Re: [PATCH v2 4/8] coresight: Add claim tag warnings and debug messages

On Tue, Mar 18, 2025 at 04:21:58PM +0000, James Clark wrote:

Add a dev_dbg() message so that external debugger conflicts are more visible. There are multiple reasons for -EBUSY so a message for this particular one could be helpful. Add errors for and enumerate all the other cases that are impossible.

Signed-off-by: James Clark james.clark@linaro.org

Reviewed-by: Leo Yan leo.yan@arm.com

---

drivers/hwtracing/coresight/coresight-core.c | 51 +++++++++++++++++----------- drivers/hwtracing/coresight/coresight-priv.h | 5 ++- 2 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index e39043a9551f..5f08845faf0d 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -135,16 +135,6 @@ static inline u32 coresight_read_claim_tags(struct coresight_device *csdev) csdev_access_relaxed_read32(&csdev->access, CORESIGHT_CLAIMCLR)); } -static inline bool coresight_is_claimed_self_hosted(struct coresight_device *csdev) -{

• return coresight_read_claim_tags(csdev) == CORESIGHT_CLAIM_SELF_HOSTED;

-}

-static inline bool coresight_is_claimed_any(struct coresight_device *csdev) -{

• return coresight_read_claim_tags(csdev) != 0;

-}

static inline void coresight_set_self_claim_tag(struct coresight_device *csdev) { csdev_access_relaxed_write32(&csdev->access, CORESIGHT_CLAIM_SELF_HOSTED, @@ -180,18 +170,41 @@ EXPORT_SYMBOL_GPL(coresight_clear_self_claim_tag_unlocked); */ int coresight_claim_device_unlocked(struct coresight_device *csdev) {

• int tag;
• struct csdev_access *csa;
• if (WARN_ON(!csdev)) return -EINVAL;

• if (coresight_is_claimed_any(csdev))

• csa = &csdev->access;
• tag = coresight_read_claim_tags(csdev);
• switch (tag) {
• case CORESIGHT_CLAIM_FREE:

• coresight_set_self_claim_tag(csdev);
  

• if (coresight_read_claim_tags(csdev) == CORESIGHT_CLAIM_SELF_HOSTED)
  

• 	return 0;
  

• /* There was a race setting the tag, clean up and fail */
  

• coresight_clear_self_claim_tag_unlocked(csa);
  

• dev_dbg(&csdev->dev, "Busy: Couldn't set self claim tag");
  

  return -EBUSY;

• coresight_set_self_claim_tag(csdev);
• if (coresight_is_claimed_self_hosted(csdev))

• return 0;
  

• /* There was a race setting the tag, clean up and fail */
• coresight_clear_self_claim_tag_unlocked(&csdev->access);
• return -EBUSY;

• case CORESIGHT_CLAIM_EXTERNAL:

• /* External debug is an expected state, so log and report BUSY */
  

• dev_dbg(&csdev->dev, "Busy: Claimed by external debugger");
  

• return -EBUSY;
  

• default:
• case CORESIGHT_CLAIM_SELF_HOSTED:
• case CORESIGHT_CLAIM_INVALID:

• /*
  

•  * Warn here because we clear a lingering self hosted tag
  

•  * on probe, so other tag combinations are impossible.
  

•  */
  

• dev_err_once(&csdev->dev, "Invalid claim tag state: %x", tag);
  

• return -EBUSY;
  

• }

} EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked); @@ -220,7 +233,7 @@ void coresight_disclaim_device_unlocked(struct coresight_device *csdev) if (WARN_ON(!csdev)) return;

• if (coresight_is_claimed_self_hosted(csdev))

• if (coresight_read_claim_tags(csdev) == CORESIGHT_CLAIM_SELF_HOSTED) coresight_clear_self_claim_tag_unlocked(&csdev->access); else /*

@@ -228,7 +241,7 @@ void coresight_disclaim_device_unlocked(struct coresight_device *csdev) * and has manipulated it. Or something else has seriously * gone wrong in our driver. */

• WARN_ON_ONCE(1);
  

• dev_WARN_ONCE(&csdev->dev, 1, "External agent took claim tag");
  

} EXPORT_SYMBOL_GPL(coresight_disclaim_device_unlocked); diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h index 38bb4e8b50ef..6e8cf55aee0a 100644 --- a/drivers/hwtracing/coresight/coresight-priv.h +++ b/drivers/hwtracing/coresight/coresight-priv.h @@ -36,7 +36,10 @@ extern const struct device_type coresight_dev_type[];

• See PSCI - ARM DEN 0022D, Section: 6.8.1 Debug and Trace save and restore.

*/ #define CORESIGHT_CLAIM_MASK GENMASK(1, 0) -#define CORESIGHT_CLAIM_SELF_HOSTED BIT(1) +#define CORESIGHT_CLAIM_FREE 0 +#define CORESIGHT_CLAIM_EXTERNAL 1 +#define CORESIGHT_CLAIM_SELF_HOSTED 2 +#define CORESIGHT_CLAIM_INVALID 3 #define TIMEOUT_US 100 #define BMVAL(val, lsb, msb) ((val & GENMASK(msb, lsb)) >> lsb)

-- 2.34.1