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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
