x86/uart: new module

1 files changed, 216 insertions, 0 deletions

diff --git a/arch/x86/machine/uart.c b/arch/x86/machine/uart.c
new file mode 100644
index 00000000..6277ae14
--- /dev/null
+++ b/arch/x86/machine/uart.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * TODO Make serial line parameters configurable.
+ * TODO 16550A support.
+ * TODO Interrupt probing and handling.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+
+#include <kern/assert.h>
+#include <kern/console.h>
+#include <kern/init.h>
+#include <kern/macros.h>
+#include <machine/biosmem.h>
+#include <machine/io.h>
+#include <machine/uart.h>
+
+#define UART_BDA_COM1_OFFSET 0
+
+#define UART_REG_THR    0
+#define UART_REG_DLL    0
+#define UART_REG_IER    1
+#define UART_REG_DLH    1
+#define UART_REG_LCR    3
+#define UART_REG_MCR    4
+#define UART_REG_LSR    5
+#define UART_NR_REGS    6
+
+#define UART_THR_EMPTY  0x20
+
+#define UART_LCR_8BITS  0x03
+#define UART_LCR_1S     0x00
+#define UART_LCR_NP     0x00
+#define UART_LCR_BEN    0x40
+#define UART_LCR_DLAB   0x80
+
+#define UART_MCR_DTR    0x01
+#define UART_MCR_RTS    0x02
+#define UART_MCR_AUX2   0x04
+
+#define UART_MAX_DEVS   4
+
+struct uart {
+    struct console console;
+    uint16_t port;
+    uint16_t intr;
+};
+
+static struct uart uart_devs[UART_MAX_DEVS];
+
+static uint16_t uart_intrs[UART_MAX_DEVS] = { 4, 3, 4, 3 };
+
+static uint16_t
+uart_get_addr(const struct uart *uart, uint16_t reg)
+{
+    assert(reg < UART_NR_REGS);
+    return uart->port + reg;
+}
+
+static uint8_t
+uart_read(struct uart *uart, uint16_t reg)
+{
+    return io_read_byte(uart_get_addr(uart, reg));
+}
+
+static void
+uart_write(struct uart *uart, uint16_t reg, uint8_t byte)
+{
+    io_write_byte(uart_get_addr(uart, reg), byte);
+}
+
+static void
+uart_set(struct uart *uart, uint16_t reg, uint8_t mask)
+{
+    uint16_t addr;
+    uint8_t byte;
+
+    addr = uart_get_addr(uart, reg);
+    byte = io_read_byte(addr);
+    byte |= mask;
+    io_write_byte(addr, byte);
+}
+
+static void
+uart_clear(struct uart *uart, uint16_t reg, uint8_t mask)
+{
+    uint16_t addr;
+    uint8_t byte;
+
+    addr = uart_get_addr(uart, reg);
+    byte = io_read_byte(addr);
+    byte &= ~mask;
+    io_write_byte(addr, byte);
+}
+
+static void
+uart_tx_wait(struct uart *uart)
+{
+    uint8_t byte;
+
+    for (;;) {
+        byte = uart_read(uart, UART_REG_LSR);
+
+        if (byte & UART_THR_EMPTY) {
+            break;
+        }
+    }
+}
+
+static struct uart *
+uart_get_dev(size_t i)
+{
+    assert(i < ARRAY_SIZE(uart_devs));
+    return &uart_devs[i];
+}
+
+static struct uart *
+uart_get_from_console(struct console *console)
+{
+    return structof(console, struct uart, console);
+}
+
+static void
+uart_write_char_common(struct uart *uart, char c)
+{
+    uart_tx_wait(uart);
+    uart_write(uart, UART_REG_THR, (uint8_t)c);
+}
+
+static void
+uart_write_char(struct uart *uart, char c)
+{
+    if (c == '\n') {
+        uart_write_char_common(uart, '\r');
+    }
+
+    uart_write_char_common(uart, c);
+}
+
+static void
+uart_console_putc(struct console *console, char c)
+{
+    uart_write_char(uart_get_from_console(console), c);
+}
+
+static void __init
+uart_init(struct uart *uart, uint16_t port, uint16_t intr)
+{
+    uint8_t byte;
+
+    uart->port = port;
+    uart->intr = intr;
+
+    uart_write(uart, UART_REG_IER, 0);
+    uart_write(uart, UART_REG_MCR, UART_MCR_AUX2 | UART_MCR_RTS | UART_MCR_DTR);
+
+    uart_set(uart, UART_REG_LCR, UART_LCR_DLAB);
+    uart_write(uart, UART_REG_DLH, 0);
+    uart_write(uart, UART_REG_DLL, 1);
+    uart_clear(uart, UART_REG_LCR, UART_LCR_DLAB);
+
+    byte = UART_LCR_8BITS | UART_LCR_NP | UART_LCR_1S | UART_LCR_BEN;
+    uart_write(uart, UART_REG_LCR, byte);
+
+    console_init(&uart->console, uart_console_putc);
+    console_register(&uart->console);
+}
+
+void __init
+uart_setup(void)
+{
+    const uint16_t *ptr;
+    size_t i;
+
+    ptr = biosmem_get_bda() + UART_BDA_COM1_OFFSET;
+
+    for (i = 0; i < UART_MAX_DEVS; i++) {
+        if (ptr[i] == 0) {
+            continue;
+        }
+
+        uart_init(uart_get_dev(i), ptr[i], uart_intrs[i]);
+    }
+}
+
+void __init
+uart_info(void)
+{
+    const struct uart *uart;
+    size_t i;
+
+    for (i = 0; i < ARRAY_SIZE(uart_devs); i++) {
+        uart = uart_get_dev(i);
+
+        if (uart->port != 0) {
+            printf("uart%zu: port:%#x irq:%u\n", i, (unsigned int)uart->port,
+                   (unsigned int)uart->intr);
+        }
+    }
+}