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

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>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/clk/bcm/clk-iproc-pll.c b/drivers/clk/bcm/clk-iproc-pll.c
index 7df010b2edcd..ab10819e2c09 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);