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

[Patrick Venture]

On Fri, Jan 18, 2019 at 10:38 AM Patrick Venture <venture at google.com> wrote:
>
> 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

Reading the mapping code more closely, I see I'm setting the offset to
the memory window -- this made sense when using /dev/mem, but for
aspeed-lpc-ctrl maybe it should be 0.  Testing that now.

>
> 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