Initial commit

1 files changed, 190 insertions, 0 deletions

diff --git a/src/uart.c b/src/uart.c
new file mode 100644
index 0000000..eed7fe4
--- /dev/null
+++ b/src/uart.c
@@ -0,0 +1,190 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ * Copyright (c) 2017 Jerko Lenstra.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include <lib/cbuf.h>
+#include <lib/macros.h>
+
+#include "cpu.h"
+#include "error.h"
+#include "io.h"
+#include "uart.h"
+#include "thread.h"
+
+#define UART_BAUD_RATE          115200
+
+#define UART_CLOCK              115200
+#define UART_DIVISOR            (UART_CLOCK / UART_BAUD_RATE)
+
+#define UART_IRQ                4
+
+#define UART_IER_DATA           0x1
+
+#define UART_LCR_8BITS          0x3
+#define UART_LCR_STOP1          0
+#define UART_LCR_PARITY_NONE    0
+#define UART_LCR_DLAB           0x80
+
+#define UART_LSR_DATA_READY     0x01
+#define UART_LSR_TX_EMPTY       0x20
+
+#define UART_COM1_PORT          0x3F8
+#define UART_REG_DAT            0
+#define UART_REG_DIVL           0
+#define UART_REG_IER            1
+#define UART_REG_DIVH           1
+#define UART_REG_LCR            3
+#define UART_REG_LSR            5
+
+#define UART_BUFFER_SIZE        16
+
+#if !ISP2(UART_BUFFER_SIZE)
+#error "invalid buffer size"
+#endif
+
+/*
+ * Data shared between threads and the interrupt handler.
+ *
+ * Interrupts and preemption must be disabled when accessing these data.
+ */
+static uint8_t uart_buffer[UART_BUFFER_SIZE];
+static struct cbuf uart_cbuf;
+static struct thread *uart_waiter;
+
+static void
+uart_irq_handler(void *arg)
+{
+    uint8_t byte;
+    int error;
+    bool spurious;
+
+    (void)arg;
+
+    spurious = true;
+
+    for (;;) {
+        byte = io_read(UART_COM1_PORT + UART_REG_LSR);
+
+        if (!(byte & UART_LSR_DATA_READY)) {
+            break;
+        }
+
+        spurious = false;
+        byte = io_read(UART_COM1_PORT + UART_REG_DAT);
+        error = cbuf_pushb(&uart_cbuf, byte, false);
+
+        if (error) {
+            printf("uart: error: buffer full\n");
+            break;
+        }
+    }
+
+    if (!spurious) {
+        thread_wakeup(uart_waiter);
+    }
+}
+
+void
+uart_setup(void)
+{
+    cbuf_init(&uart_cbuf, uart_buffer, sizeof(uart_buffer));
+
+    io_write(UART_COM1_PORT + UART_REG_LCR, UART_LCR_DLAB);
+    io_write(UART_COM1_PORT + UART_REG_DIVL, UART_DIVISOR);
+    io_write(UART_COM1_PORT + UART_REG_DIVH, UART_DIVISOR >> 8);
+    io_write(UART_COM1_PORT + UART_REG_LCR, UART_LCR_8BITS | UART_LCR_STOP1
+                                            | UART_LCR_PARITY_NONE);
+    io_write(UART_COM1_PORT + UART_REG_IER, UART_IER_DATA);
+
+    cpu_irq_register(UART_IRQ, uart_irq_handler, NULL);
+}
+
+static void
+uart_tx_wait(void)
+{
+    uint8_t byte;
+
+    for (;;) {
+        byte = io_read(UART_COM1_PORT + UART_REG_LSR);
+
+        if (byte & UART_LSR_TX_EMPTY) {
+            break;
+        }
+    }
+}
+
+static void
+uart_write_byte(uint8_t byte)
+{
+    uart_tx_wait();
+    io_write(UART_COM1_PORT + UART_REG_DAT, byte);
+}
+
+void
+uart_write(uint8_t byte)
+{
+    if (byte == '\n') {
+        uart_write_byte('\r');
+    }
+
+    uart_write_byte(byte);
+}
+
+int
+uart_read(uint8_t *byte)
+{
+    int eflags, error;
+
+    thread_preempt_disable();
+    eflags = cpu_intr_save();
+
+    if (uart_waiter) {
+        error = ERROR_BUSY;
+        goto out;
+    }
+
+    for (;;) {
+        error = cbuf_popb(&uart_cbuf, byte);
+
+        if (!error) {
+            break;
+        }
+
+        uart_waiter = thread_self();
+        thread_sleep();
+        uart_waiter = NULL;
+    }
+
+    error = 0;
+
+out:
+    cpu_intr_restore(eflags);
+    thread_preempt_enable();
+
+    return error;
+}