[PATCH v1 3/4] clk: iproc: Allow plls to do minor rate changes without reset
From: Lori Hikichi <hidden>
Date: 2017-08-14 19:00:21
Also in:
linux-clk, lkml
Subsystem:
common clk framework, the rest · Maintainers:
Michael Turquette, Stephen Boyd, Linus Torvalds
From: Lori Hikichi <redacted> 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 <redacted> --- 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