coresight: Add support for CLAIM tag protocol

Coresight architecture defines CLAIM tags for a device to negotiate
control of the components (external agent vs self-hosted). Each device
has a pair of registers (CLAIMSET & CLAIMCLR) for managing the CLAIM
tags. However, the protocol for the CLAIM tags is IMPLEMENTATION DEFINED.
PSCI has recommendations for the use of the CLAIM tags to negotiate
controls for external agent vs self-hosted use. This patch implements
the recommended protocol by PSCI.

The claim/disclaim operations are performed from the device specific
drivers. The disadvantage is that the calls are sprinkled in each driver,
but this makes the operation much simpler.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index c11da5564a675bac6c8299701800df9ddd1f6723..579f34943bf1ab9fea05ff1cd2079460c1cefc39 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -25,6 +25,13 @@
 #define CORESIGHT_DEVID                0xfc8
 #define CORESIGHT_DEVTYPE      0xfcc
 
+
+/*
+ * Coresight device CLAIM protocol.
+ * See PSCI - ARM DEN 0022D, Section: 6.8.1 Debug and Trace save and restore.
+ */
+#define CORESIGHT_CLAIM_SELF_HOSTED    BIT(1)
+
 #define TIMEOUT_US             100
 #define BMVAL(val, lsb, msb)   ((val & GENMASK(msb, lsb)) >> lsb)
 

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index f4f50753cf75f353358d8597a45321fa27d57aac..2b0df1a0a8df4c8c463e8169fa73b5e279330b60 100644 (file)
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -128,6 +128,92 @@ static int coresight_find_link_outport(struct coresight_device *csdev,
        return -ENODEV;
 }
 
+static inline u32 coresight_read_claim_tags(void __iomem *base)
+{
+       return readl_relaxed(base + CORESIGHT_CLAIMCLR);
+}
+
+static inline bool coresight_is_claimed_self_hosted(void __iomem *base)
+{
+       return coresight_read_claim_tags(base) == CORESIGHT_CLAIM_SELF_HOSTED;
+}
+
+static inline bool coresight_is_claimed_any(void __iomem *base)
+{
+       return coresight_read_claim_tags(base) != 0;
+}
+
+static inline void coresight_set_claim_tags(void __iomem *base)
+{
+       writel_relaxed(CORESIGHT_CLAIM_SELF_HOSTED, base + CORESIGHT_CLAIMSET);
+       isb();
+}
+
+static inline void coresight_clear_claim_tags(void __iomem *base)
+{
+       writel_relaxed(CORESIGHT_CLAIM_SELF_HOSTED, base + CORESIGHT_CLAIMCLR);
+       isb();
+}
+
+/*
+ * coresight_claim_device_unlocked : Claim the device for self-hosted usage
+ * to prevent an external tool from touching this device. As per PSCI
+ * standards, section "Preserving the execution context" => "Debug and Trace
+ * save and Restore", DBGCLAIM[1] is reserved for Self-hosted debug/trace and
+ * DBGCLAIM[0] is reserved for external tools.
+ *
+ * Called with CS_UNLOCKed for the component.
+ * Returns : 0 on success
+ */
+int coresight_claim_device_unlocked(void __iomem *base)
+{
+       if (coresight_is_claimed_any(base))
+               return -EBUSY;
+
+       coresight_set_claim_tags(base);
+       if (coresight_is_claimed_self_hosted(base))
+               return 0;
+       /* There was a race setting the tags, clean up and fail */
+       coresight_clear_claim_tags(base);
+       return -EBUSY;
+}
+
+int coresight_claim_device(void __iomem *base)
+{
+       int rc;
+
+       CS_UNLOCK(base);
+       rc = coresight_claim_device_unlocked(base);
+       CS_LOCK(base);
+
+       return rc;
+}
+
+/*
+ * coresight_disclaim_device_unlocked : Clear the claim tags for the device.
+ * Called with CS_UNLOCKed for the component.
+ */
+void coresight_disclaim_device_unlocked(void __iomem *base)
+{
+
+       if (coresight_is_claimed_self_hosted(base))
+               coresight_clear_claim_tags(base);
+       else
+               /*
+                * The external agent may have not honoured our claim
+                * and has manipulated it. Or something else has seriously
+                * gone wrong in our driver.
+                */
+               WARN_ON_ONCE(1);
+}
+
+void coresight_disclaim_device(void __iomem *base)
+{
+       CS_UNLOCK(base);
+       coresight_disclaim_device_unlocked(base);
+       CS_LOCK(base);
+}
+
 static int coresight_enable_sink(struct coresight_device *csdev,
                                 u32 mode, void *data)
 {

diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 53535821dc25c1d992cee62c24f5289dbbaeecfc..46c67a7648778d8e7e1b0793bd8683567d132fce 100644 (file)
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -257,6 +257,13 @@ extern int coresight_enable(struct coresight_device *csdev);
 extern void coresight_disable(struct coresight_device *csdev);
 extern int coresight_timeout(void __iomem *addr, u32 offset,
                             int position, int value);
+
+extern int coresight_claim_device(void __iomem *base);
+extern int coresight_claim_device_unlocked(void __iomem *base);
+
+extern void coresight_disclaim_device(void __iomem *base);
+extern void coresight_disclaim_device_unlocked(void __iomem *base);
+
 #else
 static inline struct coresight_device *
 coresight_register(struct coresight_desc *desc) { return NULL; }
@@ -266,6 +273,19 @@ coresight_enable(struct coresight_device *csdev) { return -ENOSYS; }
 static inline void coresight_disable(struct coresight_device *csdev) {}
 static inline int coresight_timeout(void __iomem *addr, u32 offset,
                                     int position, int value) { return 1; }
+static inline int coresight_claim_device_unlocked(void __iomem *base)
+{
+       return -EINVAL;
+}
+
+static inline int coresight_claim_device(void __iomem *base)
+{
+       return -EINVAL;
+}
+
+static inline void coresight_disclaim_device(void __iomem *base) {}
+static inline void coresight_disclaim_device_unlocked(void __iomem *base) {}
+
 #endif
 
 #ifdef CONFIG_OF