coresight: tmc-etr: Check if non-secure access is enabled

CoreSight TMC-ETR must have the non-secure invasive debug access
enabled for use by self-hosted tracing. Without it, there is no
point in enabling the ETR. So, let us check it in the TMC_AUTHSTATUS
register and fail the probe if it is disabled.

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>
Link: https://lore.kernel.org/r/20190829202842.580-7-mathieu.poirier@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-tmc.c

@@ -236,6 +236,7 @@ coresight_tmc_reg(ffcr, TMC_FFCR);
 coresight_tmc_reg(mode, TMC_MODE);
 coresight_tmc_reg(pscr, TMC_PSCR);
 coresight_tmc_reg(axictl, TMC_AXICTL);
+coresight_tmc_reg(authstatus, TMC_AUTHSTATUS);
 coresight_tmc_reg(devid, CORESIGHT_DEVID);
 coresight_tmc_reg64(rrp, TMC_RRP, TMC_RRPHI);
 coresight_tmc_reg64(rwp, TMC_RWP, TMC_RWPHI);
@@ -255,6 +256,7 @@ static struct attribute *coresight_tmc_mgmt_attrs[] = {
 	&dev_attr_devid.attr,
 	&dev_attr_dba.attr,
 	&dev_attr_axictl.attr,
+	&dev_attr_authstatus.attr,
 	NULL,
 };
 
@@ -342,6 +344,13 @@ static inline bool tmc_etr_can_use_sg(struct device *dev)
 	return fwnode_property_present(dev->fwnode, "arm,scatter-gather");
 }
 
+static inline bool tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)
+{
+	u32 auth = readl_relaxed(drvdata->base + TMC_AUTHSTATUS);
+
+	return (auth & TMC_AUTH_NSID_MASK) == 0x3;
+}
+
 /* Detect and initialise the capabilities of a TMC ETR */
 static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps)
 {
@@ -349,6 +358,9 @@ static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps)
 	u32 dma_mask = 0;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(parent);
 
+	if (!tmc_etr_has_non_secure_access(drvdata))
+		return -EACCES;
+
 	/* Set the unadvertised capabilities */
 	tmc_etr_init_caps(drvdata, (u32)(unsigned long)dev_caps);
 

drivers/hwtracing/coresight/coresight-tmc.h

@@ -39,6 +39,7 @@
 #define TMC_ITATBCTR2		0xef0
 #define TMC_ITATBCTR1		0xef4
 #define TMC_ITATBCTR0		0xef8
+#define TMC_AUTHSTATUS		0xfb8
 
 /* register description */
 /* TMC_CTL - 0x020 */
@@ -90,6 +91,8 @@
 #define TMC_DEVID_AXIAW_SHIFT	17
 #define TMC_DEVID_AXIAW_MASK	0x7f
 
+#define TMC_AUTH_NSID_MASK	GENMASK(1, 0)
+
 enum tmc_config_type {
 	TMC_CONFIG_TYPE_ETB,
 	TMC_CONFIG_TYPE_ETR,