Re: [Qemu-devel] [PATCH] pflash_cfi01/pflash_cfi02: convert to memory API

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Sun, Aug 28, 2011 at 06:43:36PM +0300, Avi Kivity wrote:
> cfi02 is annoying in that is ignores some address bits; we probably
> want explicit support in the memory API for that.
> 
> In order to get the correct opaque into the MemoryRegion object, the
> allocation scheme is changed so that the flash emulation code allocates
> memory, instead of the caller.  This clears a FIXME in the flash code.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
> 
> This is a rework of the pflash conversion to the memory API.  It has changed
> significantly - the change in allocation described above - so please review
> carefully.
> 
> The mips_malta change also changes behavious - previously on of the two
> aliases was mapped as rom/device while the other was mapped as plain rom.
> Now both aliases are mapped as rom/device.  I'm guessing that this is the
> right behaviour, and the old behaviour was just an implementation limitation,
> but if someone can check, that would be even better.  That file has the most
> sensitive changes so please review it extra carefully.

Regarding the flash mapping, your description matches my understanding of it.
There is a difference between the 0x1fc and the 0x1e0 mappings though, in that
reading from 0x1fc00010 does not map to the flash but instead gets decoded
into a read from a revision register. To read from the flash at 0x10, you
need to go via the 0x1e0 mapping.

That was never modelled by QEMU, instead the malta board writes into the
backing ram of the flash area, see:
/* Board ID = 0x420 (Malta Board with CoreLV)
   XXX: theoretically 0x1e000010 should map to flash and 0x1fc00010 should
   map to the board ID. */
stl_p(memory_region_get_ram_ptr(bios) + 0x10, 0x00000420);

I assume this will continue to work even after your changes but it would be
good to test it. I can check it.

A problem, with my compiler I see this:
qemu/hw/mips_malta.c: In function ‘mips_malta_init’:
qemu/hw/mips_malta.c:860:37: error: ‘bios’ may be used uninitialized in this function [-Werror=uninitialized]

Cheers