skiboot v6.1 was released on Wednesday July 11th 2018. It is the first release of skiboot 6.1, which is the new stable release of skiboot following the 6.0 release, first released May 11th 2018.

Skiboot 6.1 is the basis for op-build v2.1 and contains all bug fixes as of skiboot-6.0.5, and skiboot-5.4.9 (the currently maintained stable releases). We expect further stable releases in the 6.0.x and 5.4.x series, while we do not expect to do any stable releases of 6.1.x.

This final 6.1 release follows a single release candidate release, as this cycle we have been rather quiet, with mainly cleanup and bug fix patches going in.

For how the skiboot stable releases work, see Skiboot stable tree rules and releases for details.

Over skiboot-6.0, we have the following changes:

General changes and bug fixes

Since skiboot-6.1-rc1:

  • slw: Fix trivial typo in debug message

  • vpd: Add vendor property to processor node

    Processor FRU vpd doesn’t contain vendor detail. We have to parse module VPD to get vendor detail.

  • vpd: Sanitize VPD data

    On OpenPower system, VPD keyword size tells us the maximum size of the data. But they fill trailing end with space (0x20) instead of NULL. Also spec doesn’t stop user to have space (0x20) within actual data.

    This patch discards trailing spaces before populating device tree.

  • core: always flush console before stopping

    This catches a few cases (e.g., fast reboot failure messages) that don’t always make it to the console before the machine is rebooted.

  • core/cpu: parallelise global CPU register setting jobs

    On a 176 thread system, before:

    [  122.319923233,5] OPAL: Switch to big-endian OS
    [  126.317897467,5] OPAL: Switch to little-endian OS


    [  212.439299889,5] OPAL: Switch to big-endian OS
    [  212.469323643,5] OPAL: Switch to little-endian OS
  • init, occ: Initialise OCC earlier on BMC systems

    We need to use the OCC to obtain presence data for the SXM2 slots on Witherspoon systems. This is needed to determine device type for NVLink GPUs and OpenCAPI devices which can be plugged into the same slot. Support for this will be implemented in a future patch.

    Currently, OCC initialisation is done just before handing over to Linux, which is well after NPU probe. On FSP systems, OCC boot starts very late, so we wait until the last possible moment to initialise the skiboot side in order to give it the maximum time to boot. On BMC systems, OCC boot starts earlier, so there aren’t any issues in moving it earlier in the skiboot init sequence.

    When running on a BMC machine, call occ_pstates_init() as early as possible in the init sequence. On FSP machines, continue to call it from its current location.

Since skiboot-6.0:

  • GCC8 build fixes

  • Add prepare_hbrt_update to hbrt interfaces

    Add placeholder support for prepare_hbrt_update call into hostboot runtime (opal-prd) code. This interface is only called as part of a concurrent code update on a FSP based system.

  • cpu: Clear PCR SPR in opal_reinit_cpus()

    Currently if Linux boots with a non-zero PCR, things can go bad where some early userspace programs can take illegal instructions. This is being fixed in Linux, but in the mean time, we should cleanup in skiboot also.

  • pci: Fix PCI_DEVICE_ID()

    The vendor ID is 16 bits not 8. This error leaves the top of the vendor ID in the bottom bits of the device ID, which resulted in e.g. a failure to run the PCI quirk for the AST VGA device.

  • Quieten console output on boot

    We print out a whole bunch of things on boot, most of which aren’t interesting, so we should not print them instead.

    Printing things like what CPUs we found and what PCI devices we found are useful, so continue to do that. But we don’t need to splat out a bunch of things that are always going to be true.

  • core/console: fix deadlock when printing with console lock held

    Some debugging options will print while the console lock is held, which is why the console lock is taken as a recursive lock. However console_write calls __flush_console, which will drop and re-take the lock non-recursively in some cases.

    Just set con_need_flush and return from __flush_console if we are holding the console lock already.

    This stack usage message (taken with this patch applied) could lead to a deadlock without this:

    CPU 0000 lowest stack mark 11768 bytes left pc=300cb808 token=0
    CPU 0000 Backtrace:
    S: 0000000031c03370 R: 00000000300cb808   .list_check_node+0x1c
    S: 0000000031c03410 R: 00000000300cb910   .list_check+0x38
    S: 0000000031c034b0 R: 00000000300190ac   .try_lock_caller+0xb8
    S: 0000000031c03540 R: 00000000300192e0   .lock_caller+0x80
    S: 0000000031c03600 R: 0000000030012c70   .__flush_console+0x134
    S: 0000000031c036d0 R: 00000000300130cc   .console_write+0x68
    S: 0000000031c03780 R: 00000000300347bc   .vprlog+0xc8
    S: 0000000031c03970 R: 0000000030034844   ._prlog+0x50
    S: 0000000031c03a00 R: 00000000300364a4   .log_simple_error+0x74
    S: 0000000031c03b90 R: 000000003004ab48   .occ_pstates_init+0x184
    S: 0000000031c03d50 R: 000000003001480c   .load_and_boot_kernel+0x38c
    S: 0000000031c03e30 R: 000000003001571c   .main_cpu_entry+0x62c
    S: 0000000031c03f00 R: 0000000030002700   boot_entry+0x1c0
  • opal-prd: Do not error out on first failure for soft/hard offline.

    The memory errors (CEs and UEs) that are detected as part of background memory scrubbing are reported by PRD asynchronously to opal-prd along with affected memory ranges. hservice_memory_error() converts these ranges into page granularity before hooking up them to soft/hard offline-ing infrastructure.

    But the current implementation of hservice_memory_error() does not hookup all the pages to soft/hard offline-ing if any of the page offline action fails. e.g hard offline can fail for:

    • Pages that are not part of buddy managed pool.

    • Pages that are reserved by kernel using memblock_reserved()

    • Pages that are in use by kernel.

    But for the pages that are in use by user space application, the hard offline marks the page as hwpoison, sends SIGBUS signal to kill the affected application as recovery action and returns success.

    Hence, It is possible that some of the pages in that memory range are in use by application or free. By stopping on first error we loose the opportunity to hwpoison the subsequent pages which may be free or in use by application. This patch fixes this issue.

  • libflash/blocklevel_write: Fix missing error handling

    Caught by scan-build, we seem to trap the errors in rc, but not take any recovery action during blocklevel_write.


  • p8-i2c: fix wrong request status when a reset is needed

    If the bus is found in error state when starting a new request, the engine is reset and we enter recovery. However, once complete, the reset operation shows a status of complete in the status register. So any badly-timed called to check_status() will think the current top request is complete, even though it hasn’t run yet.

    So don’t update any request status while we are in recovery, as nothing useful for the request is supposed to happen in that state.

  • p8-i2c: Remove force reset

    Force reset was added as an attempt to work around some issues with TPM devices locking up their I2C bus. In that particular case the problem was that the device would hold the SCL line down permanently due to a device firmware bug. The force reset doesn’t actually do anything to alleviate the situation here, it just happens to reset the internal master state enough to make the I2C driver appear to work until something tries to access the bus again.

    On P9 systems with secure boot enabled there is the added problem of the “diagostic mode” not being supported on I2C masters A,B,C and D. Diagnostic mode allows the SCL and SDA lines to be driven directly by software. Without this force reset is impossible to implement.

    This patch removes the force reset functionality entirely since:

    1. it doesn’t do what it’s supposed to, and

    2. it’s butt ugly code

    Additionally, turn p8_i2c_reset_engine() into p8_i2c_reset_port(). There’s no need to reset every port on a master in response to an error that occurred on a specific port.

  • libstb/i2c-driver: Bump max timeout

    We have observed some TPMs clock streching the I2C bus for signifigant amounts of time when processing commands. The same TPMs also have errata that can result in permernantly locking up a bus in response to an I2C transaction they don’t understand. Using an excessively long timeout to prevent this in the field.

  • hdata: Add TPM timeout workaround

    Set the default timeout for any bus containing a TPM to one second. This is needed to work around a bug in the firmware of certain TPMs that will clock strech the I2C port the for up to a second. Additionally, when the TPM is clock streching it responds to a STOP condition on the bus by bricking itself. Clearing this error requires a hard power cycle of the system since the TPM is powered by standby power.

  • p8-i2c: Allow a per-port default timeout

    Add support for setting a default timeout for the I2C port to the device-tree. This is consumed by skiboot.

IPMI Watchdog

  • ipmi-watchdog: Support handling re-initialization

    Watchdog resets can return an error code from the BMC indicating that the BMC watchdog was not initialized. Currently we abort skiboot due to a missing error handler. This patch implements handling re-initialization for the watchdog, automatically saving the last watchdog set values and re-issuing them if needed.

  • ipmi-watchdog: The stop action should disable reset

    Otherwise it is possible for the reset timer to elapse and trigger the watchdog to wake back up. This doesn’t affect the behavior of the system since we are providing a NONE action to the BMC. However we would like to avoid the action from taking place if possible.

  • ipmi-watchdog: Add a flag to determine if we are still ticking

    This makes it easier for future changes to ensure that the watchdog stops ticking and doesn’t requeue itself for execution in the background. This way it is safe for resets to be performed after the ticks are assumed to be stopped and it won’t start the timer again.

  • ipmi-watchdog: (prepare for) not disabling at shutdown

    The op-build linux kernel has been configured to support the ipmi watchdog. This driver will always handle the watchdog by either leaving it enabled if configured, or by disabling it during module load if no configuration is provided. This increases the coverage of the watchdog during the boot process. The watchdog should no longer be disabled at any point during skiboot execution.

    We’re not enabling this by default yet as people can (and do, at least in development) mix and match old BOOTKERNEL with new skiboot and we don’t want to break that too obviously.

  • ipmi-watchdog: Don’t reset the watchdog twice

    There is no clarification for why this change was needed, but presumably this is due to a buggy BMC implementation where the Watchdog Set command was processed concurrently or after the initial Watchdog Reset. This inversion would cause the watchdog to stop since the DONT_STOP bit was not set. Since we are now using the DONT_STOP bit during initialization, the watchdog should not be stopped even if an inversion occurs.

  • ipmi-watchdog: Make it possible to set DONT_STOP

    The IPMI standard supports setting a DONT_STOP bit during an Watchdog Set operation. Most of the time we don’t want to stop the Watchdog when updating the settings so we should be using this bit. This patch makes it possible for callers of set_wdt to prevent the watchdog from being stopped. This only changes the behavior of the watchdog during the initial settings update when initializing skiboot. The watchdog is no longer disabled and then immediately re-enabled.


    The IPMI specification denotes that action 0x1 is Host Reset and 0x3 is Host Power Cycle. Use the correct name for Reset in our watchdog code.

POWER8 platforms

  • astbmc: Enable mbox depending on scratch reg

    P8 boxes can opt in for mbox pnor support if they set the scratch register bit to indicate it is supported.

Simulator platforms

Since skiboot-6.1-rc1:

  • pmem: volatile bindings for the poorly enabled

    PMEM_DISK bindings were added, but they rely on a rather recent mmap feature. This patch steals from those bindings to add volatile bindings. I’ve used these bindings with PMEM_VOLATILE to launch an instance with the publicly available systemsim-p9. The bindings are volatile and one should not expect any data to be saved/retrieved.

Since skiboot-6.0:

  • plat/qemu: add PNOR support

    To access the PNOR, OPAL/skiboot drives the BMC SPI controller using the iLPC2AHB device of the BMC SuperIO controller and accesses the flash contents using the LPC FW address space on which the PNOR is remapped.

    The QEMU PowerNV machine now integrates such models (SuperIO controller, iLPC2AHB device) and also a pseudo Aspeed SoC AHB memory space populated with the SPI controller registers (same model as for ARM). The AHB window giving access to the contents of the BMC SPI controller flash modules is mapped on the LPC FW address space.

    The change should be compatible for machine without PNOR support.

  • external/mambo: Add support for readline if it exists

    Add support for tclreadline package if it is present. This patch loads the package and uses it when the simulation stops for any reason.

FSP based platforms

  • Disable fast reboot on FSP IPL side change

    If FSP changes next IPL side, then disable fast reboot.

    sample output:

    [  620.196442259,5] FSP: Got sysparam update, param ID 0xf0000007
    [  620.196444501,5] CUPD: FW IPL side changed. Disable fast reboot
    [  620.196445389,5] CUPD: Next IPL side : perm
  • fsp/console: Always establish OPAL console API backend

    Currently we only call set_opal_console() to establish the backend used by the OPAL console API if we find at least one FSP serial port in HDAT.

    On systems where there is none (IPMI only), we fail to set it, causing the console code to try to use the dummy console causing an assertion failure during boot due to clashing on the device-tree node names.

    So always set it if an FSP is present

AST BMC based platforms

  • AMI BMC: use 0x3a as OEM command

    The 0x3a OEM command is for IBM commands, while 0x32 was for AMI ones. Sometime in the P8 timeframe, AMI BMCs were changed to listen for our commands on either 0x32 or 0x3a. Since 0x3a is the direction forward, we’ll use that, as P9 machines with AMI BMCs probably also want these to work, and let’s not bet that 0x32 will continue to be okay.

  • astbmc: Set romulus BMC type to OpenBMC

  • platform/astbmc: Do not delete compatible property

    P9 onwards OPAL is building device tree for BMC based system using HDAT. We are populating bmc/compatible node with bmc version. Hence do not delete this property.


  • external/xscom-utils: Add python library for xscom access

    Patch adds a simple python library module for xscom access. It directly manipulate the ‘/access’ file for scom read and write from debugfs ‘scom’ directory.

    Example on how to generate a getscom using this module:

    from adu_scoms import *
    getscom = GetSCom()

    Sample output for above

    # ./ -l
    Chip ID  | Rev   | Chip type
    00000008 | DD2.0 | P9 (Nimbus) processor
    00000000 | DD2.0 | P9 (Nimbus) processor
  • ffspart: Don’t require user to create blank partitions manually

    Add ‘–allow-empty’ which allows the filename for a given partition to be blank. If set ffspart will set that part of the PNOR file ‘blank’ and set ECC bits if required. Without this option behaviour is unchanged and ffspart will return an error if it can not find the partition file.

  • pflash: Use correct prefix when installing

    pflash uses lowercase prefix when running make install in it’s direcetory, but uppercase PREFIX when running it in shared. Use lowercase everywhere.

    With this the OpenBMC bitbake recipie can drop an out of tree patch it’s been carrying for years.


Since skiboot-6.1-rc1:

  • occ: sensors: Fix the size of the phandle array ‘sensors’ in DT

    Fixes: 99505c03f493 (present in v5.10-rc4)

  • phb4: Delay training till after PERST is deasserted

    This helps some cards train on the second PERST (ie fast-reboot). The reason is not clear why but it helps, so YOLO!

Since skiboot-6.0:

  • occ-sensor: Avoid using uninitialised struct cpu_thread

    When adding the sensors in occ_sensors_init, if the type is not OCC_SENSOR_LOC_CORE, then the loop to find ‘c’ will not be executed. Then c->pir is used for both of the the add_sensor_node calls below.

    This provides a default value of 0 instead.

  • NX: Add NX coprocessor init opal call

    The read offset (4:11) in Receive FIFO control register is incremented by FIFO size whenever CRB read by NX. But the index in RxFIFO has to match with the corresponding entry in FIFO maintained by VAS in kernel. VAS entry is reset to 0 when opening the receive window during driver initialization. So when NX842 is reloaded or in kexec boot, possibility of mismatch between RxFIFO control register and VAS entries in kernel. It could cause CRB failure / timeout from NX.

    This patch adds nx_coproc_init opal call for kernel to initialize readOffset (4:11) and Queued (15:23) in RxFIFO control register.

  • SLW: Remove stop1_lite and stop2_lite

    stop1_lite has been removed since it adds no additional benefit over stop0_lite. stop2_lite has been removed since currently it adds minimal benefit over stop2. However, the benefit is eclipsed by the time required to ungate the clocks

    Moreover, Lite states don’t give up the SMT resources, can potentially have a performance impact on sibling threads.

    Since current OSs (Linux) aren’t smart enough to make good decisions with these stop states, we’re (temporarly) removing them from what we expose to the OS, the idea being to bring them back in a new DT representation so that only an OS that knows what to do will do things with them.

  • cpu: Use STOP1 on POWER9 for idle/sleep inside OPAL

    The current code requests STOP3, which means it gets STOP2 in practice.

    STOP2 has proven to occasionally be unreliable depending on FW version and chip revision, it also requires a functional CME, so instead, let’s use STOP1. The difference is rather minimum for something that is only used a few seconds during boot.

NPU2 (NVLink2 and OpenCAPI)

Since skiboot-6.1-rc1:

  • capi: Select the correct IODA table entry for the mbt cache.

    With the current code, the capi mmio window is not correctly configured in the IODA table entry. The first entry (generally the non-prefetchable BAR) is overwrriten. This patch sets the capi window bar at the right place.

  • npu2/hw-procedures: Fence bricks via NTL instead of MISC

    There are a couple of places we can set/unset fence for a brick:

    1. MISC register: NPU2_MISC_FENCE_STATE

    2. NTL register for the brick: NPU2_NTL_MISC_CFG1(ndev)

    Recent testing of ATS in combination with GPU reset has exposed a side effect of using (1); if fence is set for all six bricks, it triggers a sticky nmmu latch which prevents the NPU from getting ATR responses. This manifests as a hang in the tests.

    We have npu2_dev_fence_brick() which uses (1), and only two calls to it. Replace the call which sets fence with a write to (2). Remove the corresponding unset call entirely. It’s unneeded because the procedures already do a progression from full fence to half to idle using (2).

  • phb4/capp: Calculate STQ/DMA read engines based on link-width for PEC

    Presently in CAPI mode the number of STQ/DMA-read engines allocated on PEC2 for CAPP is fixed to 6 and 0-30 respectively irrespective of the PCI link width. These values are only suitable for x8 cards and quickly run out if a x16 card is plugged to a PEC2 attached slot. This usually manifests as CAPP reporting TLBI timeout due to these messages getting stalled due to insufficient STQs.

    To fix this we update enable_capi_mode() to check if PEC2 chiplet is in x16 mode and if yes then we allocate 4/0-47 STQ/DMA-read engines for the CAPP traffic.

    Fixes: 37ea3cfdc852 (present in v5.7-rc1)

  • npu2: Use same compatible string for NVLink and OpenCAPI link nodes in device tree

    Currently, we distinguish between NPU links for NVLink devices and OpenCAPI devices through the use of two different compatible strings - ibm,npu-link and ibm,npu-link-opencapi.

    As we move towards supporting configurations with both NVLink and OpenCAPI devices behind a single NPU, we need to detect the device type as part of presence detection, which can’t happen until well after the point where the HDAT or platform code has created the NPU device tree nodes. Changing a node’s compatible string after it’s been created is a bit ugly, so instead we should move the device type to a new property which we can add to the node later on.

    Get rid of the ibm,npu-link-opencapi compatible string, add a new ibm,npu-link-type property, and a helper function to check the link type. Add an “unknown” device type in preparation for later patches to detect device type dynamically.

    These device tree bindings are entirely internal to skiboot and are not consumed directly by Linux, so this shouldn’t break anything (other than internal BML lab environments).

  • occ: Add support for GPU presence detection

    On the Witherspoon platform, we need to distinguish between NVLink GPUs and OpenCAPI accelerators. In order to do this, we first need to find out whether the SXM2 socket is populated.

    On Witherspoon, the SXM2 socket’s presence detection pin is only visible via I2C from the APSS, and thus can only be exposed to the host via the OCC. The OCC, per OCC Firmware Interface Specification for POWER9 version 0.22, now exposes this to skiboot through a field in the dynamic data shared memory.

    Add the necessary dynamic data changes required to read the version and GPU presence fields. Add a function, occ_get_gpu_presence(), that can be used to check GPU presence.

    If the OCC isn’t reporting presence (old OCC firmware, or some other reason), we default to assuming there is a device present and wait until link training to fail.

    This will be used in later patches to fix up the NPU2 probe path for OpenCAPI support on Witherspoon.

  • hw/npu2, core/hmi: Use NPU instead of NPU2 as log message prefix

    The NPU2{DBG,INF,ERR} macros use “NPU%d” as a prefix to identify messages relating to a particular NPU.

    It’s slightly confusing to have per-NPU messages prefixed with “NPU0” or “NPU1” and NPU-generic messages prefixed with “NPU2”. On some future system we could potentially have a NPU #2 in which case it’d be really confusing.

    Use NPU rather than NPU2 for NPU-generic log messages. There’s no risk of confusion with the original npu.c code since that’s only for P8.

Since skiboot-6.0:

  • npu2: Reset NVLinks on hot reset

    This effectively fences GPU RAM on GPU reset so the host system does not have to crash every time we stop a KVM guest with a GPU passed through.

  • npu2-opencapi: reduce number of retries to train the link

    We’ve been reliably training the opencapi link on the first attempt for quite a while. Furthermore, if it doesn’t train on the first attempt, retries haven’t been that useful. So let’s reduce the number of attempts we do to train the link.

    2 retries = 3 attempts to train.

    Each (failed) training sequence costs about 3 seconds.

  • opal/hmi: Display correct chip id while printing NPU FIRs.

    HMIs for NPU xstops are broadcasted to all chips. All cores on all the chips receive HMI. HMI handler correctly identifies and extracts the NPU FIR details from affected chip, but while printing FIR data it prints chip id and location code details of this_cpu()->chip_id which may not be correct. This patch fixes this issue.

  • npu2-opencapi: Fix link state to report link down

    The PHB callback ‘get_link_state’ is always reporting the link width, irrespective of the link status and even when the link is down. It is causing too much work (and failures) when the PHB is probed during pci init. The fix is to look at the link status first and report the link as down when appropriate.

  • npu2-opencapi: Cleanup traces printed during link training

    Now that links may train in parallel, traces shown during training can be all mixed up. So add a prefix to all the traces to clearly identify the chip and link the trace refers to:

    OCAPI[<chip id>:<link id>]: this is a very useful message

    The lower-level hardware procedures (npu2-hw-procedures.c) also print traces which would need work. But that code is being reworked to be better integrated with opencapi and nvidia, so leave it alone for now.

  • npu2-opencapi: Train links on fundamental reset

    Reorder our link training steps so that they are executed on fundamental reset instead of during the initial setup. Skiboot always call a fundamental reset on all the PHBs during pci init.

    It is done through a state machine, similarly to what is done for ‘real’ PHBs.

    This is the first step for a longer term goal to be able to trigger an adapter reset from linux. We’ll need the reset callbacks of the PHB to be defined. We have to handle the various delays differently, since a linux thread shouldn’t stay stuck waiting in opal for too long.

  • npu2-opencapi: Rework adapter reset

    Rework a bit the code to reset the opencapi adapter:

    • make clearer which i2c pin is resetting which device

    • break the reset operation in smaller chunks. This is really to prepare for a future patch.

    No functional changes.

  • npu2-opencapi: Use presence detection

    Presence detection is not part of the opencapi specification. So each platform may choose to implement it the way it wants.

    All current platforms implement it through an i2c device where we can query a pin to know if a device is connected or not. ZZ and Zaius have a similar design and even use the same i2c information and pin numbers. However, presence detection on older ZZ planar (older than v4) doesn’t work, so we don’t activate it for now, until our lab systems are upgraded and it’s better tested.

    Presence detection on witherspoon is still being worked on. It’s shaping up to be quite different, so we may have to revisit the topic in a later patch.

Testing and CI

Since skiboot-6.1-rc1:

  • test/qemu: start building qemu again, and use our built qemu for tests

    We need to use QEMU_BIN rather than QEMU as the makefiles define QEMU already.

  • opal-ci: qemu: Use the powernv-3.0 branch

    This is based off the current development version of Qemu, and importantly it contains the patch that allows skiboot and Linux to clear the PCR that we require to boot.