We've prepared a series of patches (ported to Ubuntu-3.19.0-11.11), which add OpenPower support to the Ubuntu kernel.

The changes are available in the ubuntu/vivid branch of:

 https://github.com/open-power/linux.git

(or I can attach them separately).

Changelogs are as follows:

commit 2f0190bd43764559b250a5bd11aca050f909aa21
Author: Benjamin Herrenschmidt <email address hidden>
Date:   Fri Nov 14 16:13:50 2014 +1100

    powerpc/powernv: Support OPAL requested heartbeat
    
    If OPAL requests it, call it back via opal_poll_events() at a
    regular interval. Some versions of OPAL on some machines require
    this to operate some internal timeouts properly.
    
    Signed-off-by: Benjamin Herrenschmidt <email address hidden>
    
    Backport notes:
     cherry-picked from mpe-next, 3bf57561d4dbd36ba45ce05656b0469bfdcc7ef2
     minor conflicts resolved
    Signed-off-by: Jeremy Kerr <email address hidden>

commit e1c89541e7163494ad091f3c2622649d91ac7597
Author: Benjamin Herrenschmidt <email address hidden>
Date:   Mon Feb 16 14:59:08 2015 +1100

    device: Add dev_of_node() accessor
    
    Suggested by Arnd Bergmann, this gives a practical accessor for
    the of_node field of struct device while instructing the compiler
    that it will be NULL if CONFIG_OF is not set.
    
    Signed-off-by: Benjamin Herrenschmidt <email address hidden>
    Acked-by: Rob Herring <email address hidden>
    
    Backport notes:
     Submission to LKML at: https://patchwork.kernel.org/patch/5831161/
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 2c242b30756f77528516a4e9e986818ac4e90490
Author: Benjamin Herrenschmidt <email address hidden>
Date:   Wed Feb 18 11:25:18 2015 +1100

    drivers/core/of: Add symlink to device-tree from devices with an OF node
    
    So I've been annoyed lately with having a bunch of devices such as i2c
    eeproms (for use by VPDs, server world !) and other bits and pieces that
    I want to be able to identify from userspace, and possibly provide
    additional data about from FW.
    
    Basically, it boils down to correlating the sysfs device with the OF
    tree device node, so that user space can use device-tree info such as
    additional "location" or "label" (or whatever else we can come up with)
    propreties to identify a given device, or get some attributes of use
    about it, etc...
    
    Now, so far, we've done that in some subsystem in a fairly ad-hoc basis
    using "devspec" properties. For example, PCI creates them if it can
    correlate the probed device with a DT node. Some powerpc specific busses
    do that too.
    
    However, i2c doesn't and it would be nice to have something more generic
    since technically any device can have a corresponding device tree node.
    
    This patch adds an "of_node" symlink to devices that have a non-NULL
    dev->of_node pointer, the patch is pretty trivial and seems to work just
    fine for me.
    
    Signed-off-by: Benjamin Herrenschmidt <email address hidden>
    Acked-by: Rob Herring <email address hidden>
    
    Backport notes:
     Submission to LKML at: https://patchwork.kernel.org/patch/5842241/
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 1d9d9bdad2553f39de92eba40f8663eb45819e8c
Author: Michael Ellerman <email address hidden>
Date:   Sat Mar 28 21:35:16 2015 +1100

    powerpc: Add a proper syscall for switching endianness
    
    We currently have a "special" syscall for switching endianness. This is
    syscall number 0x1ebe, which is handled explicitly in the 64-bit syscall
    exception entry.
    
    That has a few problems, firstly the syscall number is outside of the
    usual range, which confuses various tools. For example strace doesn't
    recognise the syscall at all.
    
    Secondly it's handled explicitly as a special case in the syscall
    exception entry, which is complicated enough without it.
    
    As a first step toward removing the special syscall, we need to add a
    regular syscall that implements the same functionality.
    
    The logic is simple, it simply toggles the MSR_LE bit in the userspace
    MSR. This is the same as the special syscall, with the caveat that the
    special syscall clobbers fewer registers.
    
    This version clobbers r9-r12, XER, CTR, and CR0-1,5-7.
    
    Signed-off-by: Michael Ellerman <email address hidden>
    
    Backport notes:
     Cherry-picked (with conflicts resolved) from mpe-next,
     commit 529d235a0e190ded1d21ccc80a73e625ebcad09b
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 352598493e72d80fcf136b5c30add7f9dd32b30a
Author: Cyril Bur <email address hidden>
Date:   Tue Feb 17 18:27:34 2015 +1100

    powerpc/powernv: Add interfaces for flash device access
    
    This change adds the OPAL interface definitions to allow Linux to read,
    write and erase from system flash devices. We register platform devices
    for the flash devices exported by firmware.
    
    We clash with the existing opal_flash_init function, which is really for
    the FSP flash update functionality, so we rename that initcall to
    opal_flash_update_init().
    
    A future change will add an mtd driver that uses this interface.
    
    Changes from Joel Stanley and Jeremy Kerr.
    
    Signed-off-by: Cyril Bur <email address hidden>
    Signed-off-by: Jeremy Kerr <email address hidden>
    Signed-off-by: Joel Stanley <email address hidden>
    
    Backport notes:
     Submission to linuxppc-dev: http://patchwork.ozlabs.org/patch/457095/

commit 1acd5ddde4a50eced6d39381f18126ac94b1ffb7
Author: Cyril Bur <email address hidden>
Date:   Tue Feb 17 18:27:35 2015 +1100

    drivers/mtd: add powernv flash MTD abstraction driver
    
    Powerpc powernv platforms allow access to certain system flash devices
    through a firmwarwe interface. This change adds an mtd driver for these
    flash devices.
    
    Minor updates from Jeremy Kerr and Joel Stanley.
    
    Signed-off-by: Cyril Bur <email address hidden>
    Signed-off-by: Joel Stanley <email address hidden>
    Signed-off-by: Jeremy Kerr <email address hidden>
    
    Backport notes:
     Upstream submission at: http://patchwork.ozlabs.org/patch/457096/

commit 37889e2e1b7fd7576a83cdddca60d2ff81020d24
Author: Neelesh Gupta <email address hidden>
Date:   Wed Feb 11 11:57:23 2015 +0530

    powerpc/powernv: Add OPAL message notifier unregister function
    
    Provide an unregister interface for the opal message notifiers
    to be called when not needed like during driver unload/remove.
    
    Signed-off-by: Neelesh Gupta <email address hidden>
    Reviewed-by: Vasant Hegde <email address hidden>
    Signed-off-by: Benjamin Herrenschmidt <email address hidden>
    
    Backport notes:
     Cherry-picked from mpe-next: b921e90260cec1e04988bb3763491de885b67b51
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 744b9761d910fa26f76b99b21d4a86110bac2db2
Author: Joel Stanley <email address hidden>
Date:   Fri Jan 30 17:13:08 2015 +1030

    powerpc/powernv: Add OPAL soft-poweroff routine
    
    Register a notifier for a OPAL message indicating that the machine
    should prepare itself for a graceful power off.
    
    OPAL will tell us if the power off is a reboot or shutdown, but for now
    we perform the same orderly_poweroff action.
    
    Signed-off-by: Joel Stanley <email address hidden>
    Signed-off-by: Michael Ellerman <email address hidden>
    
    Backport notes:
     Cherry-picked from upstream commit d3f180ea1a44aecba1b0dab2a253428e77f906bf
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 6f4b0f59a9a359bfa859bbb69aed6e50e891f613
Author: Joel Stanley <email address hidden>
Date:   Thu Apr 2 11:18:28 2015 +0800

    drivers/sbus/char/envctrl.c: ignore orderly_poweroff return value
    
    orderly_poweroff() unconditionally returns 0, so remove the dead code that
    checks the return value.
    
    A future patch will change the return type to void.
    
    Signed-off-by: Joel Stanley <email address hidden>
    Acked-by: David S. Miller <email address hidden>
    Cc: Fabian Frederick <email address hidden>
    Cc: Benjamin Herrenschmidt <email address hidden>
    Cc: Michael Ellerman <email address hidden>
    Cc: Rusty Russell <email address hidden>
    Cc: Jeremy Kerr <email address hidden>
    Signed-off-by: Andrew Morton <email address hidden>
    
    Backport notes:
     Queued in -mm tree:
       http://ozlabs.org/~akpm/mmotm/broken-out/envctrl-ignore-orderly_poweroff-return-value.patch
    
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 53cffb522127c3cae82bce12a2434f8ef6f4b1e3
Author: Joel Stanley <email address hidden>
Date:   Thu Apr 2 11:19:22 2015 +0800

    kernel/reboot.c: add orderly_reboot for graceful reboot
    
    The kernel has orderly_poweroff which allows the kernel to initiate a
    graceful shutdown of userspace, by running /sbin/poweroff.  This adds
    orderly_reboot that will cause userspace to shut itself down by calling
    /sbin/reboot.
    
    This will be used for shutdown initiated by a system controller on
    platforms that do not use ACPI.
    
    orderly_reboot() should be used when the system wants to allow userspace
    to gracefully shut itself down.  For cases where the system may imminently
    catch on fire, the existing emergency_restart() provides an immediate
    reboot without involving userspace.
    
    Signed-off-by: Joel Stanley <email address hidden>
    Cc: Fabian Frederick <email address hidden>
    Cc: Benjamin Herrenschmidt <email address hidden>
    Cc: Michael Ellerman <email address hidden>
    Cc: Rusty Russell <email address hidden>
    Cc: Jeremy Kerr <email address hidden>
    Cc: David S. Miller <email address hidden>
    Signed-off-by: Andrew Morton <email address hidden>
    
    Backported notes:
     Taken from -mm tree: http://ozlabs.org/~akpm/mmotm/broken-out/kernel-rebootc-add-orderly_reboot-for-graceful-reboot.patch

commit 63df16447d186fcfa83adecdbd7181551070ffa6
Author: Joel Stanley <email address hidden>
Date:   Thu Apr 2 11:20:19 2015 +0800

    powerpc/powernv: reboot when requested by firmware
    
    Use orderly_reboot so userspace will to shut itself down via the reboot
    path.  This is required for graceful reboot initiated by the BMC, such as
    when a user uses ipmitool to issue a 'chassis power cycle' command.
    
    Signed-off-by: Joel Stanley <email address hidden>
    Acked-by: Michael Ellerman <email address hidden>
    Cc: Fabian Frederick <email address hidden>
    Cc: Benjamin Herrenschmidt <email address hidden>
    Cc: Rusty Russell <email address hidden>
    Cc: Jeremy Kerr <email address hidden>
    Cc: David S. Miller <email address hidden>
    Signed-off-by: Andrew Morton <email address hidden>
    
    Backport notes:
     Taken from -mm tree: http://ozlabs.org/~akpm/mmotm/broken-out/powerpc-powernv-reboot-when-requested-by-firmware.patch
    Signed-off-by: Jeremy Kerr <email address hidden>

commit 8589e12d09d03b03167ce9cb9bc6c7070f3ccd7e
Author: Jeremy Kerr <email address hidden>
Date:   Sat Feb 7 10:02:21 2015 +0800

    powerpc/powernv: Add opal-prd channel
    
    This change adds a char device to access the "PRD" (processor runtime
    diagnostics) channel to OPAL firmware.
    
    Includes contributions from Vaidyanathan Srinivasan, Neelesh Gupta &
    Vishal Kulkarni.
    
    Signed-off-by: Neelesh Gupta <email address hidden>
    Signed-off-by: Jeremy Kerr <email address hidden>
    
    Backport notes:
      Submitted upstream: http://patchwork.ozlabs.org/patch/457097/
      Backport requires the OPAL_MSG_DPO definition
    
    Signed-off-by: Jeremy Kerr <email address hidden>