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    SubjectJMB363 false hotplug detections (was: ahci: AHCI and RAID mode SATA patch for Intel Cougar Point DeviceIDs)
    From
    On Sat, Jan 16, 2010 at 12:02 PM, Krzysztof Halasa <khc@pm.waw.pl> wrote:
    > Robert Hancock <hancockrwd@gmail.com> writes:
    >
    >> Hmm.. From those test results I really suspect some kind of hardware
    >> fault. Could be a defective motherboard - I don't know if that chip
    >> needs any terminating resistors on the motherboard for the SATA signal
    >> lines or something, if so, could be they weren't installed properly..
    >
    > Unfortunately I can't find a JMB363 datasheet on the net, but there is
    > a certain mb (p965t-a) schematic available.
    > It seems JMB363 doesn't need terminators on SATA RX/TX lines, there is
    > capacitative coupling only (10 nF in each line).
    >
    > The port in question (SATA#2) on my mb (P45 Neo2) uses pins 56 (RXP)
    > 57 (RXN) and 60 (TXN) 61 (TXP). No visible irregularity, the traces look
    > like they should, go straigt to the capacitors, and then to 0R R-packs
    > and to the connector. It looks exactly the same for both ports. There is
    > no short circuit past the capacitors (from the connector side). I'd say
    > quite low probability that there is something wrong with these signals.
    >
    > It seems the chip uses extra 12k resistors for SATA (p965t-a calls the
    > pins SJ_REXT[12]), pin 44 for port#1 and 55 for port#2. Both look sane.
    > I will check the suspected connections with the machine powered off
    > later.
    >
    > The RX and TX trace pairs go next to each other for up to 10 mm, could
    > that be a problem at these frequencies? If so it would show up on
    > all/many such boards certainly? Can't find any report.
    >
    > OTOH other people have similar problems with other boards: e.g.
    > ASUS P5KC: http://ubuntuforums.org/showthread.php?t=766217
    >           https://bugs.launchpad.net/ubuntu/+source/linux/+bug/377633
    >
    > (unknown boards)
    > https://archlinux-fr.org/doku.php?id=securisation:logcheck
    > http://forum.ubuntu-fr.org/viewtopic.php?pid=2739616
    > http://ubuntu-ky.ubuntuforums.org/showthread.php?p=7243061
    > The last one claims:
    > this started after an upgrade to ubuntu 9.04 and is stll here after re-installing
    > ubuntu 8.10.
    > this was fixed by re-installing ubuntu 8.10 only using the kernal,
    > 2.6.27-7-generic.
    > I don't know if JMB36x is involved in this case, and how reliable the
    > info is.
    >
    > Investigating as time permits.

    Well, it is possible there is some kind of flaw in the JMB363 chip
    itself that causes this problem. (Could be it happens in Windows too,
    I don't think Windows drivers normally report these kinds of events
    anywhere and if it never reached the point of actually deciding a
    device was connected, you likely wouldn't notice.) I suppose we could
    add a workaround in the driver to ignore hotplug events, but then real
    hotplug events wouldn't get handled properly..

    What revision does your JMB363 report in lspci? Mine shows:

    03:00.0 SATA controller: JMicron Technologies, Inc. 20360/20363 Serial
    ATA Controller (rev 03) (prog-if 01 [AHCI 1.0])

    Tejun, any other ideas?
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