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https://github.com/riscv-software-src/opensbi.git
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f27203525a
RISC-V doesn't generate exceptions on divide-by-zero, but the result, all bits set, is not likely what people expect either. In all cases where we divide by baudrate there's a chance it's zero (when the DT it came from is "bad"). To avoid difficult to debug situations, leave baudrate dependent registers alone when baudrate is zero, as, also in all cases, it appears we can skip initialization of those registers and still [hopefully] have a functioning UART. Signed-off-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Anup Patel <anup@brainfault.org>
61 lines
1.2 KiB
C
61 lines
1.2 KiB
C
/*
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2020 Vijai Kumar K <vijai@behindbytes.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/shakti-uart.h>
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#define REG_BAUD 0x00
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#define REG_TX 0x04
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#define REG_RX 0x08
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#define REG_STATUS 0x0C
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#define REG_DELAY 0x10
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#define REG_CONTROL 0x14
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#define REG_INT_EN 0x18
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#define REG_IQ_CYCLES 0x1C
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#define REG_RX_THRES 0x20
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#define UART_TX_FULL 0x2
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#define UART_RX_NOT_EMPTY 0x4
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#define UART_RX_FULL 0x8
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static volatile char *uart_base;
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static void shakti_uart_putc(char ch)
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{
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while ((readb(uart_base + REG_STATUS) & UART_TX_FULL))
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;
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writeb(ch, uart_base + REG_TX);
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}
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static int shakti_uart_getc(void)
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{
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if (readb(uart_base + REG_STATUS) & UART_RX_NOT_EMPTY)
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return readb(uart_base + REG_RX);
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return -1;
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}
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static struct sbi_console_device shakti_console = {
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.name = "shakti_uart",
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.console_putc = shakti_uart_putc,
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.console_getc = shakti_uart_getc
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};
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int shakti_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
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{
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uart_base = (volatile char *)base;
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u16 baud;
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if (baudrate) {
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baud = (u16)(in_freq / (16 * baudrate));
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writew(baud, uart_base + REG_BAUD);
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}
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sbi_console_set_device(&shakti_console);
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return 0;
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}
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