RE: [PATCH v2 1/4] coresight: syscfg: Fail to enable a configuration not loaded on the device

Hi,

-----Original Message----- From: Amir Ayupov aaupov@fb.com Sent: Tuesday, October 13, 2026 12:05 AM To: James Clark james.clark@linaro.org; Leo Yan Leo.Yan@arm.com; Suzuki Poulose Suzuki.Poulose@arm.com; Mike Leach Mike.Leach@arm.com; Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org; Jonathan Corbet corbet@lwn.net; Mathieu Poirier mathieu.poirier@linaro.org; Randy Dunlap rdunlap@infradead.org; Shuah Khan skhan@linuxfoundation.org; coresight@lists.linaro.org; linux-arm-kernel@lists.infradead.org; linux- doc@vger.kernel.org; linux-kernel@vger.kernel.org Subject: [PATCH v2 1/4] coresight: syscfg: Fail to enable a configuration not loaded on the device

cscfg_csdev_enable_active_config() looks up the selected configuration in the device's loaded configurations, and returns success when it is not there. A configuration is only loaded on devices that match at least one of its features, so a perf session or sysfs enable that selects it on any other device runs without the configuration, with no error.

Return -EINVAL instead, so enabling the source fails on that device. The function is only called with a non-zero configuration hash, so sources enabled without a configuration are unaffected.

If you look at the original comments - the idea of this function is to enable a configuration on a device if it is present on that device. Not enabling a configuration is _not_ an error. This is a generic function that can cover multiple classes of coresight device.

Moving forwards matching configurations to devices can omit certain devices from the configuration.

For example, a system will have many CTIs, but we may only want to use a specific one or two - possibly to connect etm external outputs to trigger a PE interrupt. Thus the remaining CTIs would not be active in this configuration.

This conflicts with your purpose which I assume is to prevent perf from using ETM sources that cannot load the required configuration.

I think what is actually needed is a "can_activate" function to be run on the ETM/ETE sources at etm_setup_aux time so that none compliant devices can be filtered out of the active cpu mask at that point.

Regards

Mike

Fixes: f8cce2ff3c04 ("coresight: syscfg: Add API to activate and enable configurations") Assisted-by: Devmate:Opus-5.5 Signed-off-by: Amir Ayupov aaupov@fb.com

---

.../hwtracing/coresight/coresight-syscfg.c | 53 ++++++++++--------- 1 file changed, 28 insertions(+), 25 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 2bfdd7b45e49c..a816c22c87bc8 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -1088,36 +1088,39 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev, raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);

/*

• * If found, attempt to enable
  

• * The configuration is active but not loaded on this device, because
  

• * none of its features match the device. Fail rather than trace
  

• * without it.
  

  */

• if (config_csdev_active) {

• if (!config_csdev_active)

• return -EINVAL;
  

• /*

• * Call the generic routine that will program up the internal
  

• * driver structures prior to programming up the hardware.
  

• * This routine takes the driver spinlock saved in the configs.
  

• */
  

• err = cscfg_csdev_enable_config(config_csdev_active, preset);
• if (!err) { /*

•  * Call the generic routine that will program up the internal
  

•  * driver structures prior to programming up the hardware.
  

•  * This routine takes the driver spinlock saved in the configs.
  

•  * Successful programming. Check the active_cscfg_ctxt
  

•  * pointer to ensure no pre-emption disabled it via
  

•  * cscfg_csdev_disable_active_config() before
  

•  * we could start.
  

•  *
  

•  * Set enabled if OK, err if not.
  

  */

• err = cscfg_csdev_enable_config(config_csdev_active, preset);
  

• if (!err) {
  

• 	/*
  

• 	 * Successful programming. Check the
  

active_cscfg_ctxt

• 	 * pointer to ensure no pre-emption disabled it via
  

• 	 * cscfg_csdev_disable_active_config() before
  

• 	 * we could start.
  

• 	 *
  

• 	 * Set enabled if OK, err if not.
  

• 	 */
  

• 	raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock,
  

flags);

• 	if (csdev->active_cscfg_ctxt)
  

• 		config_csdev_active->enabled = true;
  

• 	else
  

• 		err = -EBUSY;
  

• 	raw_spin_unlock_irqrestore(&csdev-
  

...

cscfg_csdev_lock, flags);

• }
  

• if (err)
  

• 	cscfg_config_desc_put(config_desc);
  

• raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
  

• if (csdev->active_cscfg_ctxt)
  

• 	config_csdev_active->enabled = true;
  

• else
  

• 	err = -EBUSY;
  

• raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
  

  }

• if (err)

• cscfg_config_desc_put(config_desc);
  

• return err;

} EXPORT_SYMBOL_GPL(cscfg_csdev_enable_active_config); -- 2.52.0