xref: /kvm-unit-tests/lib/riscv/io.c (revision fbeeb84737e393649bb27b68142e2783c3f1b523)

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Each architecture must implement puts() and exit() with the I/O
 * devices exposed from QEMU, e.g. ns16550a.
 *
 * Copyright (C) 2023, Ventana Micro Systems Inc., Andrew Jones <ajones@ventanamicro.com>
 */
#include <libcflat.h>
#include <config.h>
#include <devicetree.h>
#include <asm/io.h>
#include <asm/sbi.h>
#include <asm/setup.h>
#include <asm/spinlock.h>

#define UART_LSR_OFFSET		5
#define UART_LSR_THRE		0x20

/*
 * Use this guess for the uart base in order to make an attempt at
 * having earlier printf support. We'll overwrite it with the real
 * base address that we read from the device tree later. This is
 * the address we expect the virtual machine manager to put in
 * its generated device tree.
 */
#define UART_EARLY_BASE ((u8 *)(unsigned long)CONFIG_UART_EARLY_BASE)
static volatile u8 *uart0_base = UART_EARLY_BASE;
static u32 uart0_reg_width = 1;
static u32 uart0_reg_shift;
static struct spinlock uart_lock;

static u32 uart0_read(u32 num)
{
	u32 offset = num << uart0_reg_shift;

	if (uart0_reg_width == 1)
		return readb(uart0_base + offset);
	else if (uart0_reg_width == 2)
		return readw(uart0_base + offset);
	else
		return readl(uart0_base + offset);
}

static void uart0_write(u32 num, u32 val)
{
	u32 offset = num << uart0_reg_shift;

	if (uart0_reg_width == 1)
		writeb(val, uart0_base + offset);
	else if (uart0_reg_width == 2)
		writew(val, uart0_base + offset);
	else
		writel(val, uart0_base + offset);
}

static void uart0_init_fdt(void)
{
	const char *compatible[] = {"ns16550a"};
	struct dt_pbus_reg base;
	int i, ret;

	ret = dt_get_default_console_node();
	assert(ret >= 0 || ret == -FDT_ERR_NOTFOUND);

	if (ret == -FDT_ERR_NOTFOUND) {
		for (i = 0; i < ARRAY_SIZE(compatible); i++) {
			ret = dt_pbus_get_base_compatible(compatible[i], &base);
			assert(ret == 0 || ret == -FDT_ERR_NOTFOUND);
			if (ret == 0)
				break;
		}

		if (ret) {
			printf("%s: Compatible uart not found in the device tree, aborting...\n",
			       __func__);
			abort();
		}
	} else {
		const fdt32_t *val;
		int len;

		val = fdt_getprop(dt_fdt(), ret, "reg-shift", &len);
		if (len == sizeof(*val))
			uart0_reg_shift = fdt32_to_cpu(*val);

		val = fdt_getprop(dt_fdt(), ret, "reg-io-width", &len);
		if (len == sizeof(*val))
			uart0_reg_width = fdt32_to_cpu(*val);

		ret = dt_pbus_translate_node(ret, 0, &base);
		assert(ret == 0);
	}

	uart0_base = ioremap(base.addr, base.size);
}

static void uart0_init_acpi(void)
{
	assert_msg(false, "ACPI not available");
}

void io_init(void)
{
	if (dt_available())
		uart0_init_fdt();
	else
		uart0_init_acpi();

	if (uart0_base != UART_EARLY_BASE) {
		printf("WARNING: early print support may not work. "
		       "Found uart at %p, but early base is %p.\n",
		       uart0_base, UART_EARLY_BASE);
	}
}

void puts(const char *s)
{
	spin_lock(&uart_lock);
	while (*s) {
		while (!(uart0_read(UART_LSR_OFFSET) & UART_LSR_THRE))
			;
		uart0_write(0, *s++);
	}
	spin_unlock(&uart_lock);
}

/*
 * Defining halt to take 'code' as an argument guarantees that it will
 * be in a0 when we halt. That gives us a final chance to see the exit
 * status while inspecting the halted unit test state.
 */
void halt(int code);

void exit(int code)
{
	printf("\nEXIT: STATUS=%d\n", ((code) << 1) | 1);
	sbi_shutdown();
	halt(code);
	__builtin_unreachable();
}