[v6,1/3] coresight: etm4x: save/restore state across CPU low power states
diff mbox series

Message ID 20190913115312.12943-2-andrew.murray@arm.com
State New
Headers show
Series
  • coresight: etm4x: save/restore ETMv4 context across CPU low power states
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Commit Message

Andrew Murray Sept. 13, 2019, 11:53 a.m. UTC
Some hardware will ignore bit TRCPDCR.PU which is used to signal
to hardware that power should not be removed from the trace unit.
Let's mitigate against this by conditionally saving and restoring
the trace unit state when the CPU enters low power states.

This patchset introduces a firmware property named
'arm,coresight-loses-context-with-cpu' - when this is present the
hardware state will be conditionally saved and restored.

A module parameter 'pm_save_enable' is also introduced which can
be configured to override the firmware property. This can be set
to never allow save/restore or to conditionally allow it (only for
self-hosted). The default value is determined by firmware.

We avoid saving the hardware state when self-hosted coresight isn't
in use to reduce PM latency - we can't determine this by reading the
claim tags (TRCCLAIMCLR) as these are 'trace' registers which need
power and clocking, something we can't easily provide in the PM
context. Therefore we rely on the existing drvdata->mode internal
state that is set when self-hosted coresight is used (and powered).

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 318 ++++++++++++++++++
 drivers/hwtracing/coresight/coresight-etm4x.h |  64 ++++
 drivers/hwtracing/coresight/coresight.c       |   6 +
 include/linux/coresight.h                     |   6 +
 4 files changed, 394 insertions(+)

Patch
diff mbox series

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index a128b5063f46..4cecabdd051b 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -18,6 +18,7 @@ 
 #include <linux/stat.h>
 #include <linux/clk.h>
 #include <linux/cpu.h>
+#include <linux/cpu_pm.h>
 #include <linux/coresight.h>
 #include <linux/coresight-pmu.h>
 #include <linux/pm_wakeup.h>
@@ -26,6 +27,7 @@ 
 #include <linux/uaccess.h>
 #include <linux/perf_event.h>
 #include <linux/pm_runtime.h>
+#include <linux/property.h>
 #include <asm/sections.h>
 #include <asm/local.h>
 #include <asm/virt.h>
@@ -37,6 +39,15 @@  static int boot_enable;
 module_param(boot_enable, int, 0444);
 MODULE_PARM_DESC(boot_enable, "Enable tracing on boot");
 
+#define PARAM_PM_SAVE_FIRMWARE	  0 /* save self-hosted state as per firmware */
+#define PARAM_PM_SAVE_NEVER	  1 /* never save any state */
+#define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */
+
+static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE;
+module_param(pm_save_enable, int, 0444);
+MODULE_PARM_DESC(pm_save_enable,
+	"Save/restore state on power down: 1 = never, 2 = self-hosted");
+
 /* The number of ETMv4 currently registered */
 static int etm4_count;
 static struct etmv4_drvdata *etmdrvdata[NR_CPUS];
@@ -54,6 +65,14 @@  static void etm4_os_unlock(struct etmv4_drvdata *drvdata)
 	isb();
 }
 
+static void etm4_os_lock(struct etmv4_drvdata *drvdata)
+{
+	/* Writing 0x1 to TRCOSLAR locks the trace registers */
+	writel_relaxed(0x1, drvdata->base + TRCOSLAR);
+	drvdata->os_unlock = false;
+	isb();
+}
+
 static bool etm4_arch_supported(u8 arch)
 {
 	/* Mask out the minor version number */
@@ -1085,6 +1104,288 @@  static void etm4_init_trace_id(struct etmv4_drvdata *drvdata)
 	drvdata->trcid = coresight_get_trace_id(drvdata->cpu);
 }
 
+#ifdef CONFIG_CPU_PM
+static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
+{
+	int i, ret = 0;
+	struct etmv4_save_state *state;
+	struct device *etm_dev = &drvdata->csdev->dev;
+
+	/*
+	 * As recommended by 3.4.1 ("The procedure when powering down the PE")
+	 * of ARM IHI 0064D
+	 */
+	dsb(sy);
+	isb();
+
+	CS_UNLOCK(drvdata->base);
+
+	/* Lock the OS lock to disable trace and external debugger access */
+	etm4_os_lock(drvdata);
+
+	/* wait for TRCSTATR.PMSTABLE to go up */
+	if (coresight_timeout(drvdata->base, TRCSTATR,
+			      TRCSTATR_PMSTABLE_BIT, 1)) {
+		dev_err(etm_dev,
+			"timeout while waiting for PM Stable Status\n");
+		etm4_os_unlock(drvdata);
+		ret = -EBUSY;
+		goto out;
+	}
+
+	state = drvdata->save_state;
+
+	state->trcprgctlr = readl(drvdata->base + TRCPRGCTLR);
+	state->trcprocselr = readl(drvdata->base + TRCPROCSELR);
+	state->trcconfigr = readl(drvdata->base + TRCCONFIGR);
+	state->trcauxctlr = readl(drvdata->base + TRCAUXCTLR);
+	state->trceventctl0r = readl(drvdata->base + TRCEVENTCTL0R);
+	state->trceventctl1r = readl(drvdata->base + TRCEVENTCTL1R);
+	state->trcstallctlr = readl(drvdata->base + TRCSTALLCTLR);
+	state->trctsctlr = readl(drvdata->base + TRCTSCTLR);
+	state->trcsyncpr = readl(drvdata->base + TRCSYNCPR);
+	state->trcccctlr = readl(drvdata->base + TRCCCCTLR);
+	state->trcbbctlr = readl(drvdata->base + TRCBBCTLR);
+	state->trctraceidr = readl(drvdata->base + TRCTRACEIDR);
+	state->trcqctlr = readl(drvdata->base + TRCQCTLR);
+
+	state->trcvictlr = readl(drvdata->base + TRCVICTLR);
+	state->trcviiectlr = readl(drvdata->base + TRCVIIECTLR);
+	state->trcvissctlr = readl(drvdata->base + TRCVISSCTLR);
+	state->trcvipcssctlr = readl(drvdata->base + TRCVIPCSSCTLR);
+	state->trcvdctlr = readl(drvdata->base + TRCVDCTLR);
+	state->trcvdsacctlr = readl(drvdata->base + TRCVDSACCTLR);
+	state->trcvdarcctlr = readl(drvdata->base + TRCVDARCCTLR);
+
+	for (i = 0; i < drvdata->nrseqstate; i++)
+		state->trcseqevr[i] = readl(drvdata->base + TRCSEQEVRn(i));
+
+	state->trcseqrstevr = readl(drvdata->base + TRCSEQRSTEVR);
+	state->trcseqstr = readl(drvdata->base + TRCSEQSTR);
+	state->trcextinselr = readl(drvdata->base + TRCEXTINSELR);
+
+	for (i = 0; i < drvdata->nr_cntr; i++) {
+		state->trccntrldvr[i] = readl(drvdata->base + TRCCNTRLDVRn(i));
+		state->trccntctlr[i] = readl(drvdata->base + TRCCNTCTLRn(i));
+		state->trccntvr[i] = readl(drvdata->base + TRCCNTVRn(i));
+	}
+
+	for (i = 0; i < drvdata->nr_resource * 2; i++)
+		state->trcrsctlr[i] = readl(drvdata->base + TRCRSCTLRn(i));
+
+	for (i = 0; i < drvdata->nr_ss_cmp; i++) {
+		state->trcssccr[i] = readl(drvdata->base + TRCSSCCRn(i));
+		state->trcsscsr[i] = readl(drvdata->base + TRCSSCSRn(i));
+		state->trcsspcicr[i] = readl(drvdata->base + TRCSSPCICRn(i));
+	}
+
+	for (i = 0; i < drvdata->nr_addr_cmp * 2; i++) {
+		state->trcacvr[i] = readl(drvdata->base + TRCACVRn(i));
+		state->trcacatr[i] = readl(drvdata->base + TRCACATRn(i));
+	}
+
+	/*
+	 * Data trace stream is architecturally prohibited for A profile cores
+	 * so we don't save (or later restore) trcdvcvr and trcdvcmr - As per
+	 * section 1.3.4 ("Possible functional configurations of an ETMv4 trace
+	 * unit") of ARM IHI 0064D.
+	 */
+
+	for (i = 0; i < drvdata->numcidc; i++)
+		state->trccidcvr[i] = readl(drvdata->base + TRCCIDCVRn(i));
+
+	for (i = 0; i < drvdata->numvmidc; i++)
+		state->trcvmidcvr[i] = readl(drvdata->base + TRCVMIDCVRn(i));
+
+	state->trccidcctlr0 = readl(drvdata->base + TRCCIDCCTLR0);
+	state->trccidcctlr1 = readl(drvdata->base + TRCCIDCCTLR1);
+
+	state->trcvmidcctlr0 = readl(drvdata->base + TRCVMIDCCTLR0);
+	state->trcvmidcctlr0 = readl(drvdata->base + TRCVMIDCCTLR1);
+
+	state->trcclaimset = readl(drvdata->base + TRCCLAIMCLR);
+
+	state->trcpdcr = readl(drvdata->base + TRCPDCR);
+
+	/* wait for TRCSTATR.IDLE to go up */
+	if (coresight_timeout(drvdata->base, TRCSTATR, TRCSTATR_IDLE_BIT, 1)) {
+		dev_err(etm_dev,
+			"timeout while waiting for Idle Trace Status\n");
+		etm4_os_unlock(drvdata);
+		ret = -EBUSY;
+		goto out;
+	}
+
+	drvdata->state_needs_restore = true;
+
+	/*
+	 * Power can be removed from the trace unit now. We do this to
+	 * potentially save power on systems that respect the TRCPDCR_PU
+	 * despite requesting software to save/restore state.
+	 */
+	writel_relaxed((state->trcpdcr & ~TRCPDCR_PU),
+			drvdata->base + TRCPDCR);
+
+out:
+	CS_LOCK(drvdata->base);
+	return ret;
+}
+
+static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
+{
+	int i;
+	struct etmv4_save_state *state = drvdata->save_state;
+
+	CS_UNLOCK(drvdata->base);
+
+	writel_relaxed(state->trcclaimset, drvdata->base + TRCCLAIMSET);
+
+	writel_relaxed(state->trcprgctlr, drvdata->base + TRCPRGCTLR);
+	writel_relaxed(state->trcprocselr, drvdata->base + TRCPROCSELR);
+	writel_relaxed(state->trcconfigr, drvdata->base + TRCCONFIGR);
+	writel_relaxed(state->trcauxctlr, drvdata->base + TRCAUXCTLR);
+	writel_relaxed(state->trceventctl0r, drvdata->base + TRCEVENTCTL0R);
+	writel_relaxed(state->trceventctl1r, drvdata->base + TRCEVENTCTL1R);
+	writel_relaxed(state->trcstallctlr, drvdata->base + TRCSTALLCTLR);
+	writel_relaxed(state->trctsctlr, drvdata->base + TRCTSCTLR);
+	writel_relaxed(state->trcsyncpr, drvdata->base + TRCSYNCPR);
+	writel_relaxed(state->trcccctlr, drvdata->base + TRCCCCTLR);
+	writel_relaxed(state->trcbbctlr, drvdata->base + TRCBBCTLR);
+	writel_relaxed(state->trctraceidr, drvdata->base + TRCTRACEIDR);
+	writel_relaxed(state->trcqctlr, drvdata->base + TRCQCTLR);
+
+	writel_relaxed(state->trcvictlr, drvdata->base + TRCVICTLR);
+	writel_relaxed(state->trcviiectlr, drvdata->base + TRCVIIECTLR);
+	writel_relaxed(state->trcvissctlr, drvdata->base + TRCVISSCTLR);
+	writel_relaxed(state->trcvipcssctlr, drvdata->base + TRCVIPCSSCTLR);
+	writel_relaxed(state->trcvdctlr, drvdata->base + TRCVDCTLR);
+	writel_relaxed(state->trcvdsacctlr, drvdata->base + TRCVDSACCTLR);
+	writel_relaxed(state->trcvdarcctlr, drvdata->base + TRCVDARCCTLR);
+
+	for (i = 0; i < drvdata->nrseqstate; i++)
+		writel_relaxed(state->trcseqevr[i],
+			       drvdata->base + TRCSEQEVRn(i));
+
+	writel_relaxed(state->trcseqrstevr, drvdata->base + TRCSEQRSTEVR);
+	writel_relaxed(state->trcseqstr, drvdata->base + TRCSEQSTR);
+	writel_relaxed(state->trcextinselr, drvdata->base + TRCEXTINSELR);
+
+	for (i = 0; i < drvdata->nr_cntr; i++) {
+		writel_relaxed(state->trccntrldvr[i],
+			       drvdata->base + TRCCNTRLDVRn(i));
+		writel_relaxed(state->trccntctlr[i],
+			       drvdata->base + TRCCNTCTLRn(i));
+		writel_relaxed(state->trccntvr[i],
+			       drvdata->base + TRCCNTVRn(i));
+	}
+
+	for (i = 0; i < drvdata->nr_resource * 2; i++)
+		writel_relaxed(state->trcrsctlr[i],
+			       drvdata->base + TRCRSCTLRn(i));
+
+	for (i = 0; i < drvdata->nr_ss_cmp; i++) {
+		writel_relaxed(state->trcssccr[i],
+			       drvdata->base + TRCSSCCRn(i));
+		writel_relaxed(state->trcsscsr[i],
+			       drvdata->base + TRCSSCSRn(i));
+		writel_relaxed(state->trcsspcicr[i],
+			       drvdata->base + TRCSSPCICRn(i));
+	}
+
+	for (i = 0; i < drvdata->nr_addr_cmp * 2; i++) {
+		writel_relaxed(state->trcacvr[i],
+			       drvdata->base + TRCACVRn(i));
+		writel_relaxed(state->trcacatr[i],
+			       drvdata->base + TRCACATRn(i));
+	}
+
+	for (i = 0; i < drvdata->numcidc; i++)
+		writel_relaxed(state->trccidcvr[i],
+			       drvdata->base + TRCCIDCVRn(i));
+
+	for (i = 0; i < drvdata->numvmidc; i++)
+		writel_relaxed(state->trcvmidcvr[i],
+			       drvdata->base + TRCVMIDCVRn(i));
+
+	writel_relaxed(state->trccidcctlr0, drvdata->base + TRCCIDCCTLR0);
+	writel_relaxed(state->trccidcctlr1, drvdata->base + TRCCIDCCTLR1);
+
+	writel_relaxed(state->trcvmidcctlr0, drvdata->base + TRCVMIDCCTLR0);
+	writel_relaxed(state->trcvmidcctlr0, drvdata->base + TRCVMIDCCTLR1);
+
+	writel_relaxed(state->trcclaimset, drvdata->base + TRCCLAIMSET);
+
+	writel_relaxed(state->trcpdcr, drvdata->base + TRCPDCR);
+
+	drvdata->state_needs_restore = false;
+
+	/*
+	 * As recommended by section 4.3.7 ("Synchronization when using the
+	 * memory-mapped interface") of ARM IHI 0064D
+	 */
+	dsb(sy);
+	isb();
+
+	/* Unlock the OS lock to re-enable trace and external debug access */
+	etm4_os_unlock(drvdata);
+	CS_LOCK(drvdata->base);
+}
+
+static int etm4_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
+			      void *v)
+{
+	struct etmv4_drvdata *drvdata;
+	unsigned int cpu = smp_processor_id();
+
+	if (!etmdrvdata[cpu])
+		return NOTIFY_OK;
+
+	drvdata = etmdrvdata[cpu];
+
+	if (!drvdata->save_state)
+		return NOTIFY_OK;
+
+	if (WARN_ON_ONCE(drvdata->cpu != cpu))
+		return NOTIFY_BAD;
+
+	switch (cmd) {
+	case CPU_PM_ENTER:
+		/* save the state if self-hosted coresight is in use */
+		if (local_read(&drvdata->mode))
+			if (etm4_cpu_save(drvdata))
+				return NOTIFY_BAD;
+		break;
+	case CPU_PM_EXIT:
+		/* fallthrough */
+	case CPU_PM_ENTER_FAILED:
+		if (drvdata->state_needs_restore)
+			etm4_cpu_restore(drvdata);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block etm4_cpu_pm_nb = {
+	.notifier_call = etm4_cpu_pm_notify,
+};
+
+static int etm4_cpu_pm_register(void)
+{
+	return cpu_pm_register_notifier(&etm4_cpu_pm_nb);
+}
+
+static void etm4_cpu_pm_unregister(void)
+{
+	cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
+}
+#else
+static int etm4_cpu_pm_register(void) { return 0; }
+static void etm4_cpu_pm_unregister(void) { }
+#endif
+
 static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 {
 	int ret;
@@ -1101,6 +1402,17 @@  static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 
 	dev_set_drvdata(dev, drvdata);
 
+	if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE)
+		pm_save_enable = coresight_loses_context_with_cpu(dev) ?
+			       PARAM_PM_SAVE_SELF_HOSTED : PARAM_PM_SAVE_NEVER;
+
+	if (pm_save_enable != PARAM_PM_SAVE_NEVER) {
+		drvdata->save_state = devm_kmalloc(dev,
+				sizeof(struct etmv4_save_state), GFP_KERNEL);
+		if (!drvdata->save_state)
+			return -ENOMEM;
+	}
+
 	/* Validity for the resource is already checked by the AMBA core */
 	base = devm_ioremap_resource(dev, res);
 	if (IS_ERR(base))
@@ -1135,6 +1447,10 @@  static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 		if (ret < 0)
 			goto err_arch_supported;
 		hp_online = ret;
+
+		ret = etm4_cpu_pm_register();
+		if (ret)
+			goto err_arch_supported;
 	}
 
 	cpus_read_unlock();
@@ -1185,6 +1501,8 @@  static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 
 err_arch_supported:
 	if (--etm4_count == 0) {
+		etm4_cpu_pm_unregister();
+
 		cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
 		if (hp_online)
 			cpuhp_remove_state_nocalls(hp_online);
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 4523f10ddd0f..546d790cb01b 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -175,6 +175,7 @@ 
 					 ETM_MODE_EXCL_USER)
 
 #define TRCSTATR_IDLE_BIT		0
+#define TRCSTATR_PMSTABLE_BIT		1
 #define ETM_DEFAULT_ADDR_COMP		0
 
 /* PowerDown Control Register bits */
@@ -281,6 +282,65 @@  struct etmv4_config {
 	u32				ext_inp;
 };
 
+/**
+ * struct etm4_save_state - state to be preserved when ETM is without power
+ */
+struct etmv4_save_state {
+	u32	trcprgctlr;
+	u32	trcprocselr;
+	u32	trcconfigr;
+	u32	trcauxctlr;
+	u32	trceventctl0r;
+	u32	trceventctl1r;
+	u32	trcstallctlr;
+	u32	trctsctlr;
+	u32	trcsyncpr;
+	u32	trcccctlr;
+	u32	trcbbctlr;
+	u32	trctraceidr;
+	u32	trcqctlr;
+
+	u32	trcvictlr;
+	u32	trcviiectlr;
+	u32	trcvissctlr;
+	u32	trcvipcssctlr;
+	u32	trcvdctlr;
+	u32	trcvdsacctlr;
+	u32	trcvdarcctlr;
+
+	u32	trcseqevr[ETM_MAX_SEQ_STATES];
+	u32	trcseqrstevr;
+	u32	trcseqstr;
+	u32	trcextinselr;
+	u32	trccntrldvr[ETMv4_MAX_CNTR];
+	u32	trccntctlr[ETMv4_MAX_CNTR];
+	u32	trccntvr[ETMv4_MAX_CNTR];
+
+	u32	trcrsctlr[ETM_MAX_RES_SEL * 2];
+
+	u32	trcssccr[ETM_MAX_SS_CMP];
+	u32	trcsscsr[ETM_MAX_SS_CMP];
+	u32	trcsspcicr[ETM_MAX_SS_CMP];
+
+	u64	trcacvr[ETM_MAX_SINGLE_ADDR_CMP];
+	u64	trcacatr[ETM_MAX_SINGLE_ADDR_CMP];
+	u64	trccidcvr[ETMv4_MAX_CTXID_CMP];
+	u32	trcvmidcvr[ETM_MAX_VMID_CMP];
+	u32	trccidcctlr0;
+	u32	trccidcctlr1;
+	u32	trcvmidcctlr0;
+	u32	trcvmidcctlr1;
+
+	u32	trcclaimset;
+
+	u32	cntr_val[ETMv4_MAX_CNTR];
+	u32	seq_state;
+	u32	vinst_ctrl;
+	u32	ss_status[ETM_MAX_SS_CMP];
+
+	u32	trcpdcr;
+};
+
 /**
  * struct etm4_drvdata - specifics associated to an ETM component
  * @base:       Memory mapped base address for this component.
@@ -336,6 +396,8 @@  struct etmv4_config {
  * @atbtrig:	If the implementation can support ATB triggers
  * @lpoverride:	If the implementation can support low-power state over.
  * @config:	structure holding configuration parameters.
+ * @save_state:	State to be preserved across power loss
+ * @state_needs_restore: True when there is context to restore after PM exit
  */
 struct etmv4_drvdata {
 	void __iomem			*base;
@@ -381,6 +443,8 @@  struct etmv4_drvdata {
 	bool				atbtrig;
 	bool				lpoverride;
 	struct etmv4_config		config;
+	struct etmv4_save_state		*save_state;
+	bool				state_needs_restore;
 };
 
 /* Address comparator access types */
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 55db77f6410b..c2a48a4e73ea 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -1310,6 +1310,12 @@  static inline int coresight_search_device_idx(struct coresight_dev_list *dict,
 	return -ENOENT;
 }
 
+bool coresight_loses_context_with_cpu(struct device *dev)
+{
+	return fwnode_property_present(dev_fwnode(dev),
+				       "arm,coresight-loses-context-with-cpu");
+}
+
 /*
  * coresight_alloc_device_name - Get an index for a given device in the
  * device index list specific to a driver. An index is allocated for a
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index a2b68823717b..44e552de419c 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -285,6 +285,8 @@  extern void coresight_disclaim_device(void __iomem *base);
 extern void coresight_disclaim_device_unlocked(void __iomem *base);
 extern char *coresight_alloc_device_name(struct coresight_dev_list *devs,
 					 struct device *dev);
+
+extern bool coresight_loses_context_with_cpu(struct device *dev);
 #else
 static inline struct coresight_device *
 coresight_register(struct coresight_desc *desc) { return NULL; }
@@ -307,6 +309,10 @@  static inline int coresight_claim_device(void __iomem *base)
 static inline void coresight_disclaim_device(void __iomem *base) {}
 static inline void coresight_disclaim_device_unlocked(void __iomem *base) {}
 
+static inline bool coresight_loses_context_with_cpu(struct device *dev)
+{
+	return false;
+}
 #endif
 
 extern int coresight_get_cpu(struct device *dev);