Am 23.08.2013 09:59, schrieb Leon Alrae:
> From: James Hogan <james.ho...@imgtec.com>
>
> Commit a427338 (mips_malta: correct reading MIPS revision at 0x1fc00010)
> altered the behaviour of the monitor flash mapping at the reset address
> by making it read only. However this causes data bus error exceptions
> when it is written to since it is effectively unassigned memory for
> writes. This isn't how the real hardware behaves. That memory can be
> written to (even with the MFWR jumper not fitted) and the new value read
> back from, but it doesn't get written back to the monitor flash so is
> volatile.
>
> This is fixed by converting the bios copy from read only ram to a bios
> device with a nop write callback.
That sounds like a contradiction: The nop write will not have reads
return the new value, will it?
Why not just remove the _set_readonly and have it reloaded on reset for
volatility?
Anyway, having a MemoryRegionOps with just a .write looks dangerous, but
I guess you've tested read to work. We had been seeing assertions
elsewhere when either was missing.
Regards,
Andreas
>
> Signed-off-by: James Hogan <james.ho...@imgtec.com>
> Cc: Paul Burton <paul.bur...@imgtec.com>
> Cc: Leon Alrae <leon.al...@imgtec.com>
> Cc: Aurelien Jarno <aurel...@aurel32.net>
> Signed-off-by: Leon Alrae <leon.al...@imgtec.com>
> ---
> hw/mips/mips_malta.c | 14 ++++++++++++--
> 1 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
> index f8d064c..9e721d3 100644
> --- a/hw/mips/mips_malta.c
> +++ b/hw/mips/mips_malta.c
> @@ -873,6 +873,16 @@ static void cpu_request_exit(void *opaque, int irq, int
> level)
> }
> }
>
> +static void monflash_copy_mem_write(void *opaque, hwaddr ram_addr,
> + uint64_t val, unsigned size)
> +{
> +}
> +
> +static const MemoryRegionOps monflash_copy_mem_ops = {
> + .write = monflash_copy_mem_write,
> + .endianness = DEVICE_NATIVE_ENDIAN,
> +};
> +
> static
> void mips_malta_init(QEMUMachineInitArgs *args)
> {
> @@ -1043,13 +1053,13 @@ void mips_malta_init(QEMUMachineInitArgs *args)
> * handled by an overlapping region as the resulting ROM code subpage
> * regions are not executable.
> */
> - memory_region_init_ram(bios_copy, NULL, "bios.1fc", BIOS_SIZE);
> + memory_region_init_rom_device(bios_copy, NULL, &monflash_copy_mem_ops,
> NULL,
> + "bios.1fc", BIOS_SIZE);
> if (!rom_copy(memory_region_get_ram_ptr(bios_copy),
> FLASH_ADDRESS, BIOS_SIZE)) {
> memcpy(memory_region_get_ram_ptr(bios_copy),
> memory_region_get_ram_ptr(bios), BIOS_SIZE);
> }
> - memory_region_set_readonly(bios_copy, true);
> memory_region_add_subregion(system_memory, RESET_ADDRESS, bios_copy);
>
> /* Board ID = 0x420 (Malta Board with CoreLV) */
>
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