program or external debugger. And the driver
uses sample-based registers for debug purpose, e.g. when system triggers
panic, the driver will dump program counter and combined context
registers (EDCIDSR, EDVIDSR); by parsing context registers so can
quickly get to know CPU secure state, exception level, etc.

Some of the debug module registers are located in CPU power domain, so
this requires the CPU power domain stays on when access related debug
registers, but the power management for CPU power domain is quite
dependent on SoC integration for power management. For the platforms
which with sane power controller implementations, this driver follows
the method to set EDPRCR to try to pull the CPU out of low power state
and then set 'no power down request' bit so the CPU has no chance to
lose power.

If the SoC has not followed up this design well for power management
controller, the driver introduces module parameter "idle_constraint".
Setting this parameter for latency requirement in microseconds, finally
we can constrain all or partial idle states to ensure the CPU power
domain is enabled, this is a backup method to access coresight CPU
debug component safely.

Signed-off-by: Leo Yan <redacted>
---
 drivers/hwtracing/coresight/Kconfig               |  11 +
 drivers/hwtracing/coresight/Makefile              |   1 +
 drivers/hwtracing/coresight/coresight-cpu-debug.c | 704 ++++++++++++++++++++++
 3 files changed, 716 insertions(+)
 create mode 100644 drivers/hwtracing/coresight/coresight-cpu-debug.c

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index 130cb21..18d7931 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig

@@ -89,4 +89,15 @@ config CORESIGHT_STM
 	  logging useful software events or data coming from various entities
 	  in the system, possibly running different OSs
 
+config CORESIGHT_CPU_DEBUG
+	tristate "CoreSight CPU Debug driver"
+	depends on ARM || ARM64
+	depends on DEBUG_FS
+	help
+	  This driver provides support for coresight debugging module. This
+	  is primarily used to dump sample-based profiling registers when
+	  system triggers panic, the driver will parse context registers so
+	  can quickly get to know program counter (PC), secure state,
+	  exception level, etc.
+
 endif

diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
index af480d9..433d590 100644
--- a/drivers/hwtracing/coresight/Makefile
+++ b/drivers/hwtracing/coresight/Makefile

@@ -16,3 +16,4 @@ obj-$(CONFIG_CORESIGHT_SOURCE_ETM4X) += coresight-etm4x.o \
 					coresight-etm4x-sysfs.o
 obj-$(CONFIG_CORESIGHT_QCOM_REPLICATOR) += coresight-replicator-qcom.o
 obj-$(CONFIG_CORESIGHT_STM) += coresight-stm.o
+obj-$(CONFIG_CORESIGHT_CPU_DEBUG) += coresight-cpu-debug.o

diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
new file mode 100644
index 0000000..fbec1d1
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c

@@ -0,0 +1,704 @@
+/*
+ * Copyright (c) 2017 Linaro Limited. All rights reserved.
+ *
+ * Author: Leo Yan <leo.yan@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#include <linux/amba/bus.h>
+#include <linux/coresight.h>
+#include <linux/cpu.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/pm_qos.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+
+#include "coresight-priv.h"
+
+#define EDPCSR				0x0A0
+#define EDCIDSR				0x0A4
+#define EDVIDSR				0x0A8
+#define EDPCSR_HI			0x0AC
+#define EDOSLAR				0x300
+#define EDPRCR				0x310
+#define EDPRSR				0x314
+#define EDDEVID1			0xFC4
+#define EDDEVID				0xFC8
+
+#define EDPCSR_PROHIBITED		0xFFFFFFFF
+
+/* bits definition for EDPCSR */
+#ifndef CONFIG_64BIT
+#define EDPCSR_THUMB			BIT(0)
+#define EDPCSR_ARM_INST_MASK		GENMASK(31, 2)
+#define EDPCSR_THUMB_INST_MASK		GENMASK(31, 1)
+#endif
+
+/* bits definition for EDPRCR */
+#define EDPRCR_COREPURQ			BIT(3)
+#define EDPRCR_CORENPDRQ		BIT(0)
+
+/* bits definition for EDPRSR */
+#define EDPRSR_DLK			BIT(6)
+#define EDPRSR_PU			BIT(0)
+
+/* bits definition for EDVIDSR */
+#define EDVIDSR_NS			BIT(31)
+#define EDVIDSR_E2			BIT(30)
+#define EDVIDSR_E3			BIT(29)
+#define EDVIDSR_HV			BIT(28)
+#define EDVIDSR_VMID			GENMASK(7, 0)
+
+/*
+ * bits definition for EDDEVID1:PSCROffset
+ *
+ * NOTE: armv8 and armv7 have different definition for the register,
+ * so consolidate the bits definition as below:
+ *
+ * 0b0000 - Sample offset applies based on the instruction state, we
+ *          rely on EDDEVID to check if EDPCSR is implemented or not
+ * 0b0001 - No offset applies.
+ * 0b0010 - No offset applies, but do not use in AArch32 mode
+ *
+ */
+#define EDDEVID1_PCSR_OFFSET_MASK	GENMASK(3, 0)
+#define EDDEVID1_PCSR_OFFSET_INS_SET	(0x0)
+#define EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32	(0x2)
+
+/* bits definition for EDDEVID */
+#define EDDEVID_PCSAMPLE_MODE		GENMASK(3, 0)
+#define EDDEVID_IMPL_NONE		(0x0)
+#define EDDEVID_IMPL_EDPCSR		(0x1)
+#define EDDEVID_IMPL_EDPCSR_EDCIDSR	(0x2)
+#define EDDEVID_IMPL_FULL		(0x3)
+
+#define DEBUG_WAIT_TIMEOUT		32
+
+struct debug_drvdata {
+	void __iomem	*base;
+	struct device	*dev;
+	int		cpu;
+
+	bool		edpcsr_present;
+	bool		edcidsr_present;
+	bool		edvidsr_present;
+	bool		pc_has_offset;
+
+	u32		eddevid;
+	u32		eddevid1;
+
+	u32		edpcsr;
+	u32		edpcsr_hi;
+	u32		edprcr;
+	u32		edprsr;
+	u32		edvidsr;
+	u32		edcidsr;
+};
+
+static DEFINE_MUTEX(debug_lock);
+static DEFINE_PER_CPU(struct debug_drvdata *, debug_drvdata);
+static int debug_count;
+static struct dentry *debug_debugfs_dir;
+
+static struct pm_qos_request debug_qos_req;
+static int idle_constraint = PM_QOS_DEFAULT_VALUE;
+module_param(idle_constraint, int, 0600);
+MODULE_PARM_DESC(idle_constraint, "Latency requirement in microseconds for CPU "
+		 "idle states (default is -1, which means have no limiation "
+		 "to CPU idle states; 0 means disabling all idle states; user "
+		 "can choose other platform dependent values so can disable "
+		 "specific idle states for the platform)");
+