Commit 3c728e07 authored by Tamas Zsoldos's avatar Tamas Zsoldos Committed by Suzuki K Poulose
Browse files

coresight: etm4x: add CPU hotplug support for probing 



etm4x devices cannot be successfully probed when their CPU is offline.
For example, when booting with maxcpus=n, ETM probing will fail on
CPUs >n, and the probing won't be reattempted once the CPUs come
online. This will leave those CPUs unable to make use of ETM.

This change adds a mechanism to delay the probing if the corresponding
CPU is offline, and to try it again when the CPU comes online.

Signed-off-by: default avatarTamas Zsoldos <tamas.zsoldos@arm.com>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220705145935.24679-1-tamas.zsoldos@arm.com
parent 30a0b95b

drivers/hwtracing/coresight/coresight-etm4x-core.c

+113 −40
Original line number Diff line number Diff line
@@ -66,10 +66,13 @@ static enum cpuhp_state hp_online; 


struct etm4_init_arg {

	unsigned int		pid;

	struct etmv4_drvdata	*drvdata;

	struct device		*dev;

	struct csdev_access	*csa;

};



static DEFINE_PER_CPU(struct etm4_init_arg *, delayed_probe);

static int etm4_probe_cpu(unsigned int cpu);



/*

 * Check if TRCSSPCICRn(i) is implemented for a given instance.

 *
@@ -1085,7 +1088,7 @@ static void etm4_init_arch_data(void *info) 
	struct csdev_access *csa;

	int i;



	drvdata = init_arg->drvdata;

	drvdata = dev_get_drvdata(init_arg->dev);

	csa = init_arg->csa;



	/*
@@ -1528,7 +1531,7 @@ void etm4_config_trace_mode(struct etmv4_config *config) 
static int etm4_online_cpu(unsigned int cpu)

{

	if (!etmdrvdata[cpu])

		return 0;

		return etm4_probe_cpu(cpu);



	if (etmdrvdata[cpu]->boot_enable && !etmdrvdata[cpu]->sticky_enable)

		coresight_enable(etmdrvdata[cpu]->csdev);
@@ -1904,48 +1907,20 @@ static void etm4_pm_clear(void) 
	}

}



static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)

static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg)

{

	int ret;

	struct coresight_platform_data *pdata = NULL;

	struct etmv4_drvdata *drvdata;

	struct device *dev = init_arg->dev;

	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);

	struct coresight_desc desc = { 0 };

	struct etm4_init_arg init_arg = { 0 };

	u8 major, minor;

	char *type_name;



	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);

	if (!drvdata)

		return -ENOMEM;



	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;

	}



	drvdata->base = base;



	spin_lock_init(&drvdata->spinlock);



	drvdata->cpu = coresight_get_cpu(dev);

	if (drvdata->cpu < 0)

		return drvdata->cpu;



	init_arg.drvdata = drvdata;

	init_arg.csa = &desc.access;

	init_arg.pid = etm_pid;

		return -EINVAL;



	if (smp_call_function_single(drvdata->cpu,

				etm4_init_arch_data,  &init_arg, 1))

		dev_err(dev, "ETM arch init failed\n");

	desc.access = *init_arg->csa;



	if (!drvdata->arch)

		return -EINVAL;
@@ -2016,6 +1991,68 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid) 
	return 0;

}



static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)

{

	struct etmv4_drvdata *drvdata;

	struct csdev_access access = { 0 };

	struct etm4_init_arg init_arg = { 0 };

	struct etm4_init_arg *delayed;



	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);

	if (!drvdata)

		return -ENOMEM;



	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;

	}



	drvdata->base = base;



	spin_lock_init(&drvdata->spinlock);



	drvdata->cpu = coresight_get_cpu(dev);

	if (drvdata->cpu < 0)

		return drvdata->cpu;



	init_arg.dev = dev;

	init_arg.csa = &access;

	init_arg.pid = etm_pid;



	/*

	 * Serialize against CPUHP callbacks to avoid race condition

	 * between the smp call and saving the delayed probe.

	 */

	cpus_read_lock();

	if (smp_call_function_single(drvdata->cpu,

				etm4_init_arch_data,  &init_arg, 1)) {

		/* The CPU was offline, try again once it comes online. */

		delayed = devm_kmalloc(dev, sizeof(*delayed), GFP_KERNEL);

		if (!delayed) {

			cpus_read_unlock();

			return -ENOMEM;

		}



		*delayed = init_arg;



		per_cpu(delayed_probe, drvdata->cpu) = delayed;



		cpus_read_unlock();

		return 0;

	}

	cpus_read_unlock();



	return etm4_add_coresight_dev(&init_arg);

}



static int etm4_probe_amba(struct amba_device *adev, const struct amba_id *id)

{

	void __iomem *base;
@@ -2054,6 +2091,35 @@ static int etm4_probe_platform_dev(struct platform_device *pdev) 
	return ret;

}



static int etm4_probe_cpu(unsigned int cpu)

{

	int ret;

	struct etm4_init_arg init_arg;

	struct csdev_access access = { 0 };

	struct etm4_init_arg *iap = *this_cpu_ptr(&delayed_probe);



	if (!iap)

		return 0;



	init_arg = *iap;

	devm_kfree(init_arg.dev, iap);

	*this_cpu_ptr(&delayed_probe) = NULL;



	ret = pm_runtime_resume_and_get(init_arg.dev);

	if (ret < 0) {

		dev_err(init_arg.dev, "Failed to get PM runtime!\n");

		return 0;

	}



	init_arg.csa = &access;

	etm4_init_arch_data(&init_arg);



	etm4_add_coresight_dev(&init_arg);



	pm_runtime_put(init_arg.dev);

	return 0;

}



static struct amba_cs_uci_id uci_id_etm4[] = {

	{

		/*  ETMv4 UCI data */
@@ -2068,16 +2134,20 @@ static void clear_etmdrvdata(void *info) 
	int cpu = *(int *)info;



	etmdrvdata[cpu] = NULL;

	per_cpu(delayed_probe, cpu) = NULL;

}



static int __exit etm4_remove_dev(struct etmv4_drvdata *drvdata)

{

	etm_perf_symlink(drvdata->csdev, false);

	bool had_delayed_probe;

	/*

	 * Taking hotplug lock here to avoid racing between etm4_remove_dev()

	 * and CPU hotplug call backs.

	 */

	cpus_read_lock();



	had_delayed_probe = per_cpu(delayed_probe, drvdata->cpu);



	/*

	 * The readers for etmdrvdata[] are CPU hotplug call backs

	 * and PM notification call backs. Change etmdrvdata[i] on
@@ -2085,12 +2155,15 @@ static int __exit etm4_remove_dev(struct etmv4_drvdata *drvdata) 
	 * inside one call back function.

	 */

	if (smp_call_function_single(drvdata->cpu, clear_etmdrvdata, &drvdata->cpu, 1))

		etmdrvdata[drvdata->cpu] = NULL;

		clear_etmdrvdata(&drvdata->cpu);



	cpus_read_unlock();



	if (!had_delayed_probe) {

		etm_perf_symlink(drvdata->csdev, false);

		cscfg_unregister_csdev(drvdata->csdev);

		coresight_unregister(drvdata->csdev);

	}



	return 0;

}