spi: spi-geni-qcom: Get rid of most overhead in prepare_message()

There's a bunch of overhead in spi-geni-qcom's prepare_message.  Get
rid of it.  Before this change spi_geni_prepare_message() took around
14.5 us.  After this change, spi_geni_prepare_message() takes about
1.75 us (as measured by ftrace).

What's here:
* We're always in FIFO mode, so no need to call it for every transfer.
  This avoids a whole ton of readl/writel calls.
* We don't need to write a whole pile of config registers if the mode
  isn't changing.  Cache the last mode and only do the work if needed.
* For several registers we were trying to do read/modify/write, but
  there was no reason.  The registers only have one thing in them, so
  just write them.

Acked-by: Mark Brown <[email protected]>
Reviewed-by: Akash Asthana <[email protected]>
Signed-off-by: Douglas Anderson <[email protected]>
Link: https://lore.kernel.org/r/20200701174506.3.I2b3d7aeb1ea622335482cce60c58d2f8381e61dd@changeid
Signed-off-by: Bjorn Andersson <[email protected]>

0 files changed, 0 insertions, 0 deletions