Re: [PATCH v5 1/3] coresight: etm4x: save/restore state across CPU low power states

Hi Andrew,

On Fri, Aug 16, 2019 at 04:46:13PM +0100, Andrew Murray wrote:

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

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(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index a128b5063f46..35a524eec36d 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)) {
  

Indentation problems

• 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 0;
  

• 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:

Implicit fallthroughs are coming to an end. Please add a /* fallthrough */

• case CPU_PM_ENTER_FAILED:

• /* trcclaimset is set when there is state to restore */
  

As far as I can tell the above comment doesn't apply anymore.

• 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 6453c67a4d01..e6ca899fea4e 100644 --- a/drivers/hwtracing/coresight/coresight.c +++ b/drivers/hwtracing/coresight/coresight.c @@ -1308,6 +1308,12 @@ 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); -- 2.21.0