skiboot v6.2.2 release notes

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
(cherry picked from commit 5da21e2)
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

doc/release-notes/skiboot-6.2.2.rst

@@ -0,0 +1,227 @@
+.. _skiboot-6.2.2:
+
+==============
+skiboot-6.2.2
+==============
+
+skiboot 6.2.2 was released on Wednesday March 6th, 2019. It replaces
+:ref:`skiboot-6.2.1` as the current stable release in the 6.2.x series.
+
+It is recommended that 6.2.2 be used instead of any previous 6.2.x version
+due to the bug fixes it contains.
+
+Over :ref:`skiboot-6.2.1` we have several bug fixes, including important ones
+for powercap, ipmi-hiomap, astbmc and BMC communication driver.
+
+powercap
+========
+- powercap: occ: Fix the powercapping range allowed for user
+
+  OCC provides two limits for minimum powercap. One being hard powercap
+  minimum which is guaranteed by OCC and the other one is a soft
+  powercap minimum which is lesser than hard-min and may or may not be
+  asserted due to various power-thermal reasons. So to allow the users
+  to access the entire powercap range, this patch exports soft powercap
+  minimum as the "powercap-min" DT property. And it also adds a new
+  DT property called "powercap-hard-min" to export the hard-min powercap
+  limit.
+
+ASTBMC
+=====
+- astbmc: Enable IPMI HIOMAP for AMI platforms
+
+  Required for Habanero, Palmetto and Romulus.
+
+- astbmc: Try IPMI HIOMAP for P8 (again)
+
+  The HIOMAP protocol was developed after the release of P8 in preparation
+  for P9. As a consequence P9 always uses it, but it has rarely been
+  enabled for P8. P8DTU has recently added IPMI HIOMAP support to its BMC
+  firmware, so enable its use in skiboot with P8 machines. Doing so
+  requires some rework to ensure fallback works correctly as in the past
+  the fallback was to mbox, which will only work for P9.
+
+  Tested on Garrison, Palmetto without HIOMAP, Palmetto with HIOMAP, and
+  Witherspoon.
+
+- ast-io: Rework ast_sio_is_enabled() test sequence
+
+  The postcondition of probing with a lock sequence is easier to make
+  correct than with unlock. The original implementation left SuperIO
+  locked after execution which broke an assumption of some callers.
+
+  Tested on Garrison, Palmetto without HIOMAP, Palmetto with HIOMAP and
+  Witherspoon.
+
+P8DTU
+=====
+- p8dtu: Enable HIOMAP support
+
+- p8dtu: Configure BMC graphics
+
+  We can no-longer read the values from the BMC in the way we have in the
+  past. Values were provided by Eric Chen of SMC.
+
+IPMI-HIOMAP
+===========
+- ipmi-hiomap test case enhancements/fixes.
+
+- libflash/ipmi-hiomap: Enforce message size for empty response
+
+  The protocol defines the response to the associated messages as empty
+  except for the command ID and sequence fields. If the BMC is returning
+  extra data consider the message malformed.
+
+- libflash/ipmi-hiomap: Remove unused close handling
+
+  Issuing a HIOMAP_C_CLOSE is not required by the protocol specification,
+  rather a close can be implicit in a subsequent
+  CREATE_{READ,WRITE}_WINDOW request. The implicit close provides an
+  opportunity to reduce LPC traffic and the implementation takes up that
+  optimisation, so remove the case from the IPMI callback handler.
+
+- libflash/ipmi-hiomap: Overhaul event handling
+
+  Reworking the event handling was inspired by a bug report by Vasant
+  where the host would get wedged on multiple flash access attempts in the
+  face of a persistent error state on the BMC-side. The cause of this bug
+  was the early-exit based on ctx->update, which erronously assumed that
+  all events had been completely handled in prior calls to
+  ipmi_hiomap_handle_events(). This is not true if e.g.
+  HIOMAP_E_DAEMON_READY is clear in the prior calls.
+
+  Regardless, there were other correctness and efficiency problems with
+  the handling strategy:
+
+  * Ack-able event state was not restored in the face of errors in the
+    process of re-establishing protocol state
+
+  * It forced needless window restoration with respect to the context in
+    which ipmi_hiomap_handle_events() was called.
+
+  * Tests for HIOMAP_E_DAEMON_READY and HIOMAP_E_FLASH_LOST were redundant
+    with the overhauled error handling introduced in the previous patch
+
+  Fix all of the above issues and add comments to explain the event
+  handling flow.
+
+  Tests for correctness follow later in the series.
+
+- libflash/ipmi-hiomap: Overhaul error handling
+
+  The aim is to improve the robustness with respect to absence of the
+  BMC-side daemon. The current error handling roughly mirrors what was
+  done for the mailbox implementation, but there's room for improvement.
+
+  Errors are split into two classes, those that affect the transport state
+  and those that affect the window validity. From here, we push the
+  transport state error checks right to the bottom of the stack, to ensure
+  the link is known to be in a good state before any message is sent.
+  Window validity tests remain as they were in the hiomap_window_move()
+  and ipmi_hiomap_read() functions. Validity tests are not necessary in
+  the write and erase paths as we will receive an error response from the
+  BMC when performing a dirty or flush on an invalid window.
+
+  Recovery also remains as it was, done on entry to the blocklevel
+  callbacks. If an error state is encountered in the middle of an
+  operation no attempt is made to recover it on the spot, instead the
+  error is returned up the stack and the caller can choose how it wishes
+  to respond.
+
+- libflash/ipmi-hiomap: Fix leak of msg in callback
+
+BMC communication
+=================
+- core/ipmi: Add ipmi sync messages to top of the list
+
+  In ipmi_queue_msg_sync() path OPAL will wait until it gets response from
+  BMC. If we do not get response ontime we may endup in kernel hardlockups.
+  Hence lets add sync messages to top of the queue. This will reduces the
+  chance of hardlockups.
+
+- hw/bt: Introduce separate list for synchronous messages
+
+  BT send logic always sends top of bt message list to BMC. Once BMC reads the
+  message, it clears the interrupt and bt_idle() becomes true.
+
+  bt_add_ipmi_msg_head() adds message to top of the list. If bt message list
+  is not empty then:
+    - if bt_idle() is true then we will endup sending message to BMC before
+      getting response from BMC for inflight message. Looks like on some
+      BMC implementation this results in message timeout.
+    - else we endup starting message timer without actually sending message
+      to BMC.. which is not correct.
+
+  This patch introduces separate list to track synchronous messages.
+  bt_add_ipmi_msg_head() will add messages to tail of this new list. We
+  will always process this queue before processing normal queue.
+
+  Finally this patch introduces new variable (inflight_bt_msg) to track
+  inflight message. This will point to current inflight message.
+
+- hw/bt: Fix message retry handler
+
+  In some corner cases (like BMC reboot), bt_send_and_unlock() starts
+  message timer, but won't send message to BMC as driver is not free to
+  send message. bt_expire_old_msg() function enables H2B interrupt without
+  actually sending message.
+
+  This patch fixes above issue.
+
+- ipmi/power: Fix system reboot issue
+
+  Kernel makes reboot/shudown OPAL call for reboot/shutdown. Once kernel
+  gets response from OPAL it runs opal_poll_events() until firmware
+  handles the request.
+
+  On BMC based system, OPAL makes IPMI call (IPMI_CHASSIS_CONTROL) to
+  initiate system reboot/shutdown. At present OPAL queues IPMI messages
+  and return SUCESS to Host. If BMC is not ready to accept command (like
+  BMC reboot), then these message will fail. We have to manually
+  reboot/shutdown the system using BMC interface.
+
+  This patch adds logic to validate message return value. If message failed,
+  then it will resend the message. At some stage BMC will be ready to accept
+  message and handles IPMI message.
+
+- hw/bt: Add backend interface to disable ipmi message retry option
+
+  During boot OPAL makes IPMI_GET_BT_CAPS call to BMC to get BT interface
+  capabilities which includes IPMI message max resend count, message
+  timeout, etc,. Most of the time OPAL gets response from BMC within
+  specified timeout. In some corner cases (like mboxd daemon reset in BMC,
+  BMC reboot, etc) OPAL may not get response within timeout period. In
+  such scenarios, OPAL resends message until max resend count reaches.
+
+  OPAL uses synchronous IPMI message (ipmi_queue_msg_sync()) for few
+  operations like flash read, write, etc. Thread will wait in OPAL until
+  it gets response from BMC. In some corner cases like BMC reboot, thread
+  may wait in OPAL for long time (more than 20 seconds) and results in
+  kernel hardlockup.
+
+  This patch introduces new interface to disable message resend option. We
+  will disable message resend option for synchrous message. This will
+  greatly reduces kernel hardlock up issues.
+
+  This is short term fix. Long term solution is to convert all synchronous
+  messages to asynhrounous one.
+
+- qemu: bt device isn't always hanging off /
+
+  Just use the normal for_each_compatible instead.
+
+  Otherwise in the qemu model as executed by op-test,
+  we wouldn't go down the astbmc_init() path, thus not having flash.
+
+PHB3
+====
+- hw/phb3/naples: Disable D-states
+
+  Putting "Mellanox Technologies MT27700 Family [ConnectX-4] [15b3:1013]"
+  (more precisely, the second of 2 its PCI functions, no matter in what
+  order) into the D3 state causes EEH with the "PCT timeout" error.
+  This has been noticed on garrison machines only and firestones do not
+  seem to have this issue.
+
+  This disables D-states changing for devices on root buses on Naples by
+  installing a config space access filter (copied from PHB4).