[Qemu-devel] [PATCH] integrator: fix Linux boot failure by emulating dbg

[alex.bennee@linaro.org]

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From: Alex Bennée <alex@bennee.com>

Commit 9b8c69243 broke the ability to boot the kernel as the value
returned by unassigned_mem_read returned non-zero and left the kernel
looping forever waiting for it to change (see integrator_led_set in
the kernel code).

Relying on a varying implementation detail is incorrect anyway so this
introduces a memory region to emulate the debug/led region on the
integrator board. It is currently a basic stub as I have no idea what the
behaviour of this region should be so for now it simply returns 0's as
the old unassigned_mem_read did.
---
 hw/arm/integratorcp.c |  2 ++
 hw/misc/Makefile.objs |  1 +
 hw/misc/arm_intdbg.c  | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)
 create mode 100644 hw/misc/arm_intdbg.c

diff --git a/hw/arm/integratorcp.c b/hw/arm/integratorcp.c
index 2ef93ed..e5d07c4 100644
--- a/hw/arm/integratorcp.c
+++ b/hw/arm/integratorcp.c
@@ -446,6 +446,7 @@ static void icp_control_init(hwaddr base)
 }
 
 
+
 /* Board init.  */
 
 static struct arm_boot_info integrator_binfo = {
@@ -508,6 +509,7 @@ static void integratorcp_init(QEMUMachineInitArgs *args)
     icp_control_init(0xcb000000);
     sysbus_create_simple("pl050_keyboard", 0x18000000, pic[3]);
     sysbus_create_simple("pl050_mouse", 0x19000000, pic[4]);
+    sysbus_create_simple("integrator_dbg", 0x1a000000, 0);
     sysbus_create_varargs("pl181", 0x1c000000, pic[23], pic[24], NULL);
     if (nd_table[0].used)
         smc91c111_init(&nd_table[0], 0xc8000000, pic[27]);
diff --git a/hw/misc/Makefile.objs b/hw/misc/Makefile.objs
index 2578e29..e2c84a3 100644
--- a/hw/misc/Makefile.objs
+++ b/hw/misc/Makefile.objs
@@ -22,6 +22,7 @@ obj-$(CONFIG_LINUX) += vfio.o
 endif
 
 obj-$(CONFIG_REALVIEW) += arm_sysctl.o
+obj-y += arm_intdbg.o
 obj-$(CONFIG_A9SCU) += a9scu.o
 obj-$(CONFIG_NSERIES) += cbus.o
 obj-$(CONFIG_ECCMEMCTL) += eccmemctl.o
diff --git a/hw/misc/arm_intdbg.c b/hw/misc/arm_intdbg.c
new file mode 100644
index 0000000..1f21447
--- /dev/null
+++ b/hw/misc/arm_intdbg.c
@@ -0,0 +1,90 @@
+/*
+ * LED, Switch and Debug control registers for ARM Integrator Boards
+ *
+ * This currently is a stub for this functionality written with
+ * reference to what the Linux kernel looks at. Previously we relied
+ * on the behaviour of unassigned_mem_read() in the core.
+ *
+ * Written by Alex Bennée
+ *
+ * This code is licensed under the GPL.
+ */
+
+#include "hw/hw.h"
+#include "hw/sysbus.h"
+#include "exec/address-spaces.h"
+
+#define TYPE_ARM_INTDBG "integrator_dbg"
+#define ARM_INTDBG(obj) \
+    OBJECT_CHECK(arm_intdbg_state, (obj), TYPE_ARM_INTDBG)
+
+typedef struct {
+    SysBusDevice parent_obj;
+    MemoryRegion iomem;
+
+    uint32_t alpha;
+    uint32_t leds;
+    uint32_t switches;
+} arm_intdbg_state;
+
+static uint64_t dbg_control_read(void *opaque, hwaddr offset,
+                                 unsigned size)
+{
+    switch (offset >> 2) {
+    case 0: /* ALPHA */
+        return 0;
+    case 1: /* LEDS */
+        return 0;
+    case 2: /* SWITCHES */
+        return 0;
+    default:
+        hw_error("dbg_control_read: Bad offset %x\n", (int)offset);
+        return 0;
+    }
+}
+
+static void dbg_control_write(void *opaque, hwaddr offset,
+                              uint64_t value, unsigned size)
+{
+    switch (offset >> 2) {
+    case 1: /* ALPHA */
+    case 2: /* LEDS */
+    case 3: /* SWITCHES */
+        /* Nothing interesting implemented yet.  */
+        break;
+    default:
+        hw_error("dbg_control_write: Bad offset %x\n", (int)offset);
+    }
+}
+
+static const MemoryRegionOps dbg_control_ops = {
+    .read = dbg_control_read,
+    .write = dbg_control_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+};
+
+static void dbg_control_init(Object *obj)
+{
+    SysBusDevice *sd = SYS_BUS_DEVICE(obj);
+    arm_intdbg_state *s = ARM_INTDBG(obj);
+    memory_region_init_io(&s->iomem, NULL, &dbg_control_ops, NULL, "dbgleds", 0x1000);
+    sysbus_init_mmio(sd, &s->iomem);
+}
+
+/*
+  Hardware boilerplate
+*/
+
+static const TypeInfo arm_intdbg_info = {
+    .name          = TYPE_ARM_INTDBG,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(arm_intdbg_state),
+    .instance_init = dbg_control_init,
+};
+
+static void arm_intdbg_register_types(void)
+{
+    type_register_static(&arm_intdbg_info);
+}
+
+type_init(arm_intdbg_register_types)
-- 
1.8.4