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/*
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2019 Western Digital Corporation or its affiliates.
*
* Authors:
* Anup Patel <anup.patel@wdc.com>
*/
#include <sbi/riscv_io.h>
#include <sbi/sbi_console.h>
#include <sbi_utils/serial/sifive-uart.h>
/* clang-format off */
#define UART_REG_TXFIFO 0
#define UART_REG_RXFIFO 1
#define UART_REG_TXCTRL 2
#define UART_REG_RXCTRL 3
#define UART_REG_IE 4
#define UART_REG_IP 5
#define UART_REG_DIV 6
#define UART_TXFIFO_FULL 0x80000000
#define UART_RXFIFO_EMPTY 0x80000000
#define UART_RXFIFO_DATA 0x000000ff
#define UART_TXCTRL_TXEN 0x1
#define UART_RXCTRL_RXEN 0x1
/* clang-format on */
static volatile void *uart_base;
static u32 uart_in_freq;
static u32 uart_baudrate;
/**
* Find minimum divisor divides in_freq to max_target_hz;
* Based on uart driver n SiFive FSBL.
*
* f_baud = f_in / (div + 1) => div = (f_in / f_baud) - 1
* The nearest integer solution requires rounding up as to not exceed max_target_hz.
* div = ceil(f_in / f_baud) - 1
* = floor((f_in - 1 + f_baud) / f_baud) - 1
* This should not overflow as long as (f_in - 1 + f_baud) does not exceed
* 2^32 - 1, which is unlikely since we represent frequencies in kHz.
*/
static inline unsigned int uart_min_clk_divisor(uint64_t in_freq,
uint64_t max_target_hz)
{
uint64_t quotient = (in_freq + max_target_hz - 1) / (max_target_hz);
/* Avoid underflow */
if (quotient == 0) {
return 0;
} else {
return quotient - 1;
}
}
static u32 get_reg(u32 num)
{
return readl(uart_base + (num * 0x4));
}
static void set_reg(u32 num, u32 val)
{
writel(val, uart_base + (num * 0x4));
}
static void sifive_uart_putc(char ch)
{
while (get_reg(UART_REG_TXFIFO) & UART_TXFIFO_FULL)
;
set_reg(UART_REG_TXFIFO, ch);
}
static int sifive_uart_getc(void)
{
u32 ret = get_reg(UART_REG_RXFIFO);
if (!(ret & UART_RXFIFO_EMPTY))
return ret & UART_RXFIFO_DATA;
return -1;
}
static struct sbi_console_device sifive_console = {
.name = "sifive_uart",
.console_putc = sifive_uart_putc,
.console_getc = sifive_uart_getc
};
int sifive_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
{
uart_base = (volatile void *)base;
uart_in_freq = in_freq;
uart_baudrate = baudrate;
/* Configure baudrate */
if (in_freq)
set_reg(UART_REG_DIV, uart_min_clk_divisor(in_freq, baudrate));
/* Disable interrupts */
set_reg(UART_REG_IE, 0);
/* Enable TX */
set_reg(UART_REG_TXCTRL, UART_TXCTRL_TXEN);
/* Enable Rx */
set_reg(UART_REG_RXCTRL, UART_RXCTRL_RXEN);
sbi_console_set_device(&sifive_console);
return 0;
}
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