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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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43
arch/arm/mach-omap2/clock34xx.c
View File

@ -150,6 +150,49 @@ const struct clkops clkops_omap3430es2_hsotgusb_wait = {
.find_companion = omap2_clk_dflt_find_companion,
};
/**
* omap36xx_pwrdn_clk_enable_with_hsdiv_restore - enable clocks suffering
* from HSDivider PWRDN problem Implements Errata ID: i556.
* @clk: DPLL output struct clk
*
* 3630 only: dpll3_m3_ck, dpll4_m2_ck, dpll4_m3_ck, dpll4_m4_ck,
* dpll4_m5_ck & dpll4_m6_ck dividers gets loaded with reset
* valueafter their respective PWRDN bits are set. Any dummy write
* (Any other value different from the Read value) to the
* corresponding CM_CLKSEL register will refresh the dividers.
*/
static int omap36xx_pwrdn_clk_enable_with_hsdiv_restore(struct clk *clk)
{
u32 dummy_v, orig_v, clksel_shift;
int ret;
/* Clear PWRDN bit of HSDIVIDER */
ret = omap2_dflt_clk_enable(clk);
/* Restore the dividers */
if (!ret) {
clksel_shift = __ffs(clk->parent->clksel_mask);
orig_v = __raw_readl(clk->parent->clksel_reg);
dummy_v = orig_v;
/* Write any other value different from the Read value */
dummy_v ^= (1 << clksel_shift);
__raw_writel(dummy_v, clk->parent->clksel_reg);
/* Write the original divider */
__raw_writel(orig_v, clk->parent->clksel_reg);
}
return ret;
}
const struct clkops clkops_omap36xx_pwrdn_with_hsdiv_wait_restore = {
.enable = omap36xx_pwrdn_clk_enable_with_hsdiv_restore,
.disable = omap2_dflt_clk_disable,
.find_companion = omap2_clk_dflt_find_companion,
.find_idlest = omap2_clk_dflt_find_idlest,
};
const struct clkops omap3_clkops_noncore_dpll_ops = {
.enable = omap3_noncore_dpll_enable,
.disable = omap3_noncore_dpll_disable,

3
arch/arm/mach-omap2/clock34xx.h
View File

@ -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

19
arch/arm/mach-omap2/clock34xx_data.c
View File

@ -3358,6 +3358,25 @@ int __init omap3xxx_clk_init(void)
}
}
if (cpu_is_omap3630()) {
/*
* For 3630: override clkops_omap2_dflt_wait for the
* clocks affected from PWRDN reset Limitation
*/
dpll3_m3x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
dpll4_m2x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
dpll4_m3x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
dpll4_m4x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
dpll4_m5x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
dpll4_m6x2_ck.ops =
&clkops_omap36xx_pwrdn_with_hsdiv_wait_restore;
}
clk_init(&omap2_clk_functions);
for (c = omap3xxx_clks; c < omap3xxx_clks + ARRAY_SIZE(omap3xxx_clks); c++)