- Move DMA tag and map creature to at91_spi_activate() where the other
resource allocation also lives. [1]
- Flesh out at91_spi_deactivate(). [1]
- Work around the "Software Reset must be Written Twice" erratum.
- For now, run the bus at the slowest speed possible in order to work
around data corruption on transit even seen with 9 MHz on ETHERNUT5
(15 MHz maximum) and AT45DB321D (20 MHz maximum). This also serves as
a poor man's work-around for the "NPCSx rises if no data data is to be
transmitted" erratum of RM9200. Being able to use the appropriate bus
speed would require:
1) Adding a proper work-around for the RM9200 bug consisting of taking
the chip select control away from the SPI peripheral and managing it
directly as a GPIO line.
2) Taking the maximum frequencies supported by the actual board and the
slave devices into account and basing the whole thing on the master
clock instead of hardcoding a divisor as previously done.
3) Fixing the above mentioned data corruption.
- KASSERT that TX/RX command and data sizes match on transfers.
- Introduce a mutex ensuring that only one child device is running a SPI
transfer at a time. [1]
- Add preliminary, #ifdef'ed out support for setting the chip select. [1]
- Use the RX instead of the TX commando size when setting up the RX side
of a transfer.
- For controllers having SPI_SR_TXEMPTY, i.e. !RM9200, also wait for the
completion of the TX part of transfers before stopping the whole thing
again.
- Use DEVMETHOD_END. [1]
- Use NULL instead of 0 for pointers. [1, partially]
Additional testing by: Ian Lepore
Submitted by: Ian Lepore [1]
MFC after: 1 week
31a2c906d7