1 /*
2  * Copyright (c) 2021, Arm Limited. All rights reserved.
3  *
4  * SPDX-License-Identifier: BSD-3-Clause
5  */
6 
7 #include <stdbool.h>
8 
9 #include <arch.h>
10 #include <arch_helpers.h>
11 #include <lib/extensions/sys_reg_trace.h>
12 
sys_reg_trace_supported(void)13 static bool sys_reg_trace_supported(void)
14 {
15 	uint64_t features;
16 
17 	features = read_id_aa64dfr0_el1() >> ID_AA64DFR0_TRACEVER_SHIFT;
18 	return ((features & ID_AA64DFR0_TRACEVER_MASK) ==
19 		ID_AA64DFR0_TRACEVER_SUPPORTED);
20 }
21 
sys_reg_trace_enable(cpu_context_t * ctx)22 void sys_reg_trace_enable(cpu_context_t *ctx)
23 {
24 	uint64_t val;
25 
26 	if (sys_reg_trace_supported()) {
27 		/* Retrieve CPTR_EL3 value from the given context 'ctx',
28 		 * and update CPTR_EL3.TTA bit to 0.
29 		 * This function is called while switching context to NS to
30 		 * allow system trace register access to NS-EL2 and NS-EL1
31 		 * when NS-EL2 is implemented but not used.
32 		 */
33 		val = read_ctx_reg(get_el3state_ctx(ctx), CTX_CPTR_EL3);
34 		val &= ~TTA_BIT;
35 		write_ctx_reg(get_el3state_ctx(ctx), CTX_CPTR_EL3, val);
36 	}
37 }
38