On Sat, Apr 21, 2012 at 10:20, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> 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 -- geert@xxxxxxxxxxxxxx
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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