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@linaro.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;