i.MX: Add code to emulate i.MX2 watchdog IP block

Add enough code to emulate i.MX2 watchdog IP block so it would be
possible to reboot the machine running Linux Guest.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Marcel Apfelbaum <marcel.apfelbaum@zoho.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-devel@nongnu.org
Cc: qemu-arm@nongnu.org
Cc: yurovsky@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/misc/Makefile.objs

@@ -34,6 +34,7 @@ obj-$(CONFIG_IMX) += imx25_ccm.o
 obj-$(CONFIG_IMX) += imx6_ccm.o
 obj-$(CONFIG_IMX) += imx6_src.o
 obj-$(CONFIG_IMX) += imx7_ccm.o
+obj-$(CONFIG_IMX) += imx2_wdt.o
 obj-$(CONFIG_MILKYMIST) += milkymist-hpdmc.o
 obj-$(CONFIG_MILKYMIST) += milkymist-pfpu.o
 obj-$(CONFIG_MAINSTONE) += mst_fpga.o

hw/misc/imx2_wdt.c

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2018, Impinj, Inc.
+ *
+ * i.MX2 Watchdog IP block
+ *
+ * Author: Andrey Smirnov <andrew.smirnov@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/bitops.h"
+#include "sysemu/watchdog.h"
+
+#include "hw/misc/imx2_wdt.h"
+
+#define IMX2_WDT_WCR_WDA    BIT(5)      /* -> External Reset WDOG_B */
+#define IMX2_WDT_WCR_SRS    BIT(4)      /* -> Software Reset Signal */
+
+static uint64_t imx2_wdt_read(void *opaque, hwaddr addr,
+                              unsigned int size)
+{
+    return 0;
+}
+
+static void imx2_wdt_write(void *opaque, hwaddr addr,
+                           uint64_t value, unsigned int size)
+{
+    if (addr == IMX2_WDT_WCR &&
+        (value & (IMX2_WDT_WCR_WDA | IMX2_WDT_WCR_SRS))) {
+        watchdog_perform_action();
+    }
+}
+
+static const MemoryRegionOps imx2_wdt_ops = {
+    .read  = imx2_wdt_read,
+    .write = imx2_wdt_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl = {
+        /*
+         * Our device would not work correctly if the guest was doing
+         * unaligned access. This might not be a limitation on the
+         * real device but in practice there is no reason for a guest
+         * to access this device unaligned.
+         */
+        .min_access_size = 4,
+        .max_access_size = 4,
+        .unaligned = false,
+    },
+};
+
+static void imx2_wdt_realize(DeviceState *dev, Error **errp)
+{
+    IMX2WdtState *s = IMX2_WDT(dev);
+
+    memory_region_init_io(&s->mmio, OBJECT(dev),
+                          &imx2_wdt_ops, s,
+                          TYPE_IMX2_WDT".mmio",
+                          IMX2_WDT_REG_NUM * sizeof(uint16_t));
+    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->mmio);
+}
+
+static void imx2_wdt_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = imx2_wdt_realize;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static const TypeInfo imx2_wdt_info = {
+    .name          = TYPE_IMX2_WDT,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(IMX2WdtState),
+    .class_init    = imx2_wdt_class_init,
+};
+
+static WatchdogTimerModel model = {
+    .wdt_name = "imx2-watchdog",
+    .wdt_description = "i.MX2 Watchdog",
+};
+
+static void imx2_wdt_register_type(void)
+{
+    watchdog_add_model(&model);
+    type_register_static(&imx2_wdt_info);
+}
+type_init(imx2_wdt_register_type)

include/hw/misc/imx2_wdt.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2017, Impinj, Inc.
+ *
+ * i.MX2 Watchdog IP block
+ *
+ * Author: Andrey Smirnov <andrew.smirnov@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef IMX2_WDT_H
+#define IMX2_WDT_H
+
+#include "hw/sysbus.h"
+
+#define TYPE_IMX2_WDT "imx2.wdt"
+#define IMX2_WDT(obj) OBJECT_CHECK(IMX2WdtState, (obj), TYPE_IMX2_WDT)
+
+enum IMX2WdtRegisters {
+    IMX2_WDT_WCR     = 0x0000,
+    IMX2_WDT_REG_NUM = 0x0008 / sizeof(uint16_t) + 1,
+};
+
+
+typedef struct IMX2WdtState {
+    /* <private> */
+    SysBusDevice parent_obj;
+
+    MemoryRegion mmio;
+} IMX2WdtState;
+
+#endif /* IMX7_SNVS_H */