skiboot 6.0.3 was released on Wednesday May 23rd, 2018. It replaces 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 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:
it doesn’t do what it’s supposed to, and
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.