Re: [PATCH v2 2/2] coresight: cti: Add CPU idle pm notifer to CTI devices.

On Mon, May 04, 2020 at 05:15:30PM +0100, Mike Leach wrote:

Adds a notify callback for CPU PM events to the CTI driver - for CPU bound CTI devices.

Signed-off-by: Mike Leach mike.leach@linaro.org

drivers/hwtracing/coresight/coresight-cti.c | 82 +++++++++++++++++++++ 1 file changed, 82 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 9af66719ae5b..0f0c14528701 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -8,6 +8,7 @@ #include <linux/atomic.h> #include <linux/bits.h> #include <linux/coresight.h> +#include <linux/cpu_pm.h> #include <linux/device.h> #include <linux/io.h> #include <linux/kernel.h> @@ -655,6 +656,84 @@ 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;
• unsigned int cpu = smp_processor_id();
• int notify_res = NOTIFY_OK;
• if (!cti_cpu_drvdata[cpu])

• return NOTIFY_OK;
  

• drvdata = cti_cpu_drvdata[cpu];
• if (WARN_ON_ONCE(drvdata->ctidev.cpu != cpu))

• return NOTIFY_BAD;
  

• spin_lock(&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(drvdata->base);
  

• break;
  

• case CPU_PM_ENTER_FAILED:

• drvdata->config.hw_powered = true;
  

• if (drvdata->config.hw_enabled) {
  

• 	if (coresight_claim_device(drvdata->base))
  

• 		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 (atomic_read(&drvdata->config.enable_req_count)) {
  

• 	/* check we can claim the device as we re-power */
  

• 	if (coresight_claim_device(drvdata->base))
  

• 		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:

• spin_unlock(&drvdata->spinlock);
• return notify_res;

+}

+static struct notifier_block cti_cpu_pm_nb = {

• .notifier_call = cti_cpu_pm_notify,

+};

+static int cti_cpu_pm_register(void) +{

• if (IS_ENABLED(CONFIG_CPU_PM))

• return cpu_pm_register_notifier(&cti_cpu_pm_nb);
  

Looking further into function cpu_pm_register_notifier(), it simply returns '0' if CONFIG_CPU_PM is not defined. As such cpu_pm_register_notifier() can be called directly from cti_probe(). The same applies to cpu_pm_unregister_notifier().

• return 0;

+}

+static void cti_cpu_pm_unregister(void) +{

• if (IS_ENABLED(CONFIG_CPU_PM))

• cpu_pm_unregister_notifier(&cti_cpu_pm_nb);
  

+}

/* CPU HP handlers */ static int cti_starting_cpu(unsigned int cpu) { @@ -686,6 +765,8 @@ static void cti_pm_release(struct cti_drvdata *drvdata) { if (drvdata->ctidev.cpu >= 0) { if (--nr_cti_cpu == 0) {

• 	cti_cpu_pm_unregister();
  

• cpuhp_remove_state_nocalls(
  	CPUHP_AP_ARM_CORESIGHT_CTI_STARTING);
  

  }

@@ -814,6 +895,7 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id) "arm/coresight_cti:starting", cti_starting_cpu, cti_dying_cpu);

• 	ret = cti_cpu_pm_register();
  

This should be one only if cpuhp_remove_state_nocalls() hasn't returned an error.

Otherwise this looks good.

Thanks, Mathieu

	cpus_read_unlock();
	if (ret)
		goto err_out;

-- 2.17.1