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path: root/lib/sbi/sbi_ecall_dbcn.c
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/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Ventana Micro Systems Inc.
 *
 * Authors:
 *   Anup Patel <apatel@ventanamicro.com>
 */

#include <sbi/sbi_console.h>
#include <sbi/sbi_domain.h>
#include <sbi/sbi_error.h>
#include <sbi/sbi_ecall.h>
#include <sbi/sbi_ecall_interface.h>
#include <sbi/sbi_trap.h>
#include <sbi/riscv_asm.h>

static int sbi_ecall_dbcn_handler(unsigned long extid, unsigned long funcid,
				  const struct sbi_trap_regs *regs,
				  unsigned long *out_val,
				  struct sbi_trap_info *out_trap)
{
	ulong smode = (csr_read(CSR_MSTATUS) & MSTATUS_MPP) >>
			MSTATUS_MPP_SHIFT;

	switch (funcid) {
	case SBI_EXT_DBCN_CONSOLE_WRITE:
	case SBI_EXT_DBCN_CONSOLE_READ:
		/*
		 * On RV32, the M-mode can only access the first 4GB of
		 * the physical address space because M-mode does not have
		 * MMU to access full 34-bit physical address space.
		 *
		 * Based on above, we simply fail if the upper 32bits of
		 * the physical address (i.e. a2 register) is non-zero on
		 * RV32.
		 */
#if __riscv_xlen == 32
		if (regs->a2)
			return SBI_ERR_FAILED;
#endif
		if (!sbi_domain_check_addr_range(sbi_domain_thishart_ptr(),
					regs->a1, regs->a0, smode,
					SBI_DOMAIN_READ|SBI_DOMAIN_WRITE))
			return SBI_ERR_INVALID_PARAM;
		if (funcid == SBI_EXT_DBCN_CONSOLE_WRITE)
			*out_val = sbi_nputs((const char *)regs->a1, regs->a0);
		else
			*out_val = sbi_ngets((char *)regs->a1, regs->a0);
		return 0;
	case SBI_EXT_DBCN_CONSOLE_WRITE_BYTE:
		sbi_putc(regs->a0);
		return 0;
	default:
		break;
	}

	return SBI_ENOTSUPP;
}

static int sbi_ecall_dbcn_probe(unsigned long extid, unsigned long *out_val)
{
	*out_val = sbi_console_get_device() ? 1 : 0;
	return 0;
}

struct sbi_ecall_extension ecall_dbcn = {
	.extid_start = SBI_EXT_DBCN,
	.extid_end = SBI_EXT_DBCN,
	.handle = sbi_ecall_dbcn_handler,
	.probe = sbi_ecall_dbcn_probe,
};