[PATCH v4 01/10] clk: qcom: clk-alpha-pll: Add support for dynamic update for slewing PLLs

Taniya Das
2025-01-19T10:23:33Z

The alpha PLLs which slew to a new frequency at runtime would require
the PLL to calibrate at the mid point of the VCO. Add the new PLL ops
which can support the slewing of the PLL to a new frequency.

Reviewed-by: Imran Shaik <quic_imrashai@quicinc.com>
Signed-off-by: Taniya Das <quic_tdas@quicinc.com>
---
drivers/clk/qcom/clk-alpha-pll.c | 170 +++++++++++++++++++++++++++++++++++++++
drivers/clk/qcom/clk-alpha-pll.h | 1 +
2 files changed, 171 insertions(+)

diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
index 9a65d14acf71c97912664be4f6f78891cab4afa3..ac2327d6cc48a3fe2676108028ad9250ea435e86 100644
--- a/drivers/clk/qcom/clk-alpha-pll.c
+++ b/drivers/clk/qcom/clk-alpha-pll.c
@@ -2940,3 +2940,173 @@ const struct clk_ops clk_alpha_pll_regera_ops = {
.set_rate = clk_zonda_pll_set_rate,
};
EXPORT_SYMBOL_GPL(clk_alpha_pll_regera_ops);
+
+static int clk_alpha_pll_slew_update(struct clk_alpha_pll *pll)
+{
+ int ret;
+ u32 val;
+
+ regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), PLL_UPDATE, PLL_UPDATE);
+ regmap_read(pll->clkr.regmap, PLL_MODE(pll), &val);
+
+ ret = wait_for_pll_update(pll);
+ if (ret)
+ return ret;
+ /*
+ * Hardware programming mandates a wait of at least 570ns before polling the LOCK
+ * detect bit. Have a delay of 1us just to be safe.
+ */
+ mb();
+ udelay(1);
+
+ return wait_for_pll_enable_lock(pll);
+}
+
+static int clk_alpha_pll_slew_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
+ unsigned long freq_hz;
+ const struct pll_vco *curr_vco, *vco;
+ u32 l, alpha_width = pll_alpha_width(pll);
+ u64 a;
+
+ freq_hz = alpha_pll_round_rate(rate, parent_rate, &l, &a, alpha_width);
+ if (freq_hz != rate) {
+ pr_err("alpha_pll: Call clk_set_rate with rounded rates!\n");
+ return -EINVAL;
+ }
+
+ curr_vco = alpha_pll_find_vco(pll, clk_hw_get_rate(hw));
+ if (!curr_vco) {
+ pr_err("alpha pll: not in a valid vco range\n");
+ return -EINVAL;
+ }
+
+ vco = alpha_pll_find_vco(pll, freq_hz);
+ if (!vco) {
+ pr_err("alpha pll: not in a valid vco range\n");
+ return -EINVAL;
+ }
+
+ /*
+ * Dynamic pll update will not support switching frequencies across
+ * vco ranges. In those cases fall back to normal alpha set rate.
+ */
+ if (curr_vco->val != vco->val)
+ return clk_alpha_pll_set_rate(hw, rate, parent_rate);
+
+ a = a << (ALPHA_REG_BITWIDTH - ALPHA_BITWIDTH);
+
+ regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL_U(pll), a >> 32);
+
+ /* Ensure that the write above goes through before proceeding. */
+ mb();
+
+ if (clk_hw_is_enabled(hw))
+ return clk_alpha_pll_slew_update(pll);
+
+ return 0;
+}
+
+/*
+ * Slewing plls should be bought up at frequency which is in the middle of the
+ * desired VCO range. So after bringing up the pll at calibration freq, set it
+ * back to desired frequency(that was set by previous clk_set_rate).
+ */
+static int clk_alpha_pll_calibrate(struct clk_hw *hw)
+{
+ unsigned long calibration_freq, freq_hz;
+ struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
+ struct clk_hw *parent;
+ const struct pll_vco *vco;
+ u32 l, alpha_width = pll_alpha_width(pll);
+ int rc;
+ u64 a;
+
+ parent = clk_hw_get_parent(hw);
+ if (!parent) {
+ pr_err("alpha pll: no valid parent found\n");
+ return -EINVAL;
+ }
+
+ vco = alpha_pll_find_vco(pll, clk_hw_get_rate(hw));
+ if (!vco) {
+ pr_err("alpha pll: not in a valid vco range\n");
+ return -EINVAL;
+ }
+
+ /*
+ * As during slewing plls vco_sel won't be allowed to change, vco table
+ * should have only one entry table, i.e. index = 0, find the
+ * calibration frequency.
+ */
+ calibration_freq = (pll->vco_table[0].min_freq + pll->vco_table[0].max_freq) / 2;
+
+ freq_hz = alpha_pll_round_rate(calibration_freq, clk_hw_get_rate(parent),
+ &l, &a, alpha_width);
+ if (freq_hz != calibration_freq) {
+ pr_err("alpha_pll: call clk_set_rate with rounded rates!\n");
+ return -EINVAL;
+ }
+
+ /* Setup PLL for calibration frequency */
+ a <<= (ALPHA_REG_BITWIDTH - ALPHA_BITWIDTH);
+
+ regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL_U(pll), a >> 32);
+
+ regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll), PLL_VCO_MASK << PLL_VCO_SHIFT,
+ vco->val << PLL_VCO_SHIFT);
+
+ /* Bringup the pll at calibration frequency */
+ rc = clk_alpha_pll_enable(hw);
+ if (rc) {
+ pr_err("alpha pll calibration failed\n");
+ return rc;
+ }
+
+ /*
+ * PLL is already running at calibration frequency.
+ * So slew pll to the previously set frequency.
+ */
+ freq_hz = alpha_pll_round_rate(clk_hw_get_rate(hw),
+ clk_hw_get_rate(parent), &l, &a, alpha_width);
+
+ pr_debug("pll %s: setting back to required rate %lu, freq_hz %ld\n",
+ clk_hw_get_name(hw), clk_hw_get_rate(hw), freq_hz);
+
+ /* Setup the PLL for the new frequency */
+ a <<= (ALPHA_REG_BITWIDTH - ALPHA_BITWIDTH);
+
+ regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
+ regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL_U(pll), a >> 32);
+
+ regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll), PLL_ALPHA_EN, PLL_ALPHA_EN);
+
+ return clk_alpha_pll_slew_update(pll);
+}
+
+static int clk_alpha_pll_slew_enable(struct clk_hw *hw)
+{
+ int rc;
+
+ rc = clk_alpha_pll_calibrate(hw);
+ if (rc)
+ return rc;
+
+ return clk_alpha_pll_enable(hw);
+}
+
+const struct clk_ops clk_alpha_pll_slew_ops = {
+ .enable = clk_alpha_pll_slew_enable,
+ .disable = clk_alpha_pll_disable,
+ .recalc_rate = clk_alpha_pll_recalc_rate,
+ .round_rate = clk_alpha_pll_round_rate,
+ .set_rate = clk_alpha_pll_slew_set_rate,
+};
+EXPORT_SYMBOL(clk_alpha_pll_slew_ops);
diff --git a/drivers/clk/qcom/clk-alpha-pll.h b/drivers/clk/qcom/clk-alpha-pll.h
index 79aca8525262211ae5295245427d4540abf1e09a..1d19001605eb10fd8ae8041c56d951e928cbbe9f 100644
--- a/drivers/clk/qcom/clk-alpha-pll.h
+++ b/drivers/clk/qcom/clk-alpha-pll.h
@@ -204,6 +204,7 @@ extern const struct clk_ops clk_alpha_pll_rivian_evo_ops;
#define clk_alpha_pll_postdiv_rivian_evo_ops clk_alpha_pll_postdiv_fabia_ops

extern const struct clk_ops clk_alpha_pll_regera_ops;
+extern const struct clk_ops clk_alpha_pll_slew_ops;

void clk_alpha_pll_configure(struct clk_alpha_pll *pll, struct regmap *regmap,
const struct alpha_pll_config *config);

--
2.45.2