tree a2f753c253a18afe6cb09134b9a15d26eca3233b
parent 9891b75d96a199d1740fbd7df805abf23ae8f347
author Daniel Thompson <daniel.thompson@linaro.org> 1528187899 +0100
committer Nico Huber <nico.h@gmx.de> 1534540572 +0000

bitbang_spi: Add functions to optimize xfers

On systems where the overhead of getting/setting pins is much greater
than the half period (for example, USB bit banging) it significantly
boosts performance if we can bang more than one bit at the same time.
Add support for setting sck at the same time as mosi or miso activity.

The speed up varies depending on how much the overhead of
getting/setting pins dominates execution time. For a USB bit bang driver
running on a 7th generation Core i5, the time to probe drops from ~9.2
seconds to ~7.7 seconds when set_clk_set_mosi() is implemented.

Change-Id: Ic3430a9df34844cdfa82e109456be788eaa1789a
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-on: https://review.coreboot.org/26946
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Idwer Vollering <vidwer@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>