On 11/8/24 16:43, Philippe Mathieu-Daudé wrote:
The Xilinx 'ethlite' device was added in commit b43848a100 ("xilinx: Add ethlite emulation"), being only built back then for a big-endian MicroBlaze target (see commit 72b675caac "microblaze: Hook into the build-system").
I/O endianness access was then clarified in commit d48751ed4f ("xilinx-ethlite: Simplify byteswapping to/from brams"). Here the 'fix' was to use tswap32(). Since the machine was built as big-endian target, tswap32() use means the fix was for a little endian host. While the datasheet (reference added in file header) is not precise about it, we interpret such change as the device expects accesses in big-endian order.
Instead of having a double swapping, one in the core memory layer due to DEVICE_NATIVE_ENDIAN and a second one with the tswap calls, allow the machine code to select the proper endianness desired, removing the need of tswap().
Replace the DEVICE_NATIVE_ENDIAN MemoryRegionOps by a pair of DEVICE_LITTLE_ENDIAN / DEVICE_BIG_ENDIAN. Add the "little-endian" property to select the device endianness, defaulting to little endian. Set the proper endianness on the single machine using the device.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> --- RFC until I digest Paolo's review from v1: https://lore.kernel.org/qemu-devel/34f6fe2f-06e0-4e2a-a361-2d662f6814b5@redh...
tl;dr: this works but would break migration compatibility with the previous version. If you want to keep that, you need to add
- r = tswap32(s->regs[addr]); + r = s->regs[addr];
if (s->little_endian_model) r = cpu_to_le32(r); else r = cpu_to_be32(r);
@@ -161,23 +165,26 @@ eth_write(void *opaque, hwaddr addr, break;
default:
if (s->little_endian_model) r = le32_to_cpu(r); else r = be32_to_cpu(r);
- s->regs[addr] = tswap32(value); + s->regs[addr] = value; break;
These pairs ensure that RAM goes through an even number of swaps. I don't think they are needed but you decide. However, I am wondering if the double MemoryRegionOps are needed *at all*. Since petalogix is arguably a little-endian only machine, can you just use DEVICE_LITTLE_ENDIAN? Paolo