feat(cpufeat): add AArch32 PAN detection support

FEAT_PAN is implemented in AArch32 as well, provide the helper functions
to query the feature availability at runtime.

Change-Id: I375e3eb7b05955ea28a092ba99bb93302af48a0e
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

include/arch/aarch32/arch.h

@@ -119,6 +119,10 @@
 #define ID_DFR1_MTPMU_MASK	U(0xf)
 #define ID_DFR1_MTPMU_SUPPORTED	U(1)
 
+/* ID_MMFR3 definitions */
+#define ID_MMFR3_PAN_SHIFT	U(16)
+#define ID_MMFR3_PAN_MASK	U(0xf)
+
 /* ID_MMFR4 definitions */
 #define ID_MMFR4_CNP_SHIFT	U(12)
 #define ID_MMFR4_CNP_LENGTH	U(4)
@@ -533,6 +537,7 @@
 #define DCISW		p15, 0, c7, c6, 2
 #define CTR		p15, 0, c0, c0, 1
 #define CNTFRQ		p15, 0, c14, c0, 0
+#define ID_MMFR3	p15, 0, c0, c1, 7
 #define ID_MMFR4	p15, 0, c0, c2, 6
 #define ID_DFR0		p15, 0, c0, c1, 2
 #define ID_DFR1		p15, 0, c0, c3, 5

include/arch/aarch32/arch_features.h

@@ -116,4 +116,22 @@ static inline bool is_feat_spe_supported(void)
 	return false;
 }
 
+static inline unsigned int read_feat_pan_id_field(void)
+{
+	return ISOLATE_FIELD(read_id_mmfr3(), ID_MMFR3_PAN);
+}
+
+static inline bool is_feat_pan_supported(void)
+{
+	if (ENABLE_FEAT_PAN == FEAT_STATE_DISABLED) {
+		return false;
+	}
+
+	if (ENABLE_FEAT_PAN == FEAT_STATE_ALWAYS) {
+		return true;
+	}
+
+	return read_feat_pan_id_field() != 0U;
+}
+
 #endif /* ARCH_FEATURES_H */

include/arch/aarch32/arch_helpers.h

@@ -217,6 +217,7 @@ DEFINE_SYSREG_RW_FUNCS(cpsr)
  ******************************************************************************/
 DEFINE_COPROCR_READ_FUNC(mpidr, MPIDR)
 DEFINE_COPROCR_READ_FUNC(midr, MIDR)
+DEFINE_COPROCR_READ_FUNC(id_mmfr3, ID_MMFR3)
 DEFINE_COPROCR_READ_FUNC(id_mmfr4, ID_MMFR4)
 DEFINE_COPROCR_READ_FUNC(id_dfr0, ID_DFR0)
 DEFINE_COPROCR_READ_FUNC(id_pfr0, ID_PFR0)