coresight: etm4x: Expose trcdevarch via sysfs

Expose the TRCDEVARCH register via the sysfs for component
detection. Given that the TRCIDR1 may not completely identify
the ETM component and instead need to use TRCDEVARCH, expose
this via sysfs for tools to use it for identification.

Link: https://lore.kernel.org/r/20210110224850.1880240-21-suzuki.poulose@arm.com
Cc: Mike Leach <mike.leach@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/20210201181351.1475223-23-mathieu.poirier@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x

@@ -371,6 +371,14 @@ Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
 Description:	(Read) Print the content of the Device ID Register
 		(0xFC8).  The value is taken directly from the HW.
 
+What:		/sys/bus/coresight/devices/etm<N>/mgmt/trcdevarch
+Date:		January 2021
+KernelVersion:	5.12
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(Read) Print the content of the Device Architecture Register
+		(offset 0xFBC).  The value is taken directly read
+		from the HW.
+
 What:		/sys/bus/coresight/devices/etm<N>/mgmt/trcdevtype
 Date:		April 2015
 KernelVersion:	4.01

drivers/hwtracing/coresight/coresight-etm4x-sysfs.c

@@ -2442,6 +2442,7 @@ static struct attribute *coresight_etmv4_mgmt_attrs[] = {
 	coresight_etm4x_reg(trcoslsr, TRCOSLSR),
 	coresight_etm4x_reg(trcconfig, TRCCONFIGR),
 	coresight_etm4x_reg(trctraceid, TRCTRACEIDR),
+	coresight_etm4x_reg(trcdevarch, TRCDEVARCH),
 	NULL,
 };