tree ea6e79554893a014d014f9fd49d9de62e23c10ff
parent 842aa5bcad19770a7a0832e1b25ad845b06a37e1
author Jerry Huang <Chang-Ming.Huang@freescale.com> 1320304686 +0800
committer Kumar Gala <galak@kernel.crashing.org> 1321019334 -0600

powerpc/mpc85xx: Set SYSCLK to the required frequency

For ICS307-02, there is one general expression to generate SYSCLK:
CLK1Frequency = InputFrequency * 2 * (VDW + 8) / ((RDW + 2) * OD)

If we want the required frequency for SYSCLK, we must find one solution
to generate this frequency, this solution includes VDW, RDW and OD.
For OD, there are only eight option value: 10, 2, 8, 4, 5, 7, 3, 6.
For RDW, the range is 1 to 127.
For VDW, the range is 4 to 511.

First, we use one OD, RDW and required SYSCLK to calculate the VDW,
if VDW is in it's range, we will calculate the CLK1Frequency with
the OD, RDW and VDW calculated, and we will check this percent
(CLK1Frequency / required SYSCLK), and the precision is 1/1000.
if the percent is less than 1/1000, we think the CLK1Frequency is we want.
Otherwise, We will continue to calculate it with the next OD and RDW.

Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>