feat(brbe): add brbe under feature detection mechanism

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

Previously feature enablement flags were of boolean type, possessing
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_BRBE_FOR_NS" flag is now modified from boolean
to numeric type to align with the feature detection.

Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Change-Id: I1eb52863b4afb10b808e2f0b6584a8a210d0f38c

Makefile

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

common/feat_detect.c

@@ -234,6 +234,16 @@ static void read_feat_rme(void)
 #endif
 }
 
+/******************************************************
+ * Feature : FEAT_BRBE (Branch Record Buffer Extension)
+ *****************************************************/
+static void read_feat_brbe(void)
+{
+#if (ENABLE_BRBE_FOR_NS == FEAT_STATE_1)
+	feat_detect_panic(is_feat_brbe_present(), "BRBE");
+#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
@@ -294,6 +304,9 @@ void detect_arch_features(void)
 	/* v8.7 features */
 	read_feat_hcx();
 
+	/* v9.0 features */
+	read_feat_brbe();
+
 	/* v9.2 features */
 	read_feat_rme();
 }

docs/getting_started/build-options.rst

@@ -982,10 +982,11 @@ Common build options
   functions that wait for an arbitrary time length (udelay and mdelay). The
   default value is 0.
 
-- ``ENABLE_BRBE_FOR_NS``: This flag enables access to the branch record buffer
-  registers from NS ELs when FEAT_BRBE is implemented. BRBE is an optional
-  architectural feature for AArch64. The default is 0 and it is automatically
-  disabled when the target architecture is AArch32.
+- ``ENABLE_BRBE_FOR_NS``: Numeric value to enable access to the branch record
+  buffer registers from NS ELs when FEAT_BRBE is implemented. BRBE is an
+  optional architectural feature for AArch64. This flag can take the values
+  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
   control registers from NS ELs, NS-EL2 or NS-EL1(when NS-EL2 is implemented

include/arch/aarch64/arch_features.h

@@ -224,4 +224,15 @@ static inline unsigned int get_armv8_4_feat_nv_support(void)
 		ID_AA64MMFR2_EL1_NV_MASK));
 }
 
+/*******************************************************************************
+ * Function to identify the presence of FEAT_BRBE (Branch Record Buffer
+ * Extension)
+ ******************************************************************************/
+static inline bool is_feat_brbe_present(void)
+{
+	return (((read_id_aa64dfr0_el1() >> ID_AA64DFR0_BRBE_SHIFT) &
+		ID_AA64DFR0_BRBE_MASK) == ID_AA64DFR0_BRBE_SUPPORTED);
+}
+
+
 #endif /* ARCH_FEATURES_H */

lib/extensions/brbe/brbe.c

@@ -5,22 +5,14 @@
  */
 
 #include <arch.h>
+#include <arch_features.h>
 #include <arch_helpers.h>
 
-static bool brbe_supported(void)
-{
-	uint64_t features;
-
-	features = read_id_aa64dfr0_el1() >> ID_AA64DFR0_BRBE_SHIFT;
-	return ((features & ID_AA64DFR0_BRBE_MASK) ==
-		ID_AA64DFR0_BRBE_SUPPORTED);
-}
-
 void brbe_enable(void)
 {
 	uint64_t val;
 
-	if (brbe_supported()) {
+	if (is_feat_brbe_present()) {
 		/*
 		 * MDCR_EL3.SBRBE = 0b01
 		 *