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Message-Id: <20251027223545.2801-2-mike.leach@linaro.org>
Date: Mon, 27 Oct 2025 22:35:45 +0000
From: Mike Leach <mike.leach@...aro.org>
To: coresight@...ts.linaro.org,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Cc: suzuki.poulose@....com,
leo.yan@....com,
james.clark@...aro.org,
Mike Leach <mike.leach@...aro.org>
Subject: [PATCH v2 1/1] coresight: fix issue where coresight component has no claimtags
Coresight components have 0 to 8 claim tag bits. ARM recommends 4 and
the implemented claim tag protocol uses two of these.
If a component has insufficient claim tags then the protocol incorrectly
returns an error when attempting to claim a component.
Fix by reading CLAIMSET to establish then actual number of claim tags
and return success when attempting to claim a component were there are
insufficient tags to implement the protocol.
Signed-off-by: Mike Leach <mike.leach@...aro.org>
---
drivers/hwtracing/coresight/coresight-core.c | 46 ++++++++++++++++++--
drivers/hwtracing/coresight/coresight-priv.h | 10 +++++
include/linux/coresight.h | 15 +++++++
3 files changed, 68 insertions(+), 3 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 3267192f0c1c..61b4902b0ead 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -131,6 +131,39 @@ coresight_find_out_connection(struct coresight_device *csdev,
return ERR_PTR(-ENODEV);
}
+/*
+ * Reading CLAiMSET returns a bitfield representing the number of claim tags
+ * implemented from bit 0 to bit nTag-1, valid bits set to 1.
+ *
+ * Claim protocol requires 2 bits so test for MS bit required,
+ * bit 1 - CORESIGHT_CLAIM_BIT_PROTOCOL_HI
+ *
+ * return true if sufficient claim tags implemented for protocol
+ */
+static bool coresight_claim_tags_implemented_unlocked(struct csdev_access *csa)
+{
+ u32 claim_bits_impl = FIELD_GET(CORESIGHT_CLAIM_BITS_MAX_MASK,
+ csdev_access_relaxed_read32(csa, CORESIGHT_CLAIMSET));
+ return ((claim_bits_impl & CORESIGHT_CLAIM_BIT_PROTOCOL_HI) != 0);
+}
+
+/*
+ * check if we can use the claim tag protocol.
+ *
+ * If currently unknown - read register to determine if sufficient tags and
+ * save value, otherwise return current value.
+ */
+static bool coresight_check_use_claim_tag_unlocked(struct coresight_device *csdev)
+{
+ if (csdev->claim_tag_info == CS_CLAIM_TAG_UNKNOWN) {
+ if (coresight_claim_tags_implemented_unlocked(&csdev->access))
+ csdev->claim_tag_info = CS_CLAIM_TAG_STD_PROTOCOL;
+ else
+ csdev->claim_tag_info = CS_CLAIM_TAG_NOT_IMPL;
+ }
+ return (csdev->claim_tag_info == CS_CLAIM_TAG_STD_PROTOCOL);
+}
+
static u32 coresight_read_claim_tags_unlocked(struct coresight_device *csdev)
{
return FIELD_GET(CORESIGHT_CLAIM_MASK,
@@ -156,6 +189,9 @@ EXPORT_SYMBOL_GPL(coresight_clear_self_claim_tag);
void coresight_clear_self_claim_tag_unlocked(struct csdev_access *csa)
{
+ if (!coresight_claim_tags_implemented_unlocked(csa))
+ return;
+
csdev_access_relaxed_write32(csa, CORESIGHT_CLAIM_SELF_HOSTED,
CORESIGHT_CLAIMCLR);
isb();
@@ -175,12 +211,13 @@ 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;
- csa = &csdev->access;
+ if (!coresight_check_use_claim_tag_unlocked(csdev))
+ return 0;
+
tag = coresight_read_claim_tags_unlocked(csdev);
switch (tag) {
@@ -190,7 +227,7 @@ int coresight_claim_device_unlocked(struct coresight_device *csdev)
return 0;
/* There was a race setting the tag, clean up and fail */
- coresight_clear_self_claim_tag_unlocked(csa);
+ coresight_clear_self_claim_tag_unlocked(&csdev->access);
dev_dbg(&csdev->dev, "Busy: Couldn't set self claim tag");
return -EBUSY;
@@ -237,6 +274,9 @@ void coresight_disclaim_device_unlocked(struct coresight_device *csdev)
if (WARN_ON(!csdev))
return;
+ if (!coresight_check_use_claim_tag_unlocked(csdev))
+ return;
+
if (coresight_read_claim_tags_unlocked(csdev) == CORESIGHT_CLAIM_SELF_HOSTED)
coresight_clear_self_claim_tag_unlocked(&csdev->access);
else
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 33e22b1ba043..270f179c8535 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -41,6 +41,16 @@ extern const struct device_type coresight_dev_type[];
#define CORESIGHT_CLAIM_SELF_HOSTED 2
#define CORESIGHT_CLAIM_INVALID 3
+/*
+ * Coresight specification defines a maximum of 8 claim tag bits.
+ * The precise number is implementation defined, and may be obtained by
+ * reading the CLAIMSET register.
+ */
+#define CORESIGHT_CLAIM_BITS_MAX_MASK GENMASK(7, 0)
+
+/* MS Bit required by the protocol */
+#define CORESIGHT_CLAIM_BIT_PROTOCOL_HI BIT(1)
+
#define TIMEOUT_US 100
#define BMVAL(val, lsb, msb) ((val & GENMASK(msb, lsb)) >> lsb)
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 6de59ce8ef8c..fefe4317a793 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -242,6 +242,19 @@ struct coresight_trace_id_map {
raw_spinlock_t lock;
};
+/*
+ * Coresight claim tag info:
+ * CS_CLAIM_TAG_UNKNOWN - not yet checked.
+ * CS_CLAIM_TAG_STD_PROTOCOL - using standard claim/release protocol.
+ * CS_CLAIM_TAG_NOT_IMPL - no claim tags available.
+ */
+enum coresight_claim_tag_info {
+ CS_CLAIM_TAG_UNKNOWN,
+ CS_CLAIM_TAG_STD_PROTOCOL,
+ CS_CLAIM_TAG_NOT_IMPL,
+};
+
+
/**
* struct coresight_device - representation of a device as used by the framework
* @pdata: Platform data with device connections associated to this device.
@@ -265,6 +278,7 @@ struct coresight_trace_id_map {
* CS_MODE_SYSFS. Otherwise it must be accessed from inside the
* spinlock.
* @orphan: true if the component has connections that haven't been linked.
+ * @claim_tag_info: how the device is using claim tags.
* @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs
* by writing a 1 to the 'enable_sink' file. A sink can be
* activated but not yet enabled. Enabling for a _sink_ happens
@@ -291,6 +305,7 @@ struct coresight_device {
local_t mode;
int refcnt;
bool orphan;
+ enum coresight_claim_tag_info claim_tag_info;
/* sink specific fields */
bool sysfs_sink_activated;
struct dev_ext_attribute *ea;
--
2.32.0
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