skiboot 5.9-rc4 release notes

Signed-off-by: Stewart Smith <[email protected]>

doc/release-notes/skiboot-5.9-rc4.rst

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+.. _skiboot-5.9-rc4:
+
+skiboot-5.9-rc4
+===============
+
+skiboot v5.9-rc4 was released on Thursday October 19th 2017. It is the fourth
+release candidate of skiboot 5.9, which will become the new stable release
+of skiboot following the 5.8 release, first released August 31st 2017.
+
+skiboot v5.9-rc4 contains all bug fixes as of :ref:`skiboot-5.4.8`
+and :ref:`skiboot-5.1.21` (the currently maintained stable releases). We
+do not currently expect to do any 5.8.x stable releases.
+
+For how the skiboot stable releases work, see :ref:`stable-rules` for details.
+
+The current plan is to cut the final 5.9 by October 20th, with skiboot 5.9
+being for all POWER8 and POWER9 platforms in op-build v1.20 (Due October 18th,
+so we're running a bit behind there).
+This release will be targetted to early POWER9 systems.
+
+Over :ref:`skiboot-5.9-rc3`, we have the following changes:
+
+- phb4: Fix PCIe GEN4 on DD2.1 and above
+
+  In this change:
+      eef0e197ab PHB4: Default to PCIe GEN3 on POWER9 DD2.00
+
+  We clamped DD2.00 parts to GEN3 but unfortunately this change also
+  applies to DD2.1 and above.
+
+  This fixes this to only apply to DD2.00.
+- occ-sensors : Add OCC inband sensor region to exports
+  (useful for debugging)
+
+Two SRESET fixes:
+
+- core: direct-controls: Fix clearing of special wakeup
+
+  'special_wakeup_count' is incremented on successfully asserting
+  special wakeup. So we will never clear the special wakeup if we
+  check 'special_wakeup_count' to be zero. Fix this issue by checking
+  the 'special_wakeup_count' to 1 in dctl_clear_special_wakeup().
+- core/direct-controls: increase special wakeup timeout on POWER9
+
+  Some instances have been observed where the special wakeup assert
+  times out. The current timeout is too short for deeper sleep states.
+  Hostboot uses 100ms, so match that.