spi/rockchip: Add device tree property to configure Rx Sample Delay
authorJulius Werner <jwerner@chromium.org>
Thu, 26 Mar 2015 23:30:25 +0000 (16:30 -0700)
committerMark Brown <broonie@kernel.org>
Fri, 27 Mar 2015 00:42:21 +0000 (17:42 -0700)
commit76b17e6e4923e4138ed9a4d480cba148ff239dc9
treedf93239b9d52f60f9031e3b66aefd5a5153e454f
parent2291793cc4c6b1251e28a4ff0f98041147d57e96
spi/rockchip: Add device tree property to configure Rx Sample Delay

We have found that we can sometimes see read failures on boards with
high-capacitance SPI lines. It seems that the controller samples the Rx
data line too early, and its register interface has an "Rx Sample Delay"
setting to fine-tune against this issue.

This patch adds a new optional device tree entry that can configure this
delay in terms of nanoseconds. The kernel will calculate the
best-fitting amount of parent clock ticks to program the controller with
based on that.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Documentation/devicetree/bindings/spi/spi-rockchip.txt
drivers/spi/spi-rockchip.c