regulator issues with 2.6.31 vs 2.6.28 with the same patchset

Can someone explain what the consequences of this bug are?

We don't know that this is an issue. However this could be why we are still having issues with the RTC. It's just very suspicious.

What I've found out so far is all the regulators are failing to properly initialise. I'm looking into why.

The regulators are basically power supplies. The regulator framework abstracts away the control the these power supplies. It allows us to switch off power supplies when a particular device is not in use (to save power).

If the regulators are not initialised, the connected peripheral won't work. (serious)
If the regulators are not powered off, we will consume more power.
If the regulators are configured incorrectly (incorrect voltage), the peripheral might not be able to operate and maximum capacity or behave erratically.

IOW, this needs to be fixed.

With the current in archive kernel I was getting:
root@babbage20:~# dmesg |grep regu
regulator: core version 0.5
mxc_dvfs_core_probe: failed to get gp regulator
mxc_cpufreq_driver_init: failed to get gp regulator
regulator: get() with no identifier
regulator: get() with no identifier
regulator: get() with no identifier

With Brad's test kernel at http://kernel.ubuntu.com/~bradf/linux-image-2.6.31-104-imx51_2.6.31-104.14_armel.deb I get:
lool@babbage20:~$ dmesg |grep regulator
regulator: core version 0.5
Initializing regulators for Babbage.
regulator: SW1: 600 <--> 1375 mV
regulator: SW2: 900 <--> 1850 mV
regulator: SW3: 1100 <--> 1850 mV
regulator: SW4: 1100 <--> 1850 mV
regulator: SWBST: 0 mV
regulator: VIOHI: 0 mV
regulator: VPLL: 1050 <--> 1800 mV
regulator: VDIG: 1050 <--> 1800 mV
regulator: VSD: 1800 <--> 3150 mV
regulator: VUSB2: 2400 <--> 2775 mV
regulator: VVIDEO: 2775 mV
regulator: VAUDIO: 2300 <--> 3000 mV
regulator: VCAM: 2500 <--> 3000 mV fast normal
regulator: VGEN1: 1200 <--> 3150 mV
regulator: VGEN2: 1200 <--> 3150 mV
regulator: VGEN3: 1800 <--> 2900 mV
regulator: VUSB: 0 mV
regulator: GPO1: 0 mV
regulator: GPO2: 0 mV
regulator: GPO3: 0 mV
regulator: GPO4: 0 mV
mxc_dvfs_core_probe: failed to get gp regulator
mxc_cpufreq_driver_init: failed to get gp regulator
regulator: get() with no identifier
regulator: get() with no identifier
regulator: get() with no identifier
regulator_init_complete: incomplete constraints, leaving GPO4 on
regulator_init_complete: incomplete constraints, leaving GPO3 on
regulator_init_complete: incomplete constraints, leaving GPO2 on
regulator_init_complete: incomplete constraints, leaving GPO1 on
regulator_init_complete: incomplete constraints, leaving VUSB on
regulator_init_complete: incomplete constraints, leaving VGEN3 on
regulator_init_complete: incomplete constraints, leaving VGEN2 on
regulator_init_complete: incomplete constraints, leaving VGEN1 on
regulator_init_complete: incomplete constraints, leaving VCAM on
regulator_init_complete: incomplete constraints, leaving VAUDIO on
regulator_init_complete: incomplete constraints, leaving VUSB2 on
regulator_init_complete: incomplete constraints, leaving VSD on
regulator_init_complete: incomplete constraints, leaving VDIG on
regulator_init_complete: incomplete constraints, leaving VPLL on
regulator_init_complete: incomplete constraints, leaving VIOHI on
regulator_init_complete: incomplete constraints, leaving SWBST on

So there's definitely more stuff happening; didn't check what it fixes exactly.

This bug was fixed in the package linux-fsl-imx51 - 2.6.31-105.14

---------------
linux-fsl-imx51 (2.6.31-105.14) karmic; urgency=low

  [ Andy Whitcroft ]

  * rebase to Ubuntu-2.6.31-14.46
  * [Config] update configs since rebase to Ubuntu-2.6.31-14.46
  * lirc update dropped module lirc_mceusb2

  [ Upstream Kernel Changes ]

  * mxc spi: fix spi driver for 2.6.31
    - LP: #427289, #446140

  [ Ubuntu: 2.6.31-14.46 ]

  * reinstate armel.mk with no flavours
    - LP: #449637
  * [Upstream] elevator: fix fastfail checks to allow merge of readahead
    requests
    - LP: #444915
  * [Upstream] block: silently error unsupported empty barriers too
    - LP: #420423
  * SAUCE: AppArmor: Fix mediation of "deleted" paths
    - LP: #415632
  * [Config] CONFIG_X86_MCE
    https://lists.ubuntu.com/archives/kernel-team/2009-October/007584.html
  * Revert "appletalk: Fix skb leak when ipddp interface is not loaded,
    CVE-2009-2903" - Use patch from 2.6.31.4 which is slightly different.
  * x86: fix csum_ipv6_magic asm memory clobber
  * tty: Avoid dropping ldisc_mutex over hangup tty re-initialization
  * x86: Don't leak 64-bit kernel register values to 32-bit processes
  * tracing: correct module boundaries for ftrace_release
  * ftrace: check for failure for all conversions
  * futex: fix requeue_pi key imbalance
  * futex: Move exit_pi_state() call to release_mm()
  * futex: Nullify robust lists after cleanup
  * futex: Fix locking imbalance
  * NOHZ: update idle state also when NOHZ is inactive
  * ima: ecryptfs fix imbalance message
  * libata: fix incorrect link online check during probe
  * sound: via82xx: move DXS volume controls to PCM interface
  * ASoC: WM8350 capture PGA mutes are inverted
  * KVM: Prevent overflow in KVM_GET_SUPPORTED_CPUID
  * KVM: VMX: flush TLB with INVEPT on cpu migration
  * KVM: fix LAPIC timer period overflow
  * KVM: SVM: Fix tsc offset adjustment when running nested
  * KVM: SVM: Handle tsc in svm_get_msr/svm_set_msr correctly
  * net: Fix wrong sizeof
  * mm: add_to_swap_cache() must not sleep
  * sis5513: fix PIO setup for ATAPI devices
  * PIT fixes to unbreak suspend/resume (bug #14222)
  * IMA: open new file for read
  * ACPI: Clarify resource conflict message
  * ACPI: fix Compaq Evo N800c (Pentium 4m) boot hang regression
  * net: restore tx timestamping for accelerated vlans
  * net: unix: fix sending fds in multiple buffers
  * tun: Return -EINVAL if neither IFF_TUN nor IFF_TAP is set.
  * tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()
  * net: Fix sock_wfree() race
  * smsc95xx: fix transmission where ZLP is expected
  * sky2: Set SKY2_HW_RAM_BUFFER in sky2_init
  * appletalk: Fix skb leak when ipddp interface is not loaded
  * ax25: Fix possible oops in ax25_make_new
  * ax25: Fix SIOCAX25GETINFO ioctl
  * sit: fix off-by-one in ipip6_tunnel_get_prl
  * Linux 2.6.31.4
  * drm/i915: Fix FDI M/N setting according with correct color depth
    - LP: #416792

  [ Ubuntu: 2.6.31-13.45 ]

  * [Config] Add sd_mod to scsi-modules udeb for powerpc
  * SAUCE: Update to LIRC 0.8.6
    - LP: #432678
  * [Config] CONFIG_X86_PAT=y
    https://lists.ubuntu.com/archives/kernel-team/2009-October/007477.html...