skiboot-5.4.0 was released on Friday November 11th 2016. It is the new stable skiboot release, taking over from the 5.3.x series (first released August 2nd, 2016). It comes after four release candidates, which have helped to shake out a few issues.

skiboot-5.4.0 contains all bug fixes as of skiboot-5.3.7 and skiboot-5.1.18 (the currently maintained stable releases).

Skiboot 5.4.x becomes the new stable release. For how the skiboot stable releases work, see Skiboot stable tree rules and releases for details.

Over skiboot-5.4.0-rc4, we have a few changes:

  • libstb: bump up the byte timeout for tpm i2c requests

    This bumps up the byte timeout for tpm i2c requests from 10ms to 30ms. Some p8dtu systems are getting i2c request timeout.

  • external/pflash: Perform the correct cleanup when -F is used to operate on a file.

  • Add SuperMicro p8dtu1u and p8dtu2u platforms

  • Revert “core/ipmi: Set interrupt-parent property”. This reverts commit d997e482705d9fdff8e25fcbe07fb56008f96ae1 (introduced in 5.4.0-rc1)

    A problem was found with pre 4.2 linux kernels where a spurious WARNING would be emitted. This change doesn’t matter enough to scare users so we can just revert it.

    Warning was:
    [    0.947741] irq: irq-62==>hwirq-0x3e mapping failed: -22
    [    0.947793] ------------[ cut here ]------------
    [    0.947838] WARNING: at kernel/irq/irqdomain.c:485
  • libflash/libffs: Fix possible NULL dereference

Previous Release Candidates

There were four release candidates for skiboot 5.4.0:

Changes since skiboot 5.3

Over skiboot-5.3, we have the following changes:

New Features

  • Add SuperMicro p8dtu1u and p8dtu2u platforms

  • Initial Trusted Boot support (see Secure and Trusted Boot Library (LibSTB) Documentation). There are several limitations with this initial release:

    • Only Nuvoton TPM 2.0 is supported
    • Requires hardware rework on late revision Habanero or Firestone boards in order to install TPM.
  • Support ibm,skiboot NVRAM partition with skiboot configuration options.

    • These should generally only be used if you either completely know what you are doing or need to work around a skiboot bug. They are not intended for end users and are explicitly NOT ABI.
    • Add support for supplying the kernel boot arguments from the bootargs configuration string in the ibm,skiboot NVRAM partition.
    • Enabling the experimental fast reset feature is done via this method.
  • Add support for nap mode on P8 while in skiboot

    • While nap has been exposed to the Operating System since day 1, we have not utilized low power states when in skiboot itself, leading to higher power consumption during boot. We only enable the functionality after the 0x100 vector has been patched, and we disable it before transferring control to Linux.
  • libflash: add 128MB MX66L1G45G part

  • Pointer validation of OPAL API call arguments.

    • If the kernel called an OPAL API with vmalloc’d address or any other address range in real mode, we would hit a problem with aliasing. Since the top 4 bits are ignored in real mode, pointers from 0xc.. and 0xd.. (and other ranges) could collide and lead to hard to solve bugs. This patch adds the infrastructure for pointer validation and a simple test case for testing the API
    • The checks validate pointers sent in using opal_addr_valid()
  • Fast reboot for P8

    This makes reboot take an awful lot less time, somewhere between four and ten times faster than a full IPL. It is currently experimental and not enabled by default. You can enable the experimental support via nvram option:

    # nvram -p ibm,skiboot --update-config experimental-fast-reset=feeling-lucky

    WARNING: While we think we’ve managed to work out or around most of the kinks with fast-reset, we are not enabling it by default in 5.4.

    Notably, fast reset will not happen in the following scenarios:

    • platform error

      Most of the time, if we’re rebooting due to a platform error, we should trigger a checkstop. However, if we haven’t been told what we should do to trigger a checkstop (e.g. on an FSP machine), then we should still fail to fast-reboot.

      So, fast-reboot is disabled in the OPAL_CEC_REBOOT2 code path for the OPAL_REBOOT_PLATFORM_ERROR reboot type.

    • FSP code update

    • Unrecoverable HMI

    • A PHB is in CAPI mode

      If a PHB is in CAPI mode, we cannot safely fast reboot - the PHB will be fenced during the reboot resulting in major problems when we load the new kernel.

      In order to handle this safely, we need to disable CAPI mode before resetting PHBs during the fast reboot. However, we don’t currently support this.

      In the meantime, when fast rebooting, check if there are any PHBs with a CAPP attached, and if so, abort the fast reboot and revert to a normal reboot instead.


There have been a number of documentation fixes this release. Most prominent is the switch to Sphinx (from the Python project) and ReStructured Text (RST) as the documentation format. RST and Sphinx enable both production of pretty documentation in HTML and PDF formats while remaining readable in their raw form to those with no knowledge of RST.

You can build a HTML site by doing the following:

cd doc/
make html

As always, documentation patches are very, very welcome as we attempt to document the OPAL API, the device tree bindings and important parts of OPAL internals.

We would like the Device Tree documentation to follow the style that can be included in the Device Tree Specification.


  • Make console-log time more readable: seconds rather than timebase Log format is now [SECONDS.(tb%512000000),LEVEL]

  • Flash (PNOR) code improvements

    • flash: Make size 64 bit safe This makes the size of flash 64 bit safe so that we can have flash devices greater than 4GB. This is especially useful for mambo disks passed through to Linux.
    • core/flash.c: load actual partition size We are downloading 0x20000 bytes from PNOR for CAPP, but currently the CAPP lid is only 40K.
    • flash: Rework error paths and messages for multiple flash controllers Now that we have mambo bogusdisk flash, we can have many flash chips. This is resulting in some confusing output messages.
  • core/init: Fix “failure of getting node in the free list” warning on boot.

  • slw: improve error message for SLW timer stuck

  • Centaur / XSCOM error handling

    • print message on disabling xscoms to centaur due to many errors
    • Mark centaur offline after 10 consecutive access errors
  • XSCOM improvements

    • xscom: Map all HMER status codes to OPAL errors
    • xscom: Initialize the data to a known value in xscom_read In case of error, don’t leave the data random. It helps debugging when the user fails to check the error code. This happens due to a bug in the PRD wrapper app.
    • chip: Add a quirk for when core direct control XSCOMs are missing
  • p8-i2c: Don’t crash if a centaur errored out

  • cpu: Make endian switch message more informative

  • cpu: Display number of started CPUs during boot

  • core/init: ensure that HRMOR is zero at boot

  • asm: Fix backtrace for unexpected exception

  • cpu: Remove pollers calling heuristics from cpu_wait_job This will be handled by time_wait_ms(). Also remove a useless smt_medium(). Note that this introduce a difference in behaviour: time_wait will only call the pollers on the boot CPU while cpu_wait_job() could call them on any. However, I can’t think of a case where this is a problem.

  • cpu: Remove global job queue Instead, target a specific CPU for a global job at queuing time. This will allow us to wake up the target using an interrupt when implementing nap mode. The algorithm used is to look for idle primary threads first, then idle secondaries, and finally the less loaded thread. If nothing can be found, we fallback to a synchronous call.

  • lpc: Log LPC SYNC errors as unrecoverable ones for manufacturing

  • lpc: Optimize SerIRQ dispatch based on which PSI IRQ fired

  • interrupts: Add new source ->attributes() callback

    This allows a given source to provide per-interrupt attributes such as whether it targets OPAL or Linux and it’s estimated frequency.

    The former allows to get rid of the double set of ops used to decide which interrupts go where on some modules like the PHBs and the latter will be eventually used to implement smart caching of the source lookups.

  • opal/hmi: Fix a TOD HMI failure during a race condition.

  • platform: Add BT to Generic platform


  • Support ibm,skiboot partition for skiboot specific configuration options
  • flash: Size NVRAM based on ECC for OpenPOWER platforms
    If NVRAM has ECC (as per the ffs header) then the actual size of the partition is less than reported by the ffs header in the PNOR then the actual size of the partition is less than reported by the ffs header.


  • Generic fixes

    • Claim surprise hotplug capability

    • Reserve PCI buses for RC’s slot

    • Update PCI topology after power change

    • Return slot cached power state

    • Cache power state on slot without power control

    • Avoid hot resets at boot time

    • Fix initial PCIe slot power state

    • Print CRS retry times It’s useful to know the CRS retry times before the PCI device is detected successfully. In PCI hot add case, it usually indicates time consumed for the adapter’s firmware to be partially ready (responsive PCI config space).

    • core/pci: Fix the power-off timeout in pci_slot_power_off() The timeout should be 1000ms instead of 1000 ticks while powering off PCI slot in pci_slot_power_off(). Otherwise, it’s likely to hit timeout powering off the PCI slot as below skiboot logs reveal:

      [5399576870,5] PHB#0005:02:11.0 Timeout powering off slot
    • pci: Check power state before powering off slot. Prevents the erroneous “Error -1 powering off slot” error message.

  • PHB3

    • Override root slot’s prepare_link_change() with PHB’s
    • Disable surprise link down event on PCI slots
    • Disable ECRC on Broadcom adapter behind PMC switch
  • astbmc platforms

    • Support dynamic PCI slot. We might insert a PCIe switch to PHB direct slot and the downstream ports of the PCIe switch supports PCI hotplug.


  • hw/phb3: Update capi initialization sequence
    The capi initialization sequence was revised in a circumvention document when a ‘link down’ error was converted from fatal to Endpoint Recoverable. Other, non-capi, register setup was corrected even before the initial open-source release of skiboot, but a few capi-related registers were not updated then, so this patch fixes it.

Mambo Simulator

  • Helpers for POWER9 Mambo.
  • mambo: Advertise available RADIX page sizes
  • mambo: Add section for kernel command line boot args Users can set kernel command line boot arguments for Mambo in a tcl script.
  • mambo: add exception and qtrace helpers
  • external/mambo: Update skiboot.tcl to add page-sizes nodes to device tree

Simics Simulator

  • chiptod: Enable ChipTOD in SIMICS


  • pflash

    • fix harmless buffer overflow: fl_total_size was uint32_t not uint64_t.

    • Don’t try to write protect when writing to flash file

    • Misc small improvements to code and code style

    • makefile bug fixes

    • external/pflash: Make MTD accesses the default

      Now that BMC and host kernel mtd drivers exist and have matured we should use them by default.

      This is especially important since we seem to be telling everyone to use pflash (pflash world domination plans are continuing on schedule).

    • external/pflash: Catch incompatible combination of flags

    • external/common: arm: Don’t error trying to wrprotect with MTD access

    • libflash/libffs: Use blocklevel_smart_write() when updating partitions

  • external/boot_tests

    • remove lid from the BMC after flashing
    • add the nobooting option -N
    • add arbitrary lid option -F
  • getscom / getsram / putscom: Parse chip-id as hex

    We print the chip-id in hex (without a leading 0x), but we fail to parse that same value correctly in getscom / getsram / putscom

    # getscom -l
    80000000 | DD2.0 | Centaur memory buffer
    # getscom -c 80000000 201140a
    Error -19 reading XSCOM

    Fix this by assuming base 16 when parsing chip-id.


  • opal-prd: Fix error code from scom_read and scom_write
  • opal-prd: Add get_interface_capabilities to host interfaces
  • opal-prd: fix for 64-bit pnor sizes
  • occ/prd/opal-prd: Queue OCC_RESET event message to host in OpenPOWER
    During an OCC reset cycle the system is forced to Psafe pstate. When OCC becomes active, the system has to be restored to its last pstate as requested by host. So host needs to be notified of OCC_RESET event or else system will continue to remian in Psafe state until host requests a new pstate after the OCC reset cycle.

IBM FSP Based Platforms

  • fsp/console: Allocate irq for each hvc console

    Allocate an irq number for each hvc console and set its interrupt-parent property so that Linux can use the opal irqchip instead of the OPAL_EVENT_CONSOLE_INPUT interface.

  • platforms/firenze: Fix clock frequency dt property:

    [ 1.212366090,3] DT: Unexpected property length /xscom@3fc0000000000/i2cm@a0020/clock-frequency
  • HDAT: Fix typo in nest-frequency property

    nest-frquency -> nest-frequency

  • platforms/ibm-fsp: Use power_ctl bit when determining slot reset method

    The power_ctl bit is used to represent if power management is available. If power_ctl is set to true, then the I2C based external power management functionality will be populated on the PCI slot. Otherwise we will try to use the inband PERST as the fundamental reset, as before.

  • FSP/ELOG: Fix elog timeout issue

    Presently we set timeout value as soon as we add elog to queue. If we have multiple elogs to write, it doesn’t consider queue wait time. Instead set timeout value when we are actually sending elog to FSP.

  • FSP/ELOG: elog_enable flag should be false by default

    This issue is one of the corner case, which is related to recent change went upstream and only observed in the petitboot prompt, where we see only one error log instead of getting all error log in /sys/firmware/opal/elog.


Skiboot 5.4 contains only preliminary support for POWER9. It’s suitable only for use in simulators. If working on hardware, use more recent skiboot or development branches. We will not be backporting POWER9 fixes to 5.4.x.

  • mambo: Make POWER9 look like DD2
  • core/cpu.c: Add OPAL call to setup Nest MMU
  • psi: On p9, create an interrupt-map for routing PSI interrupts
  • lpc: Add P9 LPC interrupts support
  • chiptod: Basic P9 support
  • psi: Add P9 support

Testing and Debugging

  • test/qemu: bump qemu version used in CI, adds IPMI support
  • platform/qemu: add BT and IPMI support Enables testing BT and IPMI functionality in the Qemu simulator
  • init: In debug builds, enable debug output to console
  • mem_region: Be a bit smarter about poisoning
    Don’t poison chunks that are already free and poison regions on first allocation. This speeds things up dramatically.
  • libc: Use 8-bytes stores for non-0 memset too
    Memory poisoning hammers this, so let’s be a bit smart about it and avoid falling back to byte stores when the data is not 0
  • fwts: add annotation for manufacturing mode
  • check: Fix bugs in mem region tests
  • Don’t set -fstack-protector-all unconditionally
    We set it already in DEBUG builds and we use -fstack-protector-strong in release builds which provides most of the benefits and is more efficient.
  • Build host programs (and checks) with debug enabled
    This enables memory poisoning in allocations and list checking among other things.
  • Add global DEBUG make flag

Command line arguments to BOOTKERNEL

  • core/init.c: Fix bootargs parsing

    Currently the bootargs are unconditionally deleted, which causes a bug where the bootargs passed in by the device tree are lost.

    This patch deletes bootargs only if it needs to be replaced by the NVRAM entry.

    This patch also removes KERNEL_COMMAND_LINE config option in favour of using the NVRAM or a device tree.

Other changes

  • extract-gcov: build with -m64 if compiler supports it.

    Fixes build break on 32bit ppc64 (e.g. PowerMac G5, where user space is mostly 32bit).

Flash on OpenPOWER platforms

  • flash: rework flash_load_resource to correctly read FFS/STB

    This fixes the previous reverts of loading the CAPP partition with STB headers (which broke CAPP partitions without STB headers).

    The new logic fixes both CAPP partition loading with STB headers and addresses a long standing bug due to differing interpretations of FFS.

    The f_part utility that constructs PNOR files just sets actualSize=totalSize no matter on what the size of the partition is. Prior to this patch, skiboot would always load actualSize, leading to longer than needed IPL.

    The pflash utility updates actualSize, so no developer has really ever noticed this, apart from maybe an inkling that it’s odd that a freshly baked PNOR from op-build takes ever so slightly longer to boot than one that has had individual partitions pflashed in.

    With this patch, we now compute actualSize. For partitions with a STB header, we take the payload size from the STB header. For partitions that don’t have a STB header, we compute the size either by parsing the ELF header or by looking at the subpartition header and computing it.

    We now need to read the entire partition for partitions with subpartitions so that we pass consistent values to be measured as part of Trusted Boot.

    As of this patch, the actualSize field in FFS is not relied on for partition size, we determine it from the content of the partition.

    However, this patch will break loading of partitions that are not ELF and do not contain subpartitions. Luckily, nothing in-tree makes use of that.


Extending the analysis done for the last few releases, we can see our trends in code review across versions:

Release csets Ack Reviews Tested Reported
5.0 329 15 20 1 0
5.1 372 13 38 1 4
5.2-rc1 334 20 34 6 11
5.3-rc1 302 36 53 4 5
5.4-rc1 278 8 19 0 4
5.4.0 361 16 28 1 9

Interesting is the stats of 5.4.0-rc1 versus the final 5.4.0, there’s been a doubling of Acks, an increase in reviewed-by and reported-by. There’s nothing like an impending release to get people to look closer.

Processed 361 csets from 34 developers A total of 20206 lines added, 5843 removed (delta 14363)

Developers with the most changesets:

Developer # %
Stewart Smith 105 (29.1%)
Benjamin Herrenschmidt 50 (13.9%)
Claudio Carvalho 47 (13.0%)
Gavin Shan 24 (6.6%)
Cyril Bur 20 (5.5%)
Oliver O’Halloran 18 (5.0%)
Michael Neuling 12 (3.3%)
Mukesh Ojha 12 (3.3%)
Pridhiviraj Paidipeddi 7 (1.9%)
Vasant Hegde 7 (1.9%)
Russell Currey 7 (1.9%)
Joel Stanley 4 (1.1%)
Alistair Popple 4 (1.1%)
Mahesh Salgaonkar 4 (1.1%)
Nageswara R Sastry 4 (1.1%)
Chris Smart 3 (0.8%)
Sam Mendoza-Jonas 3 (0.8%)
Vipin K Parashar 3 (0.8%)
Balbir Singh 3 (0.8%)
Frederic Barrat 3 (0.8%)
leoluo 2 (0.6%)
Rafael Fonseca 2 (0.6%)
Jack Miller 2 (0.6%)
Patrick Williams 2 (0.6%)
Jeremy Kerr 2 (0.6%)
Suraj Jitindar Singh 2 (0.6%)
Milton Miller 2 (0.6%)
Andrew Donnellan 1 (0.3%)
Shilpasri G Bhat 1 (0.3%)
Frederic Bonnard 1 (0.3%)
Breno Leitao 1 (0.3%)
Anton Blanchard 1 (0.3%)
Nicholas Piggin 1 (0.3%)
Cédric Le Goater 1 (0.3%)

Developers with the most changed lines:

Developer # %
Claudio Carvalho 6947 (32.9%)
Stewart Smith 6667 (31.6%)
Benjamin Herrenschmidt 2586 (12.3%)
Gavin Shan 1185 (5.6%)
Cyril Bur 692 (3.3%)
Mukesh Ojha 565 (2.7%)
Oliver O’Halloran 343 (1.6%)
Russell Currey 343 (1.6%)
leoluo 269 (1.3%)
Pridhiviraj Paidipeddi 236 (1.1%)
Balbir Singh 227 (1.1%)
Michael Neuling 211 (1.0%)
Nageswara R Sastry 132 (0.6%)
Cédric Le Goater 115 (0.5%)
Vipin K Parashar 68 (0.3%)
Alistair Popple 66 (0.3%)
Vasant Hegde 65 (0.3%)
Mahesh Salgaonkar 50 (0.2%)
Shilpasri G Bhat 45 (0.2%)
Suraj Jitindar Singh 41 (0.2%)
Nicholas Piggin 34 (0.2%)
Sam Mendoza-Jonas 33 (0.2%)
Jack Miller 32 (0.2%)
Chris Smart 28 (0.1%)
Jeremy Kerr 23 (0.1%)
Milton Miller 19 (0.1%)
Joel Stanley 13 (0.1%)
Andrew Donnellan 13 (0.1%)
Rafael Fonseca 12 (0.1%)
Patrick Williams 11 (0.1%)
Frederic Barrat 6 (0.0%)
Anton Blanchard 3 (0.0%)
Frederic Bonnard 2 (0.0%)
Breno Leitao 2 (0.0%)

Developers with the most lines removed:

Developer # %
Cyril Bur 206 (3.5%)
Rafael Fonseca 8 (0.1%)

Developers with the most signoffs (total 278):

Developer # %
Stewart Smith 268 (96.4%)
Alistair Popple 4 (1.4%)
Jim Yuan 2 (0.7%)
Cyril Bur 1 (0.4%)
Michael Neuling 1 (0.4%)
Jeremy Kerr 1 (0.4%)
Benjamin Herrenschmidt 1 (0.4%)

Developers with the most reviews (total 28):

Developer # %
Andrew Donnellan 6 (21.4%)
Vasant Hegde 5 (17.9%)
Mukesh Ojha 5 (17.9%)
Joel Stanley 3 (10.7%)
Russell Currey 3 (10.7%)
Cyril Bur 2 (7.1%)
Balbir Singh 2 (7.1%)
Alistair Popple 1 (3.6%)
Vaidyanathan Srinivasan 1 (3.6%)

Developers with the most test credits (total 1):

Developer # %
Pridhiviraj Paidipeddi 1 (100.0%)

Developers who gave the most tested-by credits (total 1):

Developer # %
Gavin Shan 1 (100.0%)

Developers with the most report credits (total 9):

Developer # %
Pridhiviraj Paidipeddi 3 (33.3%)
Gavin Shan 1 (11.1%)
Vasant Hegde 1 (11.1%)
Michael Neuling 1 (11.1%)
Benjamin Herrenschmidt 1 (11.1%)
Andrei Warkenti 1 (11.1%)
Li Meng 1 (11.1%)