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@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; }