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lib: utils: Add LiteX UART support

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Add support for the UART provided by the LiteX SoC
framework (https://github.com/enjoy-digital/litex),
based on its FDT info (described in the Linux tree at
Documentation/devicetree/bindings/serial/litex,liteuart.yaml).

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
This commit is contained in:
Gabriel Somlo
2021-11-16 14:17:04 -05:00
committed by Anup Patel
parent d335a178d8
commit 52af6e4b52
5 changed files with 123 additions and 0 deletions
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63
lib/utils/serial/litex-uart.c Normal file
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/*
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2021 Gabriel Somlo
*
* Authors:
* Gabriel Somlo <gsomlo@gmail.com>
*/
#include <sbi/riscv_io.h>
#include <sbi/sbi_console.h>
#include <sbi_utils/serial/litex-uart.h>
/* clang-format off */
#define UART_REG_RXTX 0
#define UART_REG_TXFULL 1
#define UART_REG_RXEMPTY 2
#define UART_REG_EV_STATUS 3
#define UART_REG_EV_PENDING 4
#define UART_REG_EV_ENABLE 5
/* clang-format on */
static volatile u32 *uart_base;
static u8 get_reg(u8 reg)
{
return readb(uart_base + reg);
}
static void set_reg(u8 reg, u8 val)
{
writeb(val, uart_base + reg);
}
static void litex_uart_putc(char ch)
{
while (get_reg(UART_REG_TXFULL));
set_reg(UART_REG_RXTX, ch);
}
static int litex_uart_getc(void)
{
if (get_reg(UART_REG_RXEMPTY))
return -1;
else
return get_reg(UART_REG_RXTX);
}
static struct sbi_console_device litex_console = {
.name = "litex_uart",
.console_putc = litex_uart_putc,
.console_getc = litex_uart_getc
};
int litex_uart_init(unsigned long base)
{
uart_base = (volatile u32 *)base;
set_reg(UART_REG_EV_ENABLE, 0); /* UART in polling mode: disable IRQ */
sbi_console_set_device(&litex_console);
return 0;
}