[PATCH 4/8] coresight: cti: Remove CPU power management code
Mike Leach
Mike.Leach at arm.com
Fri Feb 20 05:19:36 PST 2026
> -----Original Message-----
> From: Leo Yan <leo.yan at arm.com>
> Sent: Monday, February 9, 2026 6:01 PM
> To: Suzuki Poulose <Suzuki.Poulose at arm.com>; Mike Leach
> <Mike.Leach at arm.com>; James Clark <james.clark at linaro.org>; Alexander
> Shishkin <alexander.shishkin at linux.intel.com>; Greg Kroah-Hartman
> <gregkh at linuxfoundation.org>; Mathieu Poirier
> <mathieu.poirier at linaro.org>; Tingwei Zhang <quic_tingwei at quicinc.com>;
> Yingchao Deng <yingchao.deng at oss.qualcomm.com>; Jie Gan
> <jie.gan at oss.qualcomm.com>
> Cc: coresight at lists.linaro.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; Leo Yan <Leo.Yan at arm.com>
> Subject: [PATCH 4/8] coresight: cti: Remove CPU power management code
>
> According Arm ARM, the CTI ASICCTL register:
>
> "It is IMPLEMENTATION DEFINED whether ASICCTL is implemented in the
> Core power domain or in the Debug power domain."
>
> This is the only CTI register that may reside in the core power domain.
> However, it has been confirmed that Arm designed CTIs place ASICCTL in
> the debug power domain. Furthermore, ASICCTL is implemented only when
> CTIDEVID.EXTMUXNUM is non-zero, which is a rare case for CPU CTIs.
>
> For these reasons, it is safe to conclude that all CTI registers are not
> located in the CPU power domain. Therefore, the CTI driver does not need
> CPU power management.
>
> This commit removes the CPU power management from CTI driver.
>
> Signed-off-by: Leo Yan <leo.yan at arm.com>
> ---
> drivers/hwtracing/coresight/coresight-cti-core.c | 186 +----------------------
> 1 file changed, 3 insertions(+), 183 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c
> b/drivers/hwtracing/coresight/coresight-cti-core.c
> index
> 1950e9b757ae4879a2671ddaf5675c54aa7956d5..3becef607e5ec5225cb6f
> d616da804903651fdf1 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> @@ -42,12 +42,6 @@ static DEFINE_MUTEX(ect_mutex);
> #define csdev_to_cti_drvdata(csdev) \
> dev_get_drvdata(csdev->dev.parent)
>
> -/* power management handling */
> -static int nr_cti_cpu;
> -
> -/* quick lookup list for CPU bound CTIs when power handling */
> -static struct cti_drvdata *cti_cpu_drvdata[NR_CPUS];
> -
> /*
> * CTI naming. CTI bound to cores will have the name cti_cpu<N> where
> * N is the CPU ID. System CTIs will have the name cti_sys<I> where I
> @@ -113,28 +107,6 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
> return 0;
> }
>
> -/* re-enable CTI on CPU when using CPU hotplug */
> -static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
> -{
> - struct cti_config *config = &drvdata->config;
> -
> - guard(raw_spinlock_irqsave)(&drvdata->spinlock);
> -
> - config->hw_powered = true;
> -
> - /* no need to do anything if no enable request */
> - if (!drvdata->config.enable_req_count)
> - return;
> -
> - /* try to claim the device */
> - if (coresight_claim_device(drvdata->csdev))
> - return;
> -
> - cti_write_all_hw_regs(drvdata);
> - config->hw_enabled = true;
> - return;
> -}
> -
> /* disable hardware */
> static int cti_disable_hw(struct cti_drvdata *drvdata)
> {
> @@ -652,146 +624,6 @@ static void cti_remove_conn_xrefs(struct
> cti_drvdata *drvdata)
> }
> }
>
> -/** cti PM callbacks **/
> -static int cti_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
> - void *v)
> -{
> - struct cti_drvdata *drvdata;
> - struct coresight_device *csdev;
> - unsigned int cpu = smp_processor_id();
> - int notify_res = NOTIFY_OK;
> -
> - if (!cti_cpu_drvdata[cpu])
> - return NOTIFY_OK;
> -
> - drvdata = cti_cpu_drvdata[cpu];
> - csdev = drvdata->csdev;
> -
> - if (WARN_ON_ONCE(drvdata->ctidev.cpu != cpu))
> - return NOTIFY_BAD;
> -
> - guard(raw_spinlock_irqsave)(&drvdata->spinlock);
> -
> - switch (cmd) {
> - case CPU_PM_ENTER:
> - /* CTI regs all static - we have a copy & nothing to save */
> - drvdata->config.hw_powered = false;
> - if (drvdata->config.hw_enabled)
> - coresight_disclaim_device(csdev);
> - break;
> -
> - case CPU_PM_ENTER_FAILED:
> - drvdata->config.hw_powered = true;
> - if (drvdata->config.hw_enabled) {
> - if (coresight_claim_device(csdev))
> - drvdata->config.hw_enabled = false;
> - }
> - break;
> -
> - case CPU_PM_EXIT:
> - /* write hardware registers to re-enable. */
> - drvdata->config.hw_powered = true;
> - drvdata->config.hw_enabled = false;
> -
> - /* check enable reference count to enable HW */
> - if (drvdata->config.enable_req_count) {
> - /* check we can claim the device as we re-power */
> - if (coresight_claim_device(csdev))
> - goto cti_notify_exit;
> -
> - drvdata->config.hw_enabled = true;
> - cti_write_all_hw_regs(drvdata);
> - }
> - break;
> -
> - default:
> - notify_res = NOTIFY_DONE;
> - break;
> - }
> -
> -cti_notify_exit:
> - return notify_res;
> -}
> -
> -static struct notifier_block cti_cpu_pm_nb = {
> - .notifier_call = cti_cpu_pm_notify,
> -};
> -
> -/* CPU HP handlers */
> -static int cti_starting_cpu(unsigned int cpu)
> -{
> - struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
> -
> - if (!drvdata)
> - return 0;
> -
> - cti_cpuhp_enable_hw(drvdata);
> - return 0;
> -}
> -
> -static int cti_dying_cpu(unsigned int cpu)
> -{
> - struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
> -
> - if (!drvdata)
> - return 0;
> -
> - guard(raw_spinlock_irqsave)(&drvdata->spinlock);
> -
> - drvdata->config.hw_powered = false;
> - if (drvdata->config.hw_enabled)
> - coresight_disclaim_device(drvdata->csdev);
> -
> - return 0;
> -}
> -
> -static int cti_pm_setup(struct cti_drvdata *drvdata)
> -{
> - int ret;
> -
> - if (drvdata->ctidev.cpu == -1)
> - return 0;
> -
> - if (nr_cti_cpu)
> - goto done;
> -
> - cpus_read_lock();
> - ret = cpuhp_setup_state_nocalls_cpuslocked(
> - CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
> - "arm/coresight_cti:starting",
> - cti_starting_cpu, cti_dying_cpu);
> - if (ret) {
> - cpus_read_unlock();
> - return ret;
> - }
> -
> - ret = cpu_pm_register_notifier(&cti_cpu_pm_nb);
> - cpus_read_unlock();
> - if (ret) {
> -
> cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_CTI_STA
> RTING);
> - return ret;
> - }
> -
> -done:
> - nr_cti_cpu++;
> - cti_cpu_drvdata[drvdata->ctidev.cpu] = drvdata;
> -
> - return 0;
> -}
> -
> -/* release PM registrations */
> -static void cti_pm_release(struct cti_drvdata *drvdata)
> -{
> - if (drvdata->ctidev.cpu == -1)
> - return;
> -
> - cti_cpu_drvdata[drvdata->ctidev.cpu] = NULL;
> - if (--nr_cti_cpu == 0) {
> - cpu_pm_unregister_notifier(&cti_cpu_pm_nb);
> -
> cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_CTI_STA
> RTING);
> - }
> -}
> -
> /** cti ect operations **/
> int cti_enable(struct coresight_device *csdev, enum cs_mode mode,
> struct coresight_path *path)
> @@ -827,7 +659,6 @@ static void cti_device_release(struct device *dev)
> struct cti_drvdata *ect_item, *ect_tmp;
>
> mutex_lock(&ect_mutex);
> - cti_pm_release(drvdata);
>
> /* remove from the list */
> list_for_each_entry_safe(ect_item, ect_tmp, &ect_net, node) {
> @@ -906,17 +737,12 @@ static int cti_probe(struct amba_device *adev,
> const struct amba_id *id)
> if (!cti_desc.name)
> return -ENOMEM;
>
> - /* setup CPU power management handling for CPU bound CTI
> devices. */
> - ret = cti_pm_setup(drvdata);
> - if (ret)
> - return ret;
> -
> /* create dynamic attributes for connections */
> ret = cti_create_cons_sysfs(dev, drvdata);
> if (ret) {
> dev_err(dev, "%s: create dynamic sysfs entries failed\n",
> cti_desc.name);
> - goto pm_release;
> + return ret;
> }
>
> /* set up coresight component description */
> @@ -929,10 +755,8 @@ static int cti_probe(struct amba_device *adev, const
> struct amba_id *id)
>
> coresight_clear_self_claim_tag(&cti_desc.access);
> drvdata->csdev = coresight_register(&cti_desc);
> - if (IS_ERR(drvdata->csdev)) {
> - ret = PTR_ERR(drvdata->csdev);
> - goto pm_release;
> - }
> + if (IS_ERR(drvdata->csdev))
> + return PTR_ERR(drvdata->csdev);
>
> /* add to list of CTI devices */
> mutex_lock(&ect_mutex);
> @@ -949,10 +773,6 @@ static int cti_probe(struct amba_device *adev, const
> struct amba_id *id)
> pm_runtime_put(&adev->dev);
> dev_info(&drvdata->csdev->dev, "CTI initialized\n");
> return 0;
> -
> -pm_release:
> - cti_pm_release(drvdata);
> - return ret;
> }
>
> static struct amba_cs_uci_id uci_id_cti[] = {
>
> --
> 2.34.1
Reviewed-by: Mike Leach <mike.leach at arm.com>
More information about the linux-arm-kernel
mailing list