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OMAP3630: Clock: Workaround for DPLL HS divider limitation

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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 <mturquette@ti.com>
Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com>
Signed-off-by: Vijaykumar GN <vijaykumar.gn@ti.com>
[paul@pwsan.com: updated patch to apply; made workaround function static;
 marked as being 36xx-specific]
Signed-off-by: Paul Walmsley <paul@pwsan.com>
This commit is contained in:
Mike Turquette
2010-02-24 12:06:00 -07:00
committed by Paul Walmsley
parent c23a97d377
commit a7e069fc5a
3 changed files with 65 additions and 0 deletions
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3
arch/arm/mach-omap2/clock34xx.h
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@@ -26,4 +26,7 @@ extern const struct clkops omap3_clkops_noncore_dpll_ops;
extern const struct clkops clkops_am35xx_ipss_module_wait;
extern const struct clkops clkops_am35xx_ipss_wait;
/* OMAP36xx-specific clkops */
extern const struct clkops clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
#endif