[PATCH v2] coresight: etm4x: add CPU hotplug support for probing
Tamas Zsoldos
tamas.zsoldos at arm.com
Tue Jul 5 07:59:35 PDT 2022
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: Tamas Zsoldos <tamas.zsoldos at arm.com>
---
Changes from v1 (all suggested by Suzuki):
1. Expanded commit message.
2. The delayed probe now uses etm4_init_arg.
3. Reuses etm4_online_cpu() instead of installing own cpuhp callback.
4. Changed guard condition in etm4_remove_dev().
---
.../coresight/coresight-etm4x-core.c | 153 +++++++++++++-----
1 file changed, 113 insertions(+), 40 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 87299e99dabb..c39d9055b22c 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -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.
*
@@ -1071,7 +1074,7 @@ 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;
/*
@@ -1514,7 +1517,7 @@ 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);
@@ -1890,48 +1893,20 @@ 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;
@@ -2002,6 +1977,68 @@ 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;
@@ -2040,6 +2077,35 @@ 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 */
@@ -2054,16 +2120,20 @@ 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
@@ -2071,12 +2141,15 @@ 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();
- cscfg_unregister_csdev(drvdata->csdev);
- coresight_unregister(drvdata->csdev);
+ if (!had_delayed_probe) {
+ etm_perf_symlink(drvdata->csdev, false);
+ cscfg_unregister_csdev(drvdata->csdev);
+ coresight_unregister(drvdata->csdev);
+ }
return 0;
}
--
2.17.1
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