diff options
author | Ian Moffett <ian@osmora.org> | 2024-07-06 01:11:44 -0400 |
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committer | Ian Moffett <ian@osmora.org> | 2024-07-06 01:12:35 -0400 |
commit | abced67cbb8a19369ae1a5aaafd6318f0b2ee069 (patch) | |
tree | 59ad944fa97a110216d35d535dc98ca3482bd07e /sys/arch/amd64/amd64 | |
parent | bf9e5005b66c3e1219340837d3c29443dd0fb4e1 (diff) |
kernel/amd64: Add 8250 UART driver
Signed-off-by: Ian Moffett <ian@osmora.org>
Diffstat (limited to 'sys/arch/amd64/amd64')
-rw-r--r-- | sys/arch/amd64/amd64/uart.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/sys/arch/amd64/amd64/uart.c b/sys/arch/amd64/amd64/uart.c new file mode 100644 index 0000000..9c78434 --- /dev/null +++ b/sys/arch/amd64/amd64/uart.c @@ -0,0 +1,81 @@ +/* + * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of Hyra nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +#include <sys/param.h> +#include <machine/uart.h> +#include <machine/pio.h> + +#define UART_COM1 0x3F8 +#define UART_REG(OFFSET) (UART_COM1 + OFFSET) + +static inline bool +uart_transmit_empty(void) +{ + return ISSET(UART_REG(5), BIT(5)); +} + +void +uart_write(char byte) +{ + while (!uart_transmit_empty()); + outb(UART_COM1, byte); +} + +int +uart_init(void) +{ + /* Disable interrupts */ + outb(UART_REG(1), 0x00); + + /* Set DLAB to set baud rate */ + outb(UART_REG(3), 0x80); + + /* Set rate to 57600 baud */ + outb(UART_REG(0), 0x02); + outb(UART_REG(1), 0x00); + + /* Set data word length to 8 bits and clear DLAB */ + outb(UART_REG(3), 0x03); + + /* Disable FIFOs for now... (TODO: Use them) */ + outb(UART_REG(2), 0x00); + + /* Test chip with loopback mode */ + outb(UART_REG(4), 0x10); + outb(UART_REG(0), 0xF0); + if (inb(UART_REG(0) != 0xF0)) + return -1; + + /* + * Mark the data terminal ready and clear + * loopback mode. + */ + outb(UART_REG(4), 0x01); + return 0; +} |