Currently the cadence SPI driver does the SPI clock configuration (setup CPOL
and CPHA) in the prepare_transfer_hardware() callback. The
prepare_transfer_hardware() callback is only called though when the controller
transitions from a idle state to a non-idle state. Such a transitions happens
when the message queue goes from empty to non-empty. If multiple messages from
different SPI slaves with different clock settings are in the message queue the
clock settings will not be properly updated when switching from one slave device
to another. Instead do the updating of the clock configuration in the
prepare_message() callback which will be called for each individual message.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
It seems that the cadence SPI controller does not immediately change the clock
polarity setting when writing the CR register. Instead the change is delayed
until the next transfer starts. This happens after the chip select line has
already been asserted. As a result the first transfer after a clock polarity
change will generate spurious clock transitions which typically results in the
SPI slave not being able to properly understand the message. Toggling the ER
register seems to cause the SPI controller to apply the clock polarity changes,
so implement this as a workaround to fix the issue.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
Add driver for Cadence SPI controller. This is used in Xilinx Zynq.
Signed-off-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
