lib/extensions/sys_reg_trace/aarch64/sys_reg_trace.c

/*
 * Copyright (c) 2021-2023, Arm Limited. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdbool.h>

#include <arch.h>
#include <arch_helpers.h>
#include <lib/extensions/sys_reg_trace.h>

void sys_reg_trace_enable(cpu_context_t *ctx)
{
	uint64_t val;

	/* Retrieve CPTR_EL3 value from the given context 'ctx',
	 * and update CPTR_EL3.TTA bit to 0.
	 * This function is called while switching context to NS to
	 * allow system trace register access to NS-EL2 and NS-EL1
	 * when NS-EL2 is implemented but not used.
	 */
	val = read_ctx_reg(get_el3state_ctx(ctx), CTX_CPTR_EL3);
	val &= ~TTA_BIT;
	write_ctx_reg(get_el3state_ctx(ctx), CTX_CPTR_EL3, val);
}

void sys_reg_trace_init_el2_unused(void)
{
	/*
	 * CPTR_EL2.TTA: Set to zero so that Non-secure System register accesses
	 *  to the trace registers from both Execution states do not trap to
	 *  EL2. If PE trace unit System registers are not implemented then this
	 *  bit is reserved, and must be set to zero.
	 */
	write_cptr_el2(read_cptr_el2() & ~CPTR_EL2_TTA_BIT);
}