From: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> Commit 3fe9a838ec "dp8393x: Always use 32-bit accesses" set .impl.min_access_size and .impl.max_access_size to 4 to try and fix the Linux jazzsonic driver which uses 32-bit accesses.
The problem with forcing the register access to 32-bit in this way is that since the dp8393x uses 16-bit registers, a manual endian swap is required for devices on big endian machines with 32-bit accesses. For both access sizes and machine endians the QEMU memory API can do the right thing automatically: all that is needed is to set .impl.min_access_size to 2 to declare that the dp8393x implements 16-bit registers. Normally .impl.max_access_size should also be set to 2, however that doesn't quite work in this case since the register stride is specified using a (dynamic) it_shift property which is applied during the MMIO access itself. The effect of this is that for a 32-bit access the memory API performs 2 x 16-bit accesses, but the use of it_shift within the MMIO access itself causes the register value to be repeated in both the top 16-bits and bottom 16-bits. The Linux jazzsonic driver expects the stride to be zero-extended up to access size and therefore fails to correctly detect the dp8393x device due to the extra data in the top 16-bits. The solution here is to remove .impl.max_access_size so that the memory API will correctly zero-extend the 16-bit registers to the access size up to and including it_shift. Since it_shift is never greater than 2 than this will always do the right thing for both 16-bit and 32-bit accesses regardless of the machine endian, allowing the manual endian swap code to be removed. Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> Fixes: 3fe9a838ec ("dp8393x: Always use 32-bit accesses") Message-Id: <20210705214929.17222-2-mark.cave-ayl...@ilande.co.uk> Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> --- hw/net/dp8393x.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/hw/net/dp8393x.c b/hw/net/dp8393x.c index a9224a5bc88..71c82a07c23 100644 --- a/hw/net/dp8393x.c +++ b/hw/net/dp8393x.c @@ -588,15 +588,14 @@ 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); @@ -677,11 +676,16 @@ static void dp8393x_write(void *opaque, hwaddr addr, uint64_t data, } } +/* + * Since .impl.max_access_size is effectively controlled by the it_shift + * property, leave it unspecified for now to allow the memory API to + * correctly zero extend the 16-bit register values to the access size up to and + * including it_shift. + */ 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, .endianness = DEVICE_NATIVE_ENDIAN, }; -- 2.31.1