forked from Mirrors/opensbi
7830e98785
When used to read characters from the terminal (e.g., when the SBI
console is used via ecall from linux with `console=hvc0`), we must
acknowledge receipt of each character to "pop" it off the LiteUART
hardware queue, and allow the next character to be made available.
Fixes: 52af6e4b ("lib: utils: Add LiteX UART support")
Suggested-by: Dolu1990 <charles.papon.90@gmail.com>
Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
70 lines
1.3 KiB
C
70 lines
1.3 KiB
C
/*
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2021 Gabriel Somlo
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*
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* Authors:
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* Gabriel Somlo <gsomlo@gmail.com>
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*/
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#include <sbi/riscv_io.h>
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#include <sbi/sbi_console.h>
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#include <sbi_utils/serial/litex-uart.h>
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/* clang-format off */
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#define UART_REG_RXTX 0
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#define UART_REG_TXFULL 1
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#define UART_REG_RXEMPTY 2
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#define UART_REG_EV_STATUS 3
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#define UART_REG_EV_PENDING 4
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#define UART_REG_EV_ENABLE 5
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#define UART_EV_RX 0x2
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/* clang-format on */
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static volatile u32 *uart_base;
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static u8 get_reg(u8 reg)
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{
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return readb(uart_base + reg);
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}
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static void set_reg(u8 reg, u8 val)
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{
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writeb(val, uart_base + reg);
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}
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static void litex_uart_putc(char ch)
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{
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while (get_reg(UART_REG_TXFULL));
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set_reg(UART_REG_RXTX, ch);
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}
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static int litex_uart_getc(void)
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{
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int ret;
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if (get_reg(UART_REG_RXEMPTY))
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return -1;
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ret = get_reg(UART_REG_RXTX);
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set_reg(UART_REG_EV_PENDING, UART_EV_RX); /* ack. char read */
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return ret;
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}
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static struct sbi_console_device litex_console = {
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.name = "litex_uart",
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.console_putc = litex_uart_putc,
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.console_getc = litex_uart_getc
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};
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int litex_uart_init(unsigned long base)
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{
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uart_base = (volatile u32 *)base;
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set_reg(UART_REG_EV_ENABLE, 0); /* UART in polling mode: disable IRQ */
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sbi_console_set_device(&litex_console);
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return 0;
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}
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