From b6181e4a21b1bc3b5615604e175c6a297b661687 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jodersky@gmail.com>
Date: Thu, 3 Apr 2014 18:48:59 +0200
Subject: add uniform io interface

---
 kernel/io/mcu/atmega2560/usart.c | 148 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 kernel/io/mcu/atmega2560/usart.c

(limited to 'kernel/io/mcu/atmega2560/usart.c')

diff --git a/kernel/io/mcu/atmega2560/usart.c b/kernel/io/mcu/atmega2560/usart.c
new file mode 100644
index 0000000..381f403
--- /dev/null
+++ b/kernel/io/mcu/atmega2560/usart.c
@@ -0,0 +1,148 @@
+#include "io/io.h"
+#include "collection/list.h"
+#include "collection/rbuffer.h"
+#include "task/sched.h"
+#include "mcu/io/usart.h"
+#include "mcu/task/context.h"
+#include <avr/interrupt.h>
+#include <avr/io.h>
+
+struct usart_private {
+    char __rx_buffer[USART_BUFFER_SIZE];
+    char __tx_buffer[USART_BUFFER_SIZE];
+
+    struct rbuffer_t rx_buffer;
+    struct rbuffer_t tx_buffer;
+
+    struct list_head rx_queue;
+    struct list_head tx_queue;
+
+    volatile unsigned char* const ucsrxa;
+    volatile unsigned char* const ubrrxh;
+    volatile unsigned char* const ubrrxl;
+    volatile unsigned char* const ucsrxb;
+    char u2xx;
+    char rxenx;
+    char txenx;
+    char rxciex;
+    char udriex;
+};
+
+int usart_open(struct file* usart) {
+    struct usart_private* priv = (struct usart_private*) usart->private_data;
+
+    INIT_LIST_HEAD(&priv->rx_queue);
+    INIT_LIST_HEAD(&priv->tx_queue);
+    INIT_RBUFFER(&priv->rx_buffer, priv->__rx_buffer, USART_BUFFER_SIZE);
+    INIT_RBUFFER(&priv->tx_buffer, priv->__tx_buffer, USART_BUFFER_SIZE);
+
+    return 0;
+}
+
+int usart_ioctl(struct file* usart, int cmd, long args) {
+    struct usart_private* priv = (struct usart_private*) usart->private_data;
+
+    switch (cmd) {
+        case IOCTL_SET_BAUD: {
+            long baud = args;
+            (*priv->ucsrxa) |= (1 << priv->u2xx);
+            long baud_setting = (F_CPU / 4 / baud - 1) / 2;
+            (*priv->ubrrxh) = baud_setting >> 8;
+            (*priv->ubrrxl) = baud_setting;
+            (*priv->ucsrxb) |= (1 << priv->rxenx) | (1 << priv->txenx) | (1 << priv->rxciex);
+            (*priv->ucsrxb) &= ~(1 << priv->udriex);
+            return 0;
+        }
+        default:
+            return -1;
+    }
+}
+
+ssize_t usart_write(struct file* usart, const char* const buffer, size_t length) {
+    struct usart_private* priv = (struct usart_private*) usart->private_data;
+    volatile unsigned char* ucsrxb = (priv->ucsrxb);
+    char write_enable = (1 << priv->udriex);
+
+    ssize_t wrote = 0;
+    int r = 0;
+    do {
+        cli();
+        r = rbuffer_write(&priv->tx_buffer, buffer[wrote]);
+        wrote += 1;
+        sei();
+        *ucsrxb |= write_enable;
+    } while (r == 0 && wrote < length);
+    return wrote;
+}
+
+ssize_t usart_read(struct file* usart, char* const buffer, size_t length) {
+    struct usart_private* priv = (struct usart_private*) usart->private_data;
+    while (rbuffer_empty(&priv->rx_buffer)) {
+        sleep_queue(&priv->rx_queue);
+        yield();
+    }
+    size_t read = 0;
+    size_t r = 0;
+    while (!rbuffer_empty(&priv->rx_buffer) && read < length && r == 0) {
+        cli();
+        r = rbuffer_read(&priv->rx_buffer, buffer + read);
+        read += 1;
+        sei();
+    }
+    return read;
+}
+
+int usart_close(struct file* usart) {
+    return 0;
+}
+
+struct file_operations usart_fops = {
+    .open = usart_open,
+    .ioctl = usart_ioctl,
+    .read = usart_read,
+    .write = usart_write,
+    .close = usart_close
+};
+
+struct usart_private _usart0 = {
+    .ucsrxa = &UCSR0A,
+    .ubrrxh = &UBRR0H,
+    .ubrrxl = &UBRR0L,
+    .ucsrxb = &UCSR0B,
+    .u2xx = U2X0,
+    .rxenx = RXEN0,
+    .txenx = TXEN0,
+    .rxciex = RXCIE0,
+    .udriex = UDRIE0
+};
+
+struct file usart0 = {
+    .fops = &usart_fops,
+    .private_data = &_usart0
+};
+
+//called when data register is empty
+ISR(USART0_UDRE_vect) {
+    struct usart_private* priv = (struct usart_private*) usart0.private_data;
+    char c;
+
+    if (rbuffer_read(&priv->tx_buffer, &c) == 0) {
+        UDR0 = c;
+    } else {
+        UCSR0B &= ~(1 << UDRIE0); //buffer empty, disable interruot
+    }
+}
+
+//called when byte is received
+ISR(USART0_RX_vect, ISR_NAKED) {
+    context_save();
+
+    struct usart_private* priv = (struct usart_private*) usart0.private_data;
+    
+    char c = UDR0;
+    rbuffer_write(&priv->rx_buffer, c);
+    wake_all_queue(&priv->rx_queue);
+
+    context_restore();
+    asm volatile ("reti");
+}
\ No newline at end of file
-- 
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