Re: [PATCH v9 7/9] coresight: add support for CPU debug module

[Mathieu Poirier]

On Tue, May 09, 2017 at 10:50:00AM +0800, Leo Yan wrote:
> 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 user should use the command line parameter or sysfs
> to constrain all or partial idle states to ensure the CPU power
> domain is enabled and access coresight CPU debug component safely.
> 
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
>  drivers/hwtracing/coresight/Kconfig               |  14 +
>  drivers/hwtracing/coresight/Makefile              |   1 +
>  drivers/hwtracing/coresight/coresight-cpu-debug.c | 693 ++++++++++++++++++++++
>  3 files changed, 708 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..8d55d6d 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -89,4 +89,18 @@ 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. Before use debugging functionality, platform
> +	  needs to ensure the clock domain and power domain are enabled
> +	  properly, please refer Documentation/trace/coresight-cpu-debug.txt
> +	  for detailed description and the example for usage.
> +
>  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..ab12ec1
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> @@ -0,0 +1,693 @@
> +/*
> + * Copyright (c) 2017 Linaro Limited. All rights reserved.
> + *
> + * Author: Leo Yan <leo.yan@xxxxxxxxxx>
> + *
> + * 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/iopoll.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 */
> +#define EDPCSR_THUMB			BIT(0)
> +#define EDPCSR_ARM_INST_MASK		GENMASK(31, 2)
> +#define EDPCSR_THUMB_INST_MASK		GENMASK(31, 1)
> +
> +/* 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_EDPCSR		(0x1)
> +#define EDDEVID_IMPL_EDPCSR_EDCIDSR	(0x2)
> +#define EDDEVID_IMPL_FULL		(0x3)
> +
> +#define DEBUG_WAIT_SLEEP		1000
> +#define DEBUG_WAIT_TIMEOUT		32000
> +
> +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		edpcsr;
> +	u32		edpcsr_hi;
> +	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 bool debug_enable;
> +module_param_named(enable, debug_enable, bool, 0600);
> +MODULE_PARM_DESC(enable, "Knob to enable debug functionality "
> +		 "(default is 0, which means is disabled by default)");
> +
> +static void debug_os_unlock(struct debug_drvdata *drvdata)
> +{
> +	/* Unlocks the debug registers */
> +	writel_relaxed(0x0, drvdata->base + EDOSLAR);
> +
> +	/* Make sure the registers are unlocked before accessing */
> +	wmb();
> +}
> +
> +/*
> + * According to ARM DDI 0487A.k, before access external debug
> + * registers should firstly check the access permission; if any
> + * below condition has been met then cannot access debug
> + * registers to avoid lockup issue:
> + *
> + * - CPU power domain is powered off;
> + * - The OS Double Lock is locked;
> + *
> + * By checking EDPRSR can get to know if meet these conditions.
> + */
> +static bool debug_access_permitted(struct debug_drvdata *drvdata)
> +{
> +	/* CPU is powered off */
> +	if (!(drvdata->edprsr & EDPRSR_PU))
> +		return false;
> +
> +	/* The OS Double Lock is locked */
> +	if (drvdata->edprsr & EDPRSR_DLK)
> +		return false;
> +
> +	return true;
> +}
> +
> +static void debug_force_cpu_powered_up(struct debug_drvdata *drvdata)
> +{
> +	u32 edprcr;
> +
> +try_again:
> +
> +	/*
> +	 * Send request to power management controller and assert
> +	 * DBGPWRUPREQ signal; if power management controller has
> +	 * sane implementation, it should enable CPU power domain
> +	 * in case CPU is in low power state.
> +	 */
> +	edprcr = readl_relaxed(drvdata->base + EDPRCR);
> +	edprcr |= EDPRCR_COREPURQ;
> +	writel_relaxed(edprcr, drvdata->base + EDPRCR);
> +
> +	/* Wait for CPU to be powered up (timeout~=32ms) */
> +	if (readx_poll_timeout_atomic(readl_relaxed, drvdata->base + EDPRSR,
> +			drvdata->edprsr, (drvdata->edprsr & EDPRSR_PU),
> +			DEBUG_WAIT_SLEEP, DEBUG_WAIT_TIMEOUT)) {
> +		/*
> +		 * Unfortunately the CPU cannot be powered up, so return
> +		 * back and later has no permission to access other
> +		 * registers. For this case, should disable CPU low power
> +		 * states to ensure CPU power domain is enabled!
> +		 */
> +		pr_err("%s: power up request for CPU%d failed\n",
> +			__func__, drvdata->cpu);
> +		return;
> +	}
> +
> +	/*
> +	 * At this point the CPU is powered up, so set the no powerdown
> +	 * request bit so we don't lose power and emulate power down.
> +	 */
> +	edprcr = readl_relaxed(drvdata->base + EDPRCR);
> +	edprcr |= EDPRCR_COREPURQ | EDPRCR_CORENPDRQ;
> +	writel_relaxed(edprcr, drvdata->base + EDPRCR);
> +
> +	drvdata->edprsr = readl_relaxed(drvdata->base + EDPRSR);
> +
> +	/* The core power domain got switched off on use, try again */
> +	if (unlikely(!(drvdata->edprsr & EDPRSR_PU)))
> +		goto try_again;
> +}
> +
> +static void debug_read_regs(struct debug_drvdata *drvdata)
> +{
> +	u32 save_edprcr;
> +
> +	CS_UNLOCK(drvdata->base);
> +
> +	/* Unlock os lock */
> +	debug_os_unlock(drvdata);
> +
> +	/* Save EDPRCR register */
> +	save_edprcr = readl_relaxed(drvdata->base + EDPRCR);
> +
> +	/*
> +	 * Ensure CPU power domain is enabled to let registers
> +	 * are accessiable.
> +	 */
> +	debug_force_cpu_powered_up(drvdata);
> +
> +	if (!debug_access_permitted(drvdata))
> +		goto out;
> +
> +	drvdata->edpcsr = readl_relaxed(drvdata->base + EDPCSR);
> +
> +	/*
> +	 * As described in ARM DDI 0487A.k, if the processing
> +	 * element (PE) is in debug state, or sample-based
> +	 * profiling is prohibited, EDPCSR reads as 0xFFFFFFFF;
> +	 * EDCIDSR, EDVIDSR and EDPCSR_HI registers also become
> +	 * UNKNOWN state. So directly bail out for this case.
> +	 */
> +	if (drvdata->edpcsr == EDPCSR_PROHIBITED)
> +		goto out;
> +
> +	/*
> +	 * A read of the EDPCSR normally has the side-effect of
> +	 * indirectly writing to EDCIDSR, EDVIDSR and EDPCSR_HI;
> +	 * at this point it's safe to read value from them.
> +	 */
> +	if (IS_ENABLED(CONFIG_64BIT))
> +		drvdata->edpcsr_hi = readl_relaxed(drvdata->base + EDPCSR_HI);
> +
> +	if (drvdata->edcidsr_present)
> +		drvdata->edcidsr = readl_relaxed(drvdata->base + EDCIDSR);
> +
> +	if (drvdata->edvidsr_present)
> +		drvdata->edvidsr = readl_relaxed(drvdata->base + EDVIDSR);
> +
> +out:
> +	/* Restore EDPRCR register */
> +	writel_relaxed(save_edprcr, drvdata->base + EDPRCR);
> +
> +	CS_LOCK(drvdata->base);
> +}
> +
> +static unsigned long debug_adjust_pc(struct debug_drvdata *drvdata)
> +{
> +	unsigned long arm_inst_offset = 0, thumb_inst_offset = 0;
> +	unsigned long pc;
> +
> +	if (IS_ENABLED(CONFIG_64BIT))
> +		return (unsigned long)drvdata->edpcsr_hi << 32 |
> +		       (unsigned long)drvdata->edpcsr;
> +
> +	pc = (unsigned long)drvdata->edpcsr;
> +
> +	if (drvdata->pc_has_offset) {
> +		arm_inst_offset = 8;
> +		thumb_inst_offset = 4;
> +	}
> +
> +	/* Handle thumb instruction */
> +	if (pc & EDPCSR_THUMB) {
> +		pc = (pc & EDPCSR_THUMB_INST_MASK) - thumb_inst_offset;
> +		return pc;
> +	}
> +
> +	/*
> +	 * Handle arm instruction offset, if the arm instruction
> +	 * is not 4 byte alignment then it's possible the case
> +	 * for implementation defined; keep original value for this
> +	 * case and print info for notice.
> +	 */
> +	if (pc & BIT(1))
> +		pr_emerg("Instruction offset is implementation defined\n");
> +	else
> +		pc = (pc & EDPCSR_ARM_INST_MASK) - arm_inst_offset;
> +
> +	return pc;
> +}
> +
> +static void debug_dump_regs(struct debug_drvdata *drvdata)
> +{
> +	unsigned long pc;
> +
> +	pr_emerg("\tEDPRSR:  %08x (Power:%s DLK:%s)\n", drvdata->edprsr,
> +		 drvdata->edprsr & EDPRSR_PU ? "On" : "Off",
> +		 drvdata->edprsr & EDPRSR_DLK ? "Lock" : "Unlock");
> +
> +	if (!debug_access_permitted(drvdata)) {
> +		pr_emerg("No permission to access debug registers!\n");
> +		return;
> +	}
> +
> +	if (drvdata->edpcsr == EDPCSR_PROHIBITED) {
> +		pr_emerg("CPU is in Debug state or profiling is prohibited!\n");
> +		return;
> +	}
> +
> +	pc = debug_adjust_pc(drvdata);
> +	pr_emerg("\tEDPCSR:  [<%p>] %pS\n", (void *)pc, (void *)pc);
> +
> +	if (drvdata->edcidsr_present)
> +		pr_emerg("\tEDCIDSR: %08x\n", drvdata->edcidsr);
> +
> +	if (drvdata->edvidsr_present)
> +		pr_emerg("\tEDVIDSR: %08x (State:%s Mode:%s Width:%dbits VMID:%x)\n",
> +			 drvdata->edvidsr,
> +			 drvdata->edvidsr & EDVIDSR_NS ? "Non-secure" : "Secure",
> +			 drvdata->edvidsr & EDVIDSR_E3 ? "EL3" :
> +				(drvdata->edvidsr & EDVIDSR_E2 ? "EL2" : "EL1/0"),
> +			 drvdata->edvidsr & EDVIDSR_HV ? 64 : 32,
> +			 drvdata->edvidsr & (u32)EDVIDSR_VMID);
> +}
> +
> +static void debug_init_arch_data(void *info)
> +{
> +	struct debug_drvdata *drvdata = info;
> +	u32 mode, pcsr_offset;
> +	u32 eddevid, eddevid1;
> +
> +	CS_UNLOCK(drvdata->base);
> +
> +	/* Read device info */
> +	eddevid  = readl_relaxed(drvdata->base + EDDEVID);
> +	eddevid1 = readl_relaxed(drvdata->base + EDDEVID1);
> +
> +	CS_LOCK(drvdata->base);
> +
> +	/* Parse implementation feature */
> +	mode = eddevid & EDDEVID_PCSAMPLE_MODE;
> +	pcsr_offset = eddevid1 & EDDEVID1_PCSR_OFFSET_MASK;
> +
> +	drvdata->edpcsr_present  = false;
> +	drvdata->edcidsr_present = false;
> +	drvdata->edvidsr_present = false;
> +	drvdata->pc_has_offset   = false;
> +
> +	switch (mode) {
> +	case EDDEVID_IMPL_FULL:
> +		drvdata->edvidsr_present = true;
> +		/* Fall through */
> +	case EDDEVID_IMPL_EDPCSR_EDCIDSR:
> +		drvdata->edcidsr_present = true;
> +		/* Fall through */
> +	case EDDEVID_IMPL_EDPCSR:
> +		/*
> +		 * In ARM DDI 0487A.k, the EDDEVID1.PCSROffset is used to
> +		 * define if has the offset for PC sampling value; if read
> +		 * back EDDEVID1.PCSROffset == 0x2, then this means the debug
> +		 * module does not sample the instruction set state when
> +		 * armv8 CPU in AArch32 state.
> +		 */
> +		drvdata->edpcsr_present =
> +			((IS_ENABLED(CONFIG_64BIT) && pcsr_offset != 0) ||
> +			 (pcsr_offset != EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32));
> +
> +		drvdata->pc_has_offset =
> +			(pcsr_offset == EDDEVID1_PCSR_OFFSET_INS_SET);
> +		break;
> +	default:
> +		break;
> +	}
> +}
> +
> +/*
> + * Dump out information on panic.
> + */
> +static int debug_notifier_call(struct notifier_block *self,
> +			       unsigned long v, void *p)
> +{
> +	int cpu;
> +	struct debug_drvdata *drvdata;
> +
> +	mutex_lock(&debug_lock);
> +
> +	/* Bail out if the functionality is disabled */
> +	if (!debug_enable)
> +		goto skip_dump;
> +
> +	pr_emerg("ARM external debug module:\n");
> +
> +	for_each_possible_cpu(cpu) {
> +		drvdata = per_cpu(debug_drvdata, cpu);
> +		if (!drvdata)
> +			continue;
> +
> +		pr_emerg("CPU[%d]:\n", drvdata->cpu);
> +
> +		debug_read_regs(drvdata);
> +		debug_dump_regs(drvdata);
> +	}
> +
> +skip_dump:
> +	mutex_unlock(&debug_lock);
> +	return 0;
> +}
> +
> +static struct notifier_block debug_notifier = {
> +	.notifier_call = debug_notifier_call,
> +};
> +
> +static int debug_enable_func(void)
> +{
> +	struct debug_drvdata *drvdata;
> +	int cpu, ret = 0;
> +	cpumask_t mask;
> +
> +	/*
> +	 * Use cpumask to track which debug power domains have
> +	 * been powered on and use it to handle failure case.
> +	 */
> +	cpumask_clear(&mask);
> +
> +	for_each_possible_cpu(cpu) {
> +		drvdata = per_cpu(debug_drvdata, cpu);
> +		if (!drvdata)
> +			continue;
> +
> +		ret = pm_runtime_get_sync(drvdata->dev);
> +		if (ret < 0)
> +			goto err;
> +		else
> +			cpumask_set_cpu(cpu, &mask);
> +	}
> +
> +	return 0;
> +
> +err:
> +	/*
> +	 * If pm_runtime_get_sync() has failed, need rollback on
> +	 * all the other CPUs that have been enabled before that.
> +	 */
> +	for_each_cpu(cpu, &mask) {
> +		drvdata = per_cpu(debug_drvdata, cpu);
> +		pm_runtime_put_noidle(drvdata->dev);
> +	}
> +
> +	return ret;
> +}
> +
> +static int debug_disable_func(void)
> +{
> +	struct debug_drvdata *drvdata;
> +	int cpu, ret, err = 0;
> +
> +	/*
> +	 * Disable debug power domains, records the error and keep
> +	 * circling through all other CPUs when an error has been
> +	 * encountered.
> +	 */
> +	for_each_possible_cpu(cpu) {
> +		drvdata = per_cpu(debug_drvdata, cpu);
> +		if (!drvdata)
> +			continue;
> +
> +		ret = pm_runtime_put(drvdata->dev);
> +		if (ret < 0)
> +			err = ret;
> +	}
> +
> +	return err;
> +}
> +
> +static ssize_t debug_func_knob_write(struct file *f,
> +		const char __user *buf, size_t count, loff_t *ppos)
> +{
> +	u8 val;
> +	int ret;
> +
> +	ret = kstrtou8_from_user(buf, count, 2, &val);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&debug_lock);
> +
> +	if (val == debug_enable)
> +		goto out;
> +
> +	if (val)
> +		ret = debug_enable_func();
> +	else
> +		ret = debug_disable_func();
> +
> +	if (ret) {
> +		pr_err("%s: unable to %s debug function: %d\n",
> +		       __func__, val ? "enable" : "disable", ret);
> +		goto err;
> +	}
> +
> +	debug_enable = val;
> +out:
> +	ret = count;
> +err:
> +	mutex_unlock(&debug_lock);
> +	return ret;
> +}
> +
> +static ssize_t debug_func_knob_read(struct file *f,
> +		char __user *ubuf, size_t count, loff_t *ppos)
> +{
> +	ssize_t ret;
> +	char buf[3];
> +
> +	mutex_lock(&debug_lock);
> +	snprintf(buf, sizeof(buf), "%d\n", debug_enable);
> +	mutex_unlock(&debug_lock);
> +
> +	ret = simple_read_from_buffer(ubuf, count, ppos, buf, sizeof(buf));
> +	return ret;
> +}
> +
> +static const struct file_operations debug_func_knob_fops = {
> +	.open	= simple_open,
> +	.read	= debug_func_knob_read,
> +	.write	= debug_func_knob_write,
> +};
> +
> +static int debug_func_init(void)
> +{
> +	struct dentry *file;
> +	int ret;
> +
> +	/* Create debugfs node */
> +	debug_debugfs_dir = debugfs_create_dir("coresight_cpu_debug", NULL);
> +	if (!debug_debugfs_dir) {
> +		pr_err("%s: unable to create debugfs directory\n", __func__);
> +		return -ENOMEM;
> +	}
> +
> +	file = debugfs_create_file("enable", 0644, debug_debugfs_dir, NULL,
> +				   &debug_func_knob_fops);
> +	if (!file) {
> +		pr_err("%s: unable to create enable knob file\n", __func__);
> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	/* Register function to be called for panic */
> +	ret = atomic_notifier_chain_register(&panic_notifier_list,
> +					     &debug_notifier);
> +	if (ret) {
> +		pr_err("%s: unable to register notifier: %d\n",
> +		       __func__, ret);
> +		goto err;
> +	}
> +
> +	return 0;
> +
> +err:
> +	debugfs_remove_recursive(debug_debugfs_dir);
> +	return ret;
> +}
> +
> +static void debug_func_exit(void)
> +{
> +	atomic_notifier_chain_unregister(&panic_notifier_list,
> +					 &debug_notifier);
> +	debugfs_remove_recursive(debug_debugfs_dir);
> +}
> +
> +static int debug_probe(struct amba_device *adev, const struct amba_id *id)
> +{
> +	void __iomem *base;
> +	struct device *dev = &adev->dev;
> +	struct debug_drvdata *drvdata;
> +	struct resource *res = &adev->res;
> +	struct device_node *np = adev->dev.of_node;
> +	int ret;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->cpu = np ? of_coresight_get_cpu(np) : 0;
> +	if (per_cpu(debug_drvdata, drvdata->cpu)) {
> +		dev_err(dev, "CPU%d drvdata has been initialized, "

s/"has been"/"has already been"

That way it really look like an error message.

Also debug_probe() uses dev_xyz() but everywhere else in the driver it is
pr_xyz() - any specific reason for that?  I suggest moving to dev_xyz().

Otherwise things look good.

Thanks,
Mathieu

> +			"may be caused by binding wrong CPU node in the DT\n",
> +			drvdata->cpu);
> +		return -EBUSY;
> +	}
> +
> +	drvdata->dev = &adev->dev;
> +	amba_set_drvdata(adev, drvdata);
> +
> +	/* Validity for the resource is already checked by the AMBA core */
> +	base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	drvdata->base = base;
> +
> +	get_online_cpus();
> +	per_cpu(debug_drvdata, drvdata->cpu) = drvdata;
> +	ret = smp_call_function_single(drvdata->cpu, debug_init_arch_data,
> +				       drvdata, 1);
> +	put_online_cpus();
> +
> +	if (ret) {
> +		dev_err(dev, "CPU%d debug arch init failed\n", drvdata->cpu);
> +		goto err;
> +	}
> +
> +	if (!drvdata->edpcsr_present) {
> +		dev_err(dev, "CPU%d sample-based profiling isn't implemented\n",
> +			drvdata->cpu);
> +		ret = -ENXIO;
> +		goto err;
> +	}
> +
> +	if (!debug_count++) {
> +		ret = debug_func_init();
> +		if (ret)
> +			goto err_func_init;
> +	}
> +
> +	mutex_lock(&debug_lock);
> +	/* Turn off debug power domain if debugging is disabled */
> +	if (!debug_enable)
> +		pm_runtime_put(dev);
> +	mutex_unlock(&debug_lock);
> +
> +	dev_info(dev, "Coresight debug-CPU%d initialized\n", drvdata->cpu);
> +	return 0;
> +
> +err_func_init:
> +	debug_count--;
> +err:
> +	per_cpu(debug_drvdata, drvdata->cpu) = NULL;
> +	return ret;
> +}
> +
> +static int debug_remove(struct amba_device *adev)
> +{
> +	struct device *dev = &adev->dev;
> +	struct debug_drvdata *drvdata = amba_get_drvdata(adev);
> +
> +	per_cpu(debug_drvdata, drvdata->cpu) = NULL;
> +
> +	mutex_lock(&debug_lock);
> +	/* Turn off debug power domain before rmmod the module */
> +	if (debug_enable)
> +		pm_runtime_put(dev);
> +	mutex_unlock(&debug_lock);
> +
> +	if (!--debug_count)
> +		debug_func_exit();
> +
> +	return 0;
> +}
> +
> +static struct amba_id debug_ids[] = {
> +	{       /* Debug for Cortex-A53 */
> +		.id	= 0x000bbd03,
> +		.mask	= 0x000fffff,
> +	},
> +	{       /* Debug for Cortex-A57 */
> +		.id	= 0x000bbd07,
> +		.mask	= 0x000fffff,
> +	},
> +	{       /* Debug for Cortex-A72 */
> +		.id	= 0x000bbd08,
> +		.mask	= 0x000fffff,
> +	},
> +	{ 0, 0 },
> +};
> +
> +static struct amba_driver debug_driver = {
> +	.drv = {
> +		.name   = "coresight-cpu-debug",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe		= debug_probe,
> +	.remove		= debug_remove,
> +	.id_table	= debug_ids,
> +};
> +
> +module_amba_driver(debug_driver);
> +
> +MODULE_AUTHOR("Leo Yan <leo.yan@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("ARM Coresight CPU Debug Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.7.4
>