With closed loop support, the clock rate of the DFLL can be adjusted.

The oscillator itself in the DFLL is a free-running oscillator whose
rate is directly determined the supply voltage. However, the DFLL
module contains logic to compare the DFLL output rate to a fixed
reference clock (51 MHz) and make a decision to either lower or raise
the DFLL supply voltage. The DFLL module can then autonomously change
the supply voltage by communicating with an off-chip PMIC via either I2C
or PWM signals. This driver currently supports only I2C.
Signed-off-by: NTuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: NMikko Perttunen <mikko.perttunen@kapsi.fi>
Acked-by: NPeter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: NMichael Turquette <mturquette@linaro.org>
Signed-off-by: NThierry Reding <treding@nvidia.com>

Add shared code to support the Tegra DFLL clocksource in open-loop
mode. This root clocksource is present on the Tegra124 SoCs. The
DFLL is the intended primary clock source for the fast CPU cluster.

This code is very closely based on a patch by Paul Walmsley from
December (http://comments.gmane.org/gmane.linux.ports.tegra/15273),
which in turn comes from the internal driver by originally created
by Aleksandr Frid <afrid@nvidia.com>.

Subsequent patches will add support for closed loop mode and drivers
for the Tegra124 fast CPU cluster DFLL devices, which rely on this
code.
Signed-off-by: NPaul Walmsley <pwalmsley@nvidia.com>
Signed-off-by: NTuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: NMikko Perttunen <mikko.perttunen@kapsi.fi>
Acked-by: NPeter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: NMichael Turquette <mturquette@linaro.org>
Signed-off-by: NThierry Reding <treding@nvidia.com>