Extract musicpal.c I2C bitbanging code and make it gpio aware

Signed-off-by: Benoit Canet <benoit.canet@gmail.com>
Signed-off-by: Andrzej Zaborowski <balrogg@gmail.com>

1 files changed, 179 insertions, 0 deletions

diff --git a/hw/bitbang_i2c.c b/hw/bitbang_i2c.c
new file mode 100644
index 0000000000..9ab04cc42e
--- /dev/null
+++ b/hw/bitbang_i2c.c
@@ -0,0 +1,179 @@
+/*
+ * Bit-Bang i2c emulation extracted from
+ * Marvell MV88W8618 / Freecom MusicPal emulation.
+ *
+ * Copyright (c) 2008 Jan Kiszka
+ *
+ * This code is licenced under the GNU GPL v2.
+ */
+#include "hw.h"
+#include "i2c.h"
+#include "sysbus.h"
+
+typedef enum bitbang_i2c_state {
+    STOPPED = 0,
+    INITIALIZING,
+    SENDING_BIT7,
+    SENDING_BIT6,
+    SENDING_BIT5,
+    SENDING_BIT4,
+    SENDING_BIT3,
+    SENDING_BIT2,
+    SENDING_BIT1,
+    SENDING_BIT0,
+    WAITING_FOR_ACK,
+    RECEIVING_BIT7,
+    RECEIVING_BIT6,
+    RECEIVING_BIT5,
+    RECEIVING_BIT4,
+    RECEIVING_BIT3,
+    RECEIVING_BIT2,
+    RECEIVING_BIT1,
+    RECEIVING_BIT0,
+    SENDING_ACK
+} bitbang_i2c_state;
+
+typedef struct bitbang_i2c_interface {
+    SysBusDevice busdev;
+    i2c_bus *bus;
+    bitbang_i2c_state state;
+    int last_data;
+    int last_clock;
+    uint8_t buffer;
+    int current_addr;
+    qemu_irq out;
+} bitbang_i2c_interface;
+
+static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
+{
+    if (i2c->current_addr >= 0)
+        i2c_end_transfer(i2c->bus);
+    i2c->current_addr = -1;
+    i2c->state = STOPPED;
+}
+
+static void bitbang_i2c_gpio_set(void *opaque, int irq, int level)
+{
+    bitbang_i2c_interface *i2c = opaque;
+    int data;
+    int clock;
+    int data_goes_up;
+    int data_goes_down;
+    int clock_goes_up;
+    int clock_goes_down;
+
+    /* get pins states */
+    data    = i2c->last_data;
+    clock   = i2c->last_clock;
+
+    if (irq == 0)
+        data = level;
+    if (irq == 1)
+        clock = level;
+
+    /* compute pins changes */
+    data_goes_up    = data == 1 && i2c->last_data == 0;
+    data_goes_down  = data == 0 && i2c->last_data == 1;
+    clock_goes_up   = clock == 1 && i2c->last_clock == 0;
+    clock_goes_down = clock == 0 && i2c->last_clock == 1;
+
+    if (data_goes_up == 0 && data_goes_down == 0 &&
+        clock_goes_up == 0 && clock_goes_down == 0)
+        return;
+
+    if (!i2c)
+        return;
+
+    if ((RECEIVING_BIT7 > i2c->state && i2c->state > RECEIVING_BIT0)
+            || i2c->state == WAITING_FOR_ACK)
+        qemu_set_irq(i2c->out, 0);
+
+    switch (i2c->state) {
+    case STOPPED:
+        if (data_goes_down && clock == 1)
+            i2c->state = INITIALIZING;
+        break;
+
+    case INITIALIZING:
+        if (clock_goes_down && data == 0)
+            i2c->state = SENDING_BIT7;
+        else
+            bitbang_i2c_enter_stop(i2c);
+        break;
+
+    case SENDING_BIT7 ... SENDING_BIT0:
+        if (clock_goes_down) {
+            i2c->buffer = (i2c->buffer << 1) | data;
+            /* will end up in WAITING_FOR_ACK */
+            i2c->state++; 
+        } else if (data_goes_up && clock == 1)
+            bitbang_i2c_enter_stop(i2c);
+        break;
+
+    case WAITING_FOR_ACK:
+        if (clock_goes_down) {
+            if (i2c->current_addr < 0) {
+                i2c->current_addr = i2c->buffer;
+                i2c_start_transfer(i2c->bus, (i2c->current_addr & 0xfe) / 2,
+                                   i2c->buffer & 1);
+            } else
+                i2c_send(i2c->bus, i2c->buffer);
+            if (i2c->current_addr & 1) {
+                i2c->state = RECEIVING_BIT7;
+                i2c->buffer = i2c_recv(i2c->bus);
+            } else
+                i2c->state = SENDING_BIT7;
+        } else if (data_goes_up && clock == 1)
+            bitbang_i2c_enter_stop(i2c);
+        break;
+
+    case RECEIVING_BIT7 ... RECEIVING_BIT0:
+        qemu_set_irq(i2c->out, i2c->buffer >> 7);
+        if (clock_goes_down) {
+            /* will end up in SENDING_ACK */
+            i2c->state++;
+            i2c->buffer <<= 1;
+        } else if (data_goes_up && clock == 1)
+            bitbang_i2c_enter_stop(i2c);
+        break;
+
+    case SENDING_ACK:
+        if (clock_goes_down) {
+            i2c->state = RECEIVING_BIT7;
+            if (data == 0)
+                i2c->buffer = i2c_recv(i2c->bus);
+            else
+                i2c_nack(i2c->bus);
+        } else if (data_goes_up && clock == 1)
+            bitbang_i2c_enter_stop(i2c);
+        break;
+    }
+
+    i2c->last_data = data;
+    i2c->last_clock = clock;
+}
+
+static void bitbang_i2c_init(SysBusDevice *dev)
+{
+    bitbang_i2c_interface *s = FROM_SYSBUS(bitbang_i2c_interface, dev);
+    i2c_bus *bus;
+
+    sysbus_init_mmio(dev, 0x0, 0);
+
+    bus = i2c_init_bus(&dev->qdev, "i2c");
+    s->bus = bus;
+
+    s->last_data = 1;
+    s->last_clock = 1;
+
+    qdev_init_gpio_in(&dev->qdev, bitbang_i2c_gpio_set, 2);
+    qdev_init_gpio_out(&dev->qdev, &s->out, 1);
+}
+
+static void bitbang_i2c_register(void)
+{
+    sysbus_register_dev("bitbang_i2c",
+        sizeof(bitbang_i2c_interface), bitbang_i2c_init);
+}
+
+device_init(bitbang_i2c_register)