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clk: iproc: Allow plls to do minor rate changes without reset

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The iproc plls are capable of doing small rate changes without the
need for a full reset and re-lock procedure.  This feature will
allow for small tweaks to the PLL rate to occur smoothly.

Signed-off-by: Lori Hikichi <lori.hikichi@broadcom.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Lori Hikichi 2017-08-14 12:00:40 -07:00 committed by Stephen Boyd
parent 85151a6b0b
commit f3f739c93c
1 changed files with 47 additions and 0 deletions
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47
drivers/clk/bcm/clk-iproc-pll.c
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@ -285,6 +285,40 @@ static void __pll_bring_out_reset(struct iproc_pll *pll, unsigned int kp,
iproc_pll_write(pll, pll->control_base, reset->offset, val);
}
/*
* Determines if the change to be applied to the PLL is minor (just an update
* or the fractional divider). If so, then we can avoid going through a
* disruptive reset and lock sequence.
*/
static bool pll_fractional_change_only(struct iproc_pll *pll,
struct iproc_pll_vco_param *vco)
{
const struct iproc_pll_ctrl *ctrl = pll->ctrl;
u32 val;
u32 ndiv_int;
unsigned int pdiv;
/* PLL needs to be locked */
val = readl(pll->status_base + ctrl->status.offset);
if ((val & (1 << ctrl->status.shift)) == 0)
return false;
val = readl(pll->control_base + ctrl->ndiv_int.offset);
ndiv_int = (val >> ctrl->ndiv_int.shift) &
bit_mask(ctrl->ndiv_int.width);
if (ndiv_int != vco->ndiv_int)
return false;
val = readl(pll->control_base + ctrl->pdiv.offset);
pdiv = (val >> ctrl->pdiv.shift) & bit_mask(ctrl->pdiv.width);
if (pdiv != vco->pdiv)
return false;
return true;
}
static int pll_set_rate(struct iproc_clk *clk, struct iproc_pll_vco_param *vco,
unsigned long parent_rate)
{
@ -333,6 +367,19 @@ static int pll_set_rate(struct iproc_clk *clk, struct iproc_pll_vco_param *vco,
return ret;
}
if (pll_fractional_change_only(clk->pll, vco)) {
/* program fractional part of NDIV */
if (ctrl->flags & IPROC_CLK_PLL_HAS_NDIV_FRAC) {
val = readl(pll->control_base + ctrl->ndiv_frac.offset);
val &= ~(bit_mask(ctrl->ndiv_frac.width) <<
ctrl->ndiv_frac.shift);
val |= vco->ndiv_frac << ctrl->ndiv_frac.shift;
iproc_pll_write(pll, pll->control_base,
ctrl->ndiv_frac.offset, val);
return 0;
}
}
/* put PLL in reset */
__pll_put_in_reset(pll);