OMAP3630: Clock: Workaround for DPLL HS divider limitation

This patch implements a workaround for the DPLL HS divider limitation
in OMAP3630 as given by Errata ID: i556.

Errata:
When PWRDN bit is set, it resets the internal HSDIVIDER divide-by value (Mx).
The reset value gets loaded instead of the previous value.
The following HSDIVIDERs exhibit above behavior:
. DPLL4 : M6 / M5 / M4 / M3 / M2 (CM_CLKEN_PLL[31:26] register bits)
. DPLL3 : M3 (CM_CLKEN_PLL[12] register bit).

Work Around:
It is mandatory to apply the following sequence to ensure the write
value will
be loaded in DPLL HSDIVIDER FSM:
The global sequence when using PWRDN bit is the following:
. Disable Mx HSDIVIDER clock output related functional clock enable bits
        (in CM_FCLKEN_xxx / CM_ICLKEN_xxx)
. Enable PWRDN bit of HSDIVIDER
. Disable PWRDN bit of HSDIVIDER
. Read current HSDIVIDER register value
. Write different value in HSDIVIDER register
. Write expected value in HSDIVIDER register
. Enable Mx HSDIVIDER clock output related functional clocks
        (CM_FCLKEN_xxx / CM_ICLKEN_xxx)

Signed-off-by: Mike Turquette <[email protected]>
Signed-off-by: Vishwanath BS <[email protected]>
Signed-off-by: Vijaykumar GN <[email protected]>
[[email protected]: updated patch to apply; made workaround function static;
 marked as being 36xx-specific]
Signed-off-by: Paul Walmsley <[email protected]>

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