On Sat, Apr 21, 2012 at 10:20, Geert Uytterhoeven <[email protected]> wrote:
>> I've had a look at the NetUSBee docs and see that the USB part of it does
>> require 8 bit writes but little endian 16 bit reads. So we will need to
>> retain the 16 bit reads for potential USB support there.
>
> OK. But you ain't gonna get the right 16 bits using
>
> #define rom_in_be16(addr) \
> ({ u16 __v = (*(__force volatile u16 *) (addr)); __v >>= 8; __v; })
> #define rom_in_le16(addr) \
> ({ u16 __v = le16_to_cpu(*(__force volatile u16 *) (addr));
> __v >>= 8; __v; })
>
> as they both do a 16-bit read and shift the result.
> Perhaps it should just be a 32-bit read instead?
> Are the schematics publicly available?
I found netusbee.zip.
Unfortunately I (my computer) can't grok the schematics files.
However, program_spec.txt says (a.o., I encourage all interested
parties to read it in full):
| USB Data Reads
| ==============
|
| Data Reads from USB are done at base address 0xFA8000 (activating a read
| cycle) as a 16bit word. Data appears on D8-15 as most significant byte, and
| D0-7 as least significant byte. Notice how A15 has to be set to 1 to make it
| a USB cycle.
So inw() should just do a 16-bit big-endian read.
| USB Data Writes
| ===============
|
| Data reads at base address 0xFB8000 actually cause data to be written. As
| the write interface is only 8 bits wide, the 16bits of data must be passed
| through this "8 bit window". The Least Signifant Byte is transferred first
| by left shifting data once and added to 0xFA8000. This is followed by the
| Most significant byte, transferred by left shifting data once and then added
| to 0xFB8000. On this last cycle is where the transfer is actually done.
| Notice how A15 has to be set to 1 to make it a USB cycle.
So outw() should do 2 byte reads.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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