| Message ID | 1489762943-25849-5-git-send-email-leo.yan@linaro.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On 17/03/17 15:02, 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 detects > the CPU lockup and trigger panic, the driver will dump program counter Do we dump it when the CPU lockup is detected with this change ? If not, we shouldn't claim that here. > 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 > in the driver it has checked the power state for CPU before accessing > registers within CPU power domain. For most safe way to use this driver, > it's suggested to disable CPU low power states, this can simply set > "nohlt" in kernel command line. > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > drivers/hwtracing/coresight/Kconfig | 10 + > drivers/hwtracing/coresight/Makefile | 1 + > drivers/hwtracing/coresight/coresight-cpu-debug.c | 407 ++++++++++++++++++++++ > 3 files changed, 418 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..daf80bc 100644 > --- a/drivers/hwtracing/coresight/Kconfig > +++ b/drivers/hwtracing/coresight/Kconfig > @@ -89,4 +89,14 @@ config CORESIGHT_STM > logging useful software events or data coming from various entities > in the system, possibly running different OSs > > +config CORESIGHT_CPU_DEBUG > + bool "CoreSight CPU Debug driver" > + depends on ARM || ARM64 > + help > + This driver provides support for coresight debugging module. This > + is primarily used to dump sample-based profiling registers for > + panic. To avoid lockups when accessing debug module registers, > + it is safer to disable CPU low power states (like "nohlt" on the > + kernel command line) when using this feature. > + > 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 > +/* > + * bits definition for EDDEVID1 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 > + * > + */ Thanks for adding the comment here. > +#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) Do we support an implementation where only EDPCSR is implemented (0x1) ? That should be quite straight forward by adding edcidsr_present. > +#define EDDEVID_IMPL_EDPCSR_EDCIDSR (0x2) > +#define EDDEVID_IMPL_FULL (0x3) > + > +struct debug_drvdata { > + void __iomem *base; > + struct device *dev; > + int cpu; > + > + bool edpcsr_present; > + bool edvidsr_present; > + bool pc_has_offset; Unused member ? It would be good to populate these (and any other information) rather than, caching devid/devid1 (below). > + > + u32 eddevid; > + u32 eddevid1; > + > + u32 edpcsr; > + u32 edpcsr_hi; > + u32 edprsr; > + u32 edvidsr; > + u32 edcidsr; > +}; > + /* > + * 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. > + */ > + drvdata->edcidsr = readl_relaxed(drvdata->base + EDCIDSR); > +#ifdef CONFIG_64BIT > + drvdata->edpcsr_hi = readl_relaxed(drvdata->base + EDPCSR_HI); > +#endif We could use IS_ENABLED() here. > +#ifdef CONFIG_64BIT > + pc = (unsigned long)drvdata->edpcsr_hi << 32 | > + (unsigned long)drvdata->edpcsr; > +#else > + pc = debug_adjust_pc(drvdata, (unsigned long)drvdata->edpcsr); > +#endif > + > + pr_emerg("\tEDPCSR: [<%p>] %pS\n", (void *)pc, (void *)pc); Are we safe calling %pS on the PC, when the PC offset in implementation defined ? > + pr_emerg("\tEDCIDSR: %08x\n", drvdata->edcidsr); > + > + if (!drvdata->edvidsr_present) > + return; > + > + pr_emerg("\tEDVIDSR: %08x (State:%s Mode:%s Width:%s 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 ? "64bits" : "32bits", ultra minor nit: this could be also done as : "Width:%dbits" and drvdata->edvidsr & EDVISR_HW ? 64 : 32. Avoids string literal. > + drvdata->edvidsr & (u32)EDVIDSR_VMID); > +} > + > +/* > + * Dump out information on panic. > + */ > +static int debug_notifier_call(struct notifier_block *self, > + unsigned long v, void *p) > +{ > + int cpu; > + > + pr_emerg("ARM external debug module:\n"); > + > + for_each_possible_cpu(cpu) { > + if (!per_cpu(debug_drvdata, cpu)) > + continue; > + > + pr_emerg("CPU[%d]:\n", per_cpu(debug_drvdata, cpu)->cpu); > + > + debug_read_regs(per_cpu(debug_drvdata, cpu)); > + debug_dump_regs(per_cpu(debug_drvdata, cpu)); nit: It would look nicer if you could use a variable for the per_cpu(debug_drvdata, cpu), rather than repeating it every single line. > + } > + > + return 0; > +} > + > +static struct notifier_block debug_notifier = { > + .notifier_call = debug_notifier_call, > +}; > + > +static void debug_init_arch_data(void *info) > +{ > + struct debug_drvdata *drvdata = info; > + u32 mode, pcsr_offset; > + > + CS_UNLOCK(drvdata->base); > + > + debug_os_unlock(drvdata); > + > + /* Read device info */ > + drvdata->eddevid = readl_relaxed(drvdata->base + EDDEVID); > + drvdata->eddevid1 = readl_relaxed(drvdata->base + EDDEVID1); > + > + /* Parse implementation feature */ > + mode = drvdata->eddevid & EDDEVID_PCSAMPLE_MODE; > + if (mode == EDDEVID_IMPL_FULL) { > + drvdata->edpcsr_present = true; > + drvdata->edvidsr_present = true; > + } else if (mode == EDDEVID_IMPL_EDPCSR_EDCIDSR) { > + > + pcsr_offset = drvdata->eddevid1 & EDDEVID1_PCSR_OFFSET_MASK; > + > + /* > + * 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. > + */ > + if (!IS_ENABLED(CONFIG_64BIT) && > + (pcsr_offset == EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32)) > + drvdata->edpcsr_present = false; > + else > + drvdata->edpcsr_present = true; > + > + drvdata->edvidsr_present = false; > + } else { Actually, if mode == 0x01, pcsr is present, which we don't handle here. > + drvdata->edpcsr_present = false; > + drvdata->edvidsr_present = false; > + } > + > + CS_LOCK(drvdata->base); > +} > + > +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; > + static int debug_count; > + int ret; > + > + drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL); > + if (!drvdata) > + return -ENOMEM; > + > + drvdata->cpu = np ? of_coresight_get_cpu(np) : 0; > + drvdata->dev = &adev->dev; > + > + dev_set_drvdata(dev, 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; We should make sure that there is no debug_drvdata already set for the CPU. (e.g, if the cpu node is missing for two CPUs, we could end up in two drvdata for CPU0 and thus leaking the memory allocated for the first one). Suzuki -- To unsubscribe from this list: send the line "unsubscribe linux-clk" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Mar 17, 2017 at 06:44:03PM +0000, Suzuki K Poulose wrote: > On 17/03/17 15:02, 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 detects > >the CPU lockup and trigger panic, the driver will dump program counter > > Do we dump it when the CPU lockup is detected with this change ? If not, > we shouldn't claim that here. Right, the mainline kernel missed Colin Cross's patch to trigger panic when detect CPU lockup which used by Android common kernel: http://people.linaro.org/~leo.yan/0001-hardlockup-detect-hard-lockups-without-NMIs-using-se.patch Will fix it. [...] > >+ pr_emerg("\tEDPCSR: [<%p>] %pS\n", (void *)pc, (void *)pc); > > Are we safe calling %pS on the PC, when the PC offset in implementation defined ? I did some quick testing, if cannot find proper kernel symbol for PC value, then %pS will directly output pc value rather than symbol value. Other suggestions are good for me; I will fix for all for them. [...] Thanks, Leo Yan -- To unsubscribe from this list: send the line "unsubscribe linux-clk" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig index 130cb21..daf80bc 100644 --- a/drivers/hwtracing/coresight/Kconfig +++ b/drivers/hwtracing/coresight/Kconfig @@ -89,4 +89,14 @@ config CORESIGHT_STM logging useful software events or data coming from various entities in the system, possibly running different OSs +config CORESIGHT_CPU_DEBUG + bool "CoreSight CPU Debug driver" + depends on ARM || ARM64 + help + This driver provides support for coresight debugging module. This + is primarily used to dump sample-based profiling registers for + panic. To avoid lockups when accessing debug module registers, + it is safer to disable CPU low power states (like "nohlt" on the + kernel command line) when using this feature. + 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..bb1c5b6 --- /dev/null +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c @@ -0,0 +1,407 @@ +/* + * 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/device.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/moduleparam.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 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 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 + * + * 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_EDCIDSR (0x2) +#define EDDEVID_IMPL_FULL (0x3) + +struct debug_drvdata { + void __iomem *base; + struct device *dev; + int cpu; + + bool edpcsr_present; + bool edvidsr_present; + bool pc_has_offset; + + u32 eddevid; + u32 eddevid1; + + u32 edpcsr; + u32 edpcsr_hi; + u32 edprsr; + u32 edvidsr; + u32 edcidsr; +}; + +static DEFINE_PER_CPU(struct debug_drvdata *, debug_drvdata); + +static void debug_os_unlock(struct debug_drvdata *drvdata) +{ + /* Unlocks the debug registers */ + writel_relaxed(0x0, drvdata->base + EDOSLAR); + 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_read_regs(struct debug_drvdata *drvdata) +{ + drvdata->edprsr = readl_relaxed(drvdata->base + EDPRSR); + + if (!debug_access_permitted(drvdata)) + return; + + if (!drvdata->edpcsr_present) + return; + + CS_UNLOCK(drvdata->base); + + debug_os_unlock(drvdata); + + 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) { + CS_LOCK(drvdata->base); + return; + } + + /* + * 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. + */ + drvdata->edcidsr = readl_relaxed(drvdata->base + EDCIDSR); +#ifdef CONFIG_64BIT + drvdata->edpcsr_hi = readl_relaxed(drvdata->base + EDPCSR_HI); +#endif + + if (drvdata->edvidsr_present) + drvdata->edvidsr = readl_relaxed(drvdata->base + EDVIDSR); + + CS_LOCK(drvdata->base); +} + +#ifndef CONFIG_64BIT +static bool debug_pc_has_offset(struct debug_drvdata *drvdata) +{ + u32 pcsr_offset; + + pcsr_offset = drvdata->eddevid1 & EDDEVID1_PCSR_OFFSET_MASK; + + return (pcsr_offset == EDDEVID1_PCSR_OFFSET_INS_SET); +} + +static unsigned long debug_adjust_pc(struct debug_drvdata *drvdata, + unsigned long pc) +{ + unsigned long arm_inst_offset = 0, thumb_inst_offset = 0; + + if (debug_pc_has_offset(drvdata)) { + 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; +} +#endif + +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) || !drvdata->edpcsr_present) { + 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; + } + +#ifdef CONFIG_64BIT + pc = (unsigned long)drvdata->edpcsr_hi << 32 | + (unsigned long)drvdata->edpcsr; +#else + pc = debug_adjust_pc(drvdata, (unsigned long)drvdata->edpcsr); +#endif + + pr_emerg("\tEDPCSR: [<%p>] %pS\n", (void *)pc, (void *)pc); + pr_emerg("\tEDCIDSR: %08x\n", drvdata->edcidsr); + + if (!drvdata->edvidsr_present) + return; + + pr_emerg("\tEDVIDSR: %08x (State:%s Mode:%s Width:%s 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 ? "64bits" : "32bits", + drvdata->edvidsr & (u32)EDVIDSR_VMID); +} + +/* + * Dump out information on panic. + */ +static int debug_notifier_call(struct notifier_block *self, + unsigned long v, void *p) +{ + int cpu; + + pr_emerg("ARM external debug module:\n"); + + for_each_possible_cpu(cpu) { + if (!per_cpu(debug_drvdata, cpu)) + continue; + + pr_emerg("CPU[%d]:\n", per_cpu(debug_drvdata, cpu)->cpu); + + debug_read_regs(per_cpu(debug_drvdata, cpu)); + debug_dump_regs(per_cpu(debug_drvdata, cpu)); + } + + return 0; +} + +static struct notifier_block debug_notifier = { + .notifier_call = debug_notifier_call, +}; + +static void debug_init_arch_data(void *info) +{ + struct debug_drvdata *drvdata = info; + u32 mode, pcsr_offset; + + CS_UNLOCK(drvdata->base); + + debug_os_unlock(drvdata); + + /* Read device info */ + drvdata->eddevid = readl_relaxed(drvdata->base + EDDEVID); + drvdata->eddevid1 = readl_relaxed(drvdata->base + EDDEVID1); + + /* Parse implementation feature */ + mode = drvdata->eddevid & EDDEVID_PCSAMPLE_MODE; + if (mode == EDDEVID_IMPL_FULL) { + drvdata->edpcsr_present = true; + drvdata->edvidsr_present = true; + } else if (mode == EDDEVID_IMPL_EDPCSR_EDCIDSR) { + + pcsr_offset = drvdata->eddevid1 & EDDEVID1_PCSR_OFFSET_MASK; + + /* + * 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. + */ + if (!IS_ENABLED(CONFIG_64BIT) && + (pcsr_offset == EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32)) + drvdata->edpcsr_present = false; + else + drvdata->edpcsr_present = true; + + drvdata->edvidsr_present = false; + } else { + drvdata->edpcsr_present = false; + drvdata->edvidsr_present = false; + } + + CS_LOCK(drvdata->base); +} + +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; + static int debug_count; + int ret; + + drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL); + if (!drvdata) + return -ENOMEM; + + drvdata->cpu = np ? of_coresight_get_cpu(np) : 0; + drvdata->dev = &adev->dev; + + dev_set_drvdata(dev, 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, "Debug arch init failed\n"); + return ret; + } + + if (!drvdata->edpcsr_present) { + dev_err(dev, "Sample-based profiling is not implemented\n"); + return -ENXIO; + } + + if (!debug_count++) + atomic_notifier_chain_register(&panic_notifier_list, + &debug_notifier); + + dev_info(dev, "Coresight debug-CPU%d initialized\n", drvdata->cpu); + 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, + .id_table = debug_ids, +}; +builtin_amba_driver(debug_driver);
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 detects the CPU lockup and trigger 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 in the driver it has checked the power state for CPU before accessing registers within CPU power domain. For most safe way to use this driver, it's suggested to disable CPU low power states, this can simply set "nohlt" in kernel command line. Signed-off-by: Leo Yan <leo.yan@linaro.org> --- drivers/hwtracing/coresight/Kconfig | 10 + drivers/hwtracing/coresight/Makefile | 1 + drivers/hwtracing/coresight/coresight-cpu-debug.c | 407 ++++++++++++++++++++++ 3 files changed, 418 insertions(+) create mode 100644 drivers/hwtracing/coresight/coresight-cpu-debug.c