Using mmap against aspeed-lpc-ctrl device - weird bytes :D

[Patrick Venture]

Just to give you some context snippets:

System DTS snippet:

reserved-memory {
 #address-cells = <1>;
 #size-cells = <1>;
 ranges;
 lpc_mapped_memory: region at 98000000 {
  no-map;
  reg = <0x98000000 0x00800000>; /* 8MB */
 };
};

&lpc_ctrl {
 status = "okay";
 memory-region = <&lpc_mapped_memory>;
 flash = <&spi1>; // spi disabled, but needed for lpc_ctrl to probe
};

So, on the BMC, it receives the host's memory map address --> so it
can configure the window:

https://github.com/openbmc/phosphor-ipmi-flash/blob/master/lpc_aspeed.cpp#L42

Then the host tool, mmap's to the host set-aside address, 4KiB, and
tells the BMC to copy out the 4KiB:

https://gerrit.openbmc-project.xyz/c/openbmc/phosphor-ipmi-flash/+/17505

Keep in mind, previously this was working by the BMC opening /dev/mem
and mapping against lpc_mapped_memory -- but now we're opening
aspeed-lpc-ctrl.  In the code above, regionAddress ==
lpc_mapped_memory, and regionSize is 64KiB.

Can you take a look to at least sanity check this?

It ends up copying out data that looks like this:

00000000  0a 00 01 00 0a 00 01 00  0a 00 01 00 0a 00 01 00  |................|
*
00001000

Patrick