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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 char *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 char *)base;
- uart_in_freq = in_freq;
- uart_baudrate = baudrate;
- /* Configure baudrate */
- if (in_freq && baudrate)
- 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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