[PATCH] goldfish_rtc: Add endianness property

[Stafford Horne <shorne@gmail.com>]

Add an endianness property to allow configuring the RTC as either
native, little or big endian.

Cc: Laurent Vivier <lvivier@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Stafford Horne <shorne@gmail.com>
---
In a recent mail thread[0] it was discussed that future users of goldfish devices
should use little-endian rather than native endian.  This is to avoid having to
define special ioread/write routines in the Linux kernel as the default of the
Linux kernel is to use little-endian.

I have defined a property to allow us to make this change the endianness of the
device at initialization time.  For OpenRISC we can now set the qemu device
endianness property to little-endian and the device works.

For now I kept the default as DEVICE_NATIVE_ENDIAN for illustration purposes I
could also do:

 - Add the "endianness" property to all goldfish devices.
 - Switch the default to LITTLE_ENDIAN and just set BIG_ENDIAN for m68k only.
 - Just the bare minimum, using this patch and also set little-endian in
   OpenRISC.
 - Just drop this patch and use BIG_ENDIAN access for goldfish in the kernel for
   OpenRISC like m68k does.

I have tested this with the OpenRISC virt platform[1] available here (now with pci
support).

[0] https://lore.kernel.org/all/CAK8P3a13PTsMExyXZm5sZM3WBK-8hoNFjYoi19pHmKKCJQmHeA@mail.gmail.com/
[1] https://github.com/stffrdhrn/qemu/commits/or1k-virt-2

 hw/rtc/goldfish_rtc.c         | 45 ++++++++++++++++++++++++++++-------
 include/hw/rtc/goldfish_rtc.h |  2 ++
 2 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/hw/rtc/goldfish_rtc.c b/hw/rtc/goldfish_rtc.c
index 35e493be31..ab1e15a3e2 100644
--- a/hw/rtc/goldfish_rtc.c
+++ b/hw/rtc/goldfish_rtc.c
@@ -216,14 +216,34 @@ static int goldfish_rtc_post_load(void *opaque, int version_id)
     return 0;
 }
 
-static const MemoryRegionOps goldfish_rtc_ops = {
-    .read = goldfish_rtc_read,
-    .write = goldfish_rtc_write,
-    .endianness = DEVICE_NATIVE_ENDIAN,
-    .valid = {
-        .min_access_size = 4,
-        .max_access_size = 4
-    }
+static const MemoryRegionOps goldfish_rtc_ops[3] = {
+    [DEVICE_NATIVE_ENDIAN] = {
+        .read = goldfish_rtc_read,
+        .write = goldfish_rtc_write,
+        .endianness = DEVICE_NATIVE_ENDIAN,
+        .valid = {
+            .min_access_size = 4,
+            .max_access_size = 4
+        }
+    },
+    [DEVICE_LITTLE_ENDIAN] = {
+        .read = goldfish_rtc_read,
+        .write = goldfish_rtc_write,
+        .endianness = DEVICE_LITTLE_ENDIAN,
+        .valid = {
+            .min_access_size = 4,
+            .max_access_size = 4
+        }
+    },
+    [DEVICE_BIG_ENDIAN] = {
+        .read = goldfish_rtc_read,
+        .write = goldfish_rtc_write,
+        .endianness = DEVICE_BIG_ENDIAN,
+        .valid = {
+            .min_access_size = 4,
+            .max_access_size = 4
+        }
+    },
 };
 
 static const VMStateDescription goldfish_rtc_vmstate = {
@@ -265,7 +285,8 @@ static void goldfish_rtc_realize(DeviceState *d, Error **errp)
     SysBusDevice *dev = SYS_BUS_DEVICE(d);
     GoldfishRTCState *s = GOLDFISH_RTC(d);
 
-    memory_region_init_io(&s->iomem, OBJECT(s), &goldfish_rtc_ops, s,
+    memory_region_init_io(&s->iomem, OBJECT(s),
+                          &goldfish_rtc_ops[s->endianness], s,
                           "goldfish_rtc", 0x24);
     sysbus_init_mmio(dev, &s->iomem);
 
@@ -274,10 +295,16 @@ static void goldfish_rtc_realize(DeviceState *d, Error **errp)
     s->timer = timer_new_ns(rtc_clock, goldfish_rtc_interrupt, s);
 }
 
+static Property goldfish_rtc_properties[] = {
+    DEFINE_PROP_UINT8("endianness", GoldfishRTCState, endianness, DEVICE_NATIVE_ENDIAN),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void goldfish_rtc_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
+    device_class_set_props(dc, goldfish_rtc_properties);
     dc->realize = goldfish_rtc_realize;
     dc->reset = goldfish_rtc_reset;
     dc->vmsd = &goldfish_rtc_vmstate;
diff --git a/include/hw/rtc/goldfish_rtc.h b/include/hw/rtc/goldfish_rtc.h
index 79ca7daf5d..8e1aeb85e3 100644
--- a/include/hw/rtc/goldfish_rtc.h
+++ b/include/hw/rtc/goldfish_rtc.h
@@ -42,6 +42,8 @@ struct GoldfishRTCState {
     uint32_t irq_pending;
     uint32_t irq_enabled;
     uint32_t time_high;
+
+    uint8_t endianness;
 };
 
 #endif
-- 
2.36.1