The OPAL firmware only supports a finite number of in-flight asynchronous
operations. Rather than have each subsystem try to manage its own, use a
central management service to hand out tokens.
More work can be done to improve asynchronous behavior, such as funneling
things through a future OPAL heartbeat handler, but capabilities will be
added as needed.
Augment the existing consumers (i2c and sensors) to use this new API.
MFC after: 4 weeks
* FreeBSD stores addresses in 8 bit format, but the OPAL API requires the 7-bit
address, and encodes the direction elsewhere. Behave like other i2c drivers,
and shift accordingly.
* The OPAL API can already handle multiple requests in flight. Change the async
token to be private to the thread, so as not to stomp across i2c accesses,
remove the limitation error message, and use the correct message index to
transfer all messages in the list.
* Micro-optimize the async handler to not continuously call pmap_kextract() when
spin-waiting for the operation to complete.
This has been tested by hexdumping an EEPROM attached via the icee(4) driver.
ofw_iicbus already has attachments on iichb. Rather than adding an explicit
attachment onto opal_i2c, simply change the exposed name of the OPAL i2c bus
to 'iichb'.
Add I2C OPAL driver and a set of dummy-ones to allow
all I2C things on Power8 to attach.
TODO: better async token management
Submitted by: Wojciech Macek <wma@semihalf.com>
Obtained from: Semihalf
Sponsored by: IBM, QCM Technologies
