Pierre Ossman wrote: > On Tue, 07 Aug 2007 13:55:59 +0100 > David Vrabel <[EMAIL PROTECTED]> wrote: > >> sdio: disable CD resistor >> >> Disable the card detect resistor to ensure all data lines are equally >> loaded. Not doing this can have a negative impact on buses with >> marginal signal quality. >> >> Signed-off-by: David Vrabel <[EMAIL PROTECTED]> > > I'm not sure about this. I've seen several hosts which lack a > mechanical detect switch.
If host is correctly designed it will have identical pull-ups on all the DAT lines, and therefore this internal pull-up should be disconnected. However, given that disabling the pull-up may cause 4 bit transfers to fail on hardware that omits a host-side pull-up on DAT3 I agree that the resistor should remain enabled. Is there an example driver for a host that uses pin 1/DAT3 sensing for card detection? I'm curious about how removal detections work. App Note on card detection goes into the use of this resistor in more detail but I don't believe this document is publicly available :(. David -- David Vrabel, Software Engineer, Drivers group Tel: +44 (0)1223 692562 CSR plc, Churchill House, Cambridge Business Park, Cowley Road, CB4 0WZ . - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/