skiboot 6.0.3 release notes

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

doc/release-notes/skiboot-6.0.3.rst

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+.. _skiboot-6.0.3:
+
+=============
+skiboot-6.0.3
+=============
+
+skiboot 6.0.3 was released on Wednesday May 23rd, 2018. It replaces
+:ref:`skiboot-6.0.2` as the current stable release in the 6.0.x series.
+
+It is recommended that 6.0.3 be used instead of any previous 6.0.x version.
+
+Over :ref:`skiboot-6.0.3`, we have bug fixes related to i2c booting in
+secure mode, and general functionality with a TPM present. These changes are:
+
+- 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:
+
+     a) it doesn't do what it's supposed to, and
+     b) 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.
+- 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.