[PATCH 2/6] dp8393x: don't force 32-bit register access

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

Commit 3fe9a838ec "dp8393x: Always use 32-bit accesses" assumed that all accesses
to the registers were 32-bit but this is actually not the case. The access size is
determined by the CPU instruction used and not the number of physical address lines.

The big_endian workaround applied to the register read/writes was actually caused
by forcing the access size to 32-bit when the guest OS was using a 16-bit access.
Since the registers are 16-bit then we can simply set .impl.min_access to 2 and
then the memory API will automatically do the right thing for both 16-bit accesses
used by Linux and 32-bit accesses used by the MacOS toolbox ROM.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Fixes: 3fe9a838ec ("dp8393x: Always use 32-bit accesses")
Tested-by: Finn Thain <fthain@linux-m68k.org>
Message-Id: <20210625065401.30170-9-mark.cave-ayland@ilande.co.uk>
[PMD: dp8393x_ops.impl.max_access_size 4 -> 2]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/net/dp8393x.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/hw/net/dp8393x.c b/hw/net/dp8393x.c
index 11810c9b600..d16ade2b198 100644
--- a/hw/net/dp8393x.c
+++ b/hw/net/dp8393x.c
@@ -602,15 +602,14 @@ static uint64_t dp8393x_read(void *opaque, hwaddr addr, unsigned int size)
 
     trace_dp8393x_read(reg, reg_names[reg], val, size);
 
-    return s->big_endian ? val << 16 : val;
+    return val;
 }
 
-static void dp8393x_write(void *opaque, hwaddr addr, uint64_t data,
+static void dp8393x_write(void *opaque, hwaddr addr, uint64_t val,
                           unsigned int size)
 {
     dp8393xState *s = opaque;
     int reg = addr >> s->it_shift;
-    uint32_t val = s->big_endian ? data >> 16 : data;
 
     trace_dp8393x_write(reg, reg_names[reg], val, size);
 
@@ -694,8 +693,8 @@ static void dp8393x_write(void *opaque, hwaddr addr, uint64_t data,
 static const MemoryRegionOps dp8393x_ops = {
     .read = dp8393x_read,
     .write = dp8393x_write,
-    .impl.min_access_size = 4,
-    .impl.max_access_size = 4,
+    .impl.min_access_size = 2,
+    .impl.max_access_size = 2,
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
-- 
2.31.1