[PATCH v1 3/4] clk: iproc: Allow plls to do minor rate changes without reset

Lori Hikichi
2017-08-14T19:00:21Z

From: Lori Hikichi <lhikichi@broadcom.com>

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>
---
drivers/clk/bcm/clk-iproc-pll.c | 47 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/drivers/clk/bcm/clk-iproc-pll.c b/drivers/clk/bcm/clk-iproc-pll.c
index 7df010b..ab10819 100644
--- a/drivers/clk/bcm/clk-iproc-pll.c
+++ b/drivers/clk/bcm/clk-iproc-pll.c
@@ -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);

--
1.9.1