Re: [PATCH] b44: power down PHY when interface down

On Sun, Jul 01, 2007 at 12:23:16PM +0200, Michael Buesch wrote:

quoted

More or less.  You can't add the resistances like that, since the
bus isolation chip buffers the IDSEL signal, but it is correct that
if the host's IDSEL resistor is larger than a certain value, the
combination of the resistive coupling of IDSEL plus the extra buffer
in the isolator might be causing the IDSEL input on the 'guest' PCI
board to assert too late (or not assert at all), causing config
accesses to fail.

(This also depends on the specific 'guest' PCI board used, as you
noted, due to differing IDSEL trace lengths/capacitances and input
pin capacitances on different PCI boards.  Also, it might work at
33 MHz but not work at 66 MHz, etc.)

It doesn't work on any of my boards :(

What extender board is this?  Do you have docs/schematics?
And what motherboard brand/type?

quoted

If you feel adventurous, you could try to hack around this by
figuring out which AD[31:16] line this PCI slot's IDSEL line is
resistively coupled to (depends on the slot), and then adding
another parallel resistor on the board itself to make the bus
isolator's input buffer charge faster.  Note that this does
increase the load on that specific AD[] line, which might cause
other funny effects.

Well, but how to find out to which address line it's connected to?
Pretty hard to follow the PCB traces, especially since it's
multilayered.

Actually, the IDSEL resistor would be on the computer's
motherboard, not on the PCI board.  And to which address line
the IDSEL line is connected depends on which PCI slot on the
motherboard you're looking at.

A multimeter should do the trick, but I would advise against this
if you're not totally comfortable with hacking hardware.