feat(trbe): add trbe under feature detection mechanism

This change adds "FEAT_TRBE" to be part of feature detection mechanism.

Previously feature enablement flags were of boolean type, containing
either 0 or 1. With the introduction of feature detection procedure
we now support three states for feature enablement build flags(0 to 2).

Accordingly, "ENABLE_TRBE_FOR_NS" flag is now modified from boolean
to numeric type to align with the feature detection.

Change-Id: I53d3bc8dc2f6eac63feef22dfd627f3a48480afc
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>

Makefile

@@ -1045,7 +1045,6 @@ $(eval $(call assert_booleans,\
         COT_DESC_IN_DTB \
         USE_SP804_TIMER \
         PSA_FWU_SUPPORT \
-        ENABLE_TRBE_FOR_NS \
         ENABLE_SYS_REG_TRACE_FOR_NS \
         ENABLE_MPMM \
         ENABLE_MPMM_FCONF \
@@ -1062,6 +1061,7 @@ $(eval $(call assert_numerics,\
         CTX_INCLUDE_MTE_REGS \
         CTX_INCLUDE_NEVE_REGS \
         ENABLE_BRBE_FOR_NS \
+        ENABLE_TRBE_FOR_NS \
         ENABLE_BTI \
         ENABLE_PAUTH \
         ENABLE_FEAT_AMUv1 \

common/feat_detect.c

@@ -244,6 +244,16 @@ static void read_feat_brbe(void)
 #endif
 }
 
+/******************************************************
+ * Feature : FEAT_TRBE (Trace Buffer Extension)
+ *****************************************************/
+static void read_feat_trbe(void)
+{
+#if (ENABLE_TRBE_FOR_NS == FEAT_STATE_1)
+	feat_detect_panic(is_feat_trbe_present(), "TRBE");
+#endif
+}
+
 /***********************************************************************************
  * TF-A supports many Arm architectural features starting from arch version
  * (8.0 till 8.7+). These features are mostly enabled through build flags. This
@@ -306,6 +316,7 @@ void detect_arch_features(void)
 
 	/* v9.0 features */
 	read_feat_brbe();
+	read_feat_trbe();
 
 	/* v9.2 features */
 	read_feat_rme();

docs/getting_started/build-options.rst

@@ -988,11 +988,12 @@ Common build options
   0 to 2, to align with the ``FEATURE_DETECTION`` mechanism. The default is 0
   and it is automatically disabled when the target architecture is AArch32.
 
-- ``ENABLE_TRBE_FOR_NS``: This flag is used to enable access of trace buffer
+- ``ENABLE_TRBE_FOR_NS``: Numeric value to enable access of trace buffer
   control registers from NS ELs, NS-EL2 or NS-EL1(when NS-EL2 is implemented
   but unused) when FEAT_TRBE is implemented. TRBE is an optional architectural
-  feature for AArch64. The default is 0 and it is automatically disabled when
+  feature for AArch64. This flag can take the values  0 to 2, to align with the
-  the target architecture is AArch32.
+  ``FEATURE_DETECTION`` mechanism. The default is 0 and it is automatically
+  disabled when the target architecture is AArch32.
 
 - ``ENABLE_SYS_REG_TRACE_FOR_NS``: Boolean option to enable trace system
   registers access from NS ELs, NS-EL2 or NS-EL1 (when NS-EL2 is implemented

include/arch/aarch64/arch_features.h

@@ -234,5 +234,13 @@ static inline bool is_feat_brbe_present(void)
 		ID_AA64DFR0_BRBE_MASK) == ID_AA64DFR0_BRBE_SUPPORTED);
 }
 
+/*******************************************************************************
+ * Function to identify the presence of FEAT_TRBE (Trace Buffer Extension)
+ ******************************************************************************/
+static inline bool is_feat_trbe_present(void)
+{
+	return (((read_id_aa64dfr0_el1() >> ID_AA64DFR0_TRACEBUFFER_SHIFT) &
+		ID_AA64DFR0_TRACEBUFFER_MASK) == ID_AA64DFR0_TRACEBUFFER_SUPPORTED);
+}
 
 #endif /* ARCH_FEATURES_H */

lib/extensions/trbe/trbe.c

@@ -1,10 +1,11 @@
 /*
- * Copyright (c) 2021, Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2022, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <arch.h>
+#include <arch_features.h>
 #include <arch_helpers.h>
 #include <lib/el3_runtime/pubsub.h>
 #include <lib/extensions/trbe.h>
@@ -18,20 +19,11 @@ static void tsb_csync(void)
 	__asm__ volatile("hint #18");
 }
 
-static bool trbe_supported(void)
-{
-	uint64_t features;
-
-	features = read_id_aa64dfr0_el1() >> ID_AA64DFR0_TRACEBUFFER_SHIFT;
-	return ((features & ID_AA64DFR0_TRACEBUFFER_MASK) ==
-		ID_AA64DFR0_TRACEBUFFER_SUPPORTED);
-}
-
 void trbe_enable(void)
 {
 	uint64_t val;
 
-	if (trbe_supported()) {
+	if (is_feat_trbe_present()) {
 		/*
 		 * MDCR_EL3.NSTB = 0b11
 		 * Allow access of trace buffer control registers from NS-EL1
@@ -46,7 +38,7 @@ void trbe_enable(void)
 
 static void *trbe_drain_trace_buffers_hook(const void *arg __unused)
 {
-	if (trbe_supported()) {
+	if (is_feat_trbe_present()) {
 		/*
 		 * Before switching from normal world to secure world
 		 * the trace buffers need to be drained out to memory. This is