[Qemu-devel] [PULL 11/30] hw/arm: make bitbanded IO optional on ARMv7-M

[Peter Maydell]

From: Stefan Hajnoczi <address@hidden>

Some ARM CPUs have bitbanded IO, a memory region that allows convenient
bit access via 32-bit memory loads/stores.  This eliminates the need for
read-modify-update instruction sequences.

This patch makes this optional feature an ARMv7MState qdev property,
allowing boards to choose whether they want bitbanding or not.

Status of boards:
 * iotkit (Cortex M33), no bitband
 * mps2 (Cortex M3), bitband
 * msf2 (Cortex M3), bitband
 * stellaris (Cortex M3), bitband
 * stm32f205 (Cortex M3), bitband

As a side-effect of this patch, Peter Maydell noted that the Ethernet
controller on mps2 board is now accessible.  Previously they were hidden
by the bitband region (which does not exist on the real board).

Signed-off-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Message-id: address@hidden
Signed-off-by: Peter Maydell <address@hidden>
---
 include/hw/arm/armv7m.h |  2 ++
 hw/arm/armv7m.c         | 37 ++++++++++++++++++++-----------------
 hw/arm/mps2.c           |  1 +
 hw/arm/msf2-soc.c       |  1 +
 hw/arm/stellaris.c      |  1 +
 hw/arm/stm32f205_soc.c  |  1 +
 6 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/include/hw/arm/armv7m.h b/include/hw/arm/armv7m.h
index 78308d14846..2ba24953b63 100644
--- a/include/hw/arm/armv7m.h
+++ b/include/hw/arm/armv7m.h
@@ -43,6 +43,7 @@ typedef struct {
  *   devices will be automatically layered on top of this view.)
  * + Property "idau": IDAU interface (forwarded to CPU object)
  * + Property "init-svtor": secure VTOR reset value (forwarded to CPU object)
+ * + Property "enable-bitband": expose bitbanded IO
  */
 typedef struct ARMv7MState {
     /*< private >*/
@@ -63,6 +64,7 @@ typedef struct ARMv7MState {
     MemoryRegion *board_memory;
     Object *idau;
     uint32_t init_svtor;
+    bool enable_bitband;
 } ARMv7MState;
 
 #endif
diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index 6b076660574..878613994d2 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -211,25 +211,27 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
     memory_region_add_subregion(&s->container, 0xe000e000,
                                 sysbus_mmio_get_region(sbd, 0));
 
-    for (i = 0; i < ARRAY_SIZE(s->bitband); i++) {
-        Object *obj = OBJECT(&s->bitband[i]);
-        SysBusDevice *sbd = SYS_BUS_DEVICE(&s->bitband[i]);
+    if (s->enable_bitband) {
+        for (i = 0; i < ARRAY_SIZE(s->bitband); i++) {
+            Object *obj = OBJECT(&s->bitband[i]);
+            SysBusDevice *sbd = SYS_BUS_DEVICE(&s->bitband[i]);
 
-        object_property_set_int(obj, bitband_input_addr[i], "base", &err);
-        if (err != NULL) {
-            error_propagate(errp, err);
-            return;
-        }
-        object_property_set_link(obj, OBJECT(s->board_memory),
-                                 "source-memory", &error_abort);
-        object_property_set_bool(obj, true, "realized", &err);
-        if (err != NULL) {
-            error_propagate(errp, err);
-            return;
-        }
+            object_property_set_int(obj, bitband_input_addr[i], "base", &err);
+            if (err != NULL) {
+                error_propagate(errp, err);
+                return;
+            }
+            object_property_set_link(obj, OBJECT(s->board_memory),
+                                     "source-memory", &error_abort);
+            object_property_set_bool(obj, true, "realized", &err);
+            if (err != NULL) {
+                error_propagate(errp, err);
+                return;
+            }
 
-        memory_region_add_subregion(&s->container, bitband_output_addr[i],
-                                    sysbus_mmio_get_region(sbd, 0));
+            memory_region_add_subregion(&s->container, bitband_output_addr[i],
+                                        sysbus_mmio_get_region(sbd, 0));
+        }
     }
 }
 
@@ -239,6 +241,7 @@ static Property armv7m_properties[] = {
                      MemoryRegion *),
     DEFINE_PROP_LINK("idau", ARMv7MState, idau, TYPE_IDAU_INTERFACE, Object *),
     DEFINE_PROP_UINT32("init-svtor", ARMv7MState, init_svtor, 0),
+    DEFINE_PROP_BOOL("enable-bitband", ARMv7MState, enable_bitband, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/arm/mps2.c b/hw/arm/mps2.c
index c3946da3173..0a0ae867d9b 100644
--- a/hw/arm/mps2.c
+++ b/hw/arm/mps2.c
@@ -186,6 +186,7 @@ static void mps2_common_init(MachineState *machine)
         g_assert_not_reached();
     }
     qdev_prop_set_string(armv7m, "cpu-type", machine->cpu_type);
+    qdev_prop_set_bit(armv7m, "enable-bitband", true);
     object_property_set_link(OBJECT(&mms->armv7m), OBJECT(system_memory),
                              "memory", &error_abort);
     object_property_set_bool(OBJECT(&mms->armv7m), true, "realized",
diff --git a/hw/arm/msf2-soc.c b/hw/arm/msf2-soc.c
index dbefade644d..2702e90b453 100644
--- a/hw/arm/msf2-soc.c
+++ b/hw/arm/msf2-soc.c
@@ -117,6 +117,7 @@ static void m2sxxx_soc_realize(DeviceState *dev_soc, Error 
**errp)
     armv7m = DEVICE(&s->armv7m);
     qdev_prop_set_uint32(armv7m, "num-irq", 81);
     qdev_prop_set_string(armv7m, "cpu-type", s->cpu_type);
+    qdev_prop_set_bit(armv7m, "enable-bitband", true);
     object_property_set_link(OBJECT(&s->armv7m), OBJECT(get_system_memory()),
                                      "memory", &error_abort);
     object_property_set_bool(OBJECT(&s->armv7m), true, "realized", &err);
diff --git a/hw/arm/stellaris.c b/hw/arm/stellaris.c
index dc521b4a5a8..6c69ce79b20 100644
--- a/hw/arm/stellaris.c
+++ b/hw/arm/stellaris.c
@@ -1304,6 +1304,7 @@ static void stellaris_init(MachineState *ms, 
stellaris_board_info *board)
     nvic = qdev_create(NULL, TYPE_ARMV7M);
     qdev_prop_set_uint32(nvic, "num-irq", NUM_IRQ_LINES);
     qdev_prop_set_string(nvic, "cpu-type", ms->cpu_type);
+    qdev_prop_set_bit(nvic, "enable-bitband", true);
     object_property_set_link(OBJECT(nvic), OBJECT(get_system_memory()),
                                      "memory", &error_abort);
     /* This will exit with an error if the user passed us a bad cpu_type */
diff --git a/hw/arm/stm32f205_soc.c b/hw/arm/stm32f205_soc.c
index c486d06a8b0..980e5af13c5 100644
--- a/hw/arm/stm32f205_soc.c
+++ b/hw/arm/stm32f205_soc.c
@@ -109,6 +109,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, 
Error **errp)
     armv7m = DEVICE(&s->armv7m);
     qdev_prop_set_uint32(armv7m, "num-irq", 96);
     qdev_prop_set_string(armv7m, "cpu-type", s->cpu_type);
+    qdev_prop_set_bit(armv7m, "enable-bitband", true);
     object_property_set_link(OBJECT(&s->armv7m), OBJECT(get_system_memory()),
                                      "memory", &error_abort);
     object_property_set_bool(OBJECT(&s->armv7m), true, "realized", &err);
-- 
2.18.0