Re: [PATCH v2 4/5] clk: qcom: clk-alpha-pll: Add support for Lucid 5LPE PLL

From: Stephen Boyd
Date: Thu Dec 10 2020 - 15:37:49 EST

Quoting Vinod Koul (2020-12-07 22:47:01)
> diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
> index 564431130a76..6a399663d564 100644
> --- a/drivers/clk/qcom/clk-alpha-pll.c
> +++ b/drivers/clk/qcom/clk-alpha-pll.c
> @@ -146,6 +146,12 @@ EXPORT_SYMBOL_GPL(clk_alpha_pll_regs);
> /* LUCID PLL specific settings and offsets */
> #define LUCID_PCAL_DONE BIT(27)
>
> +/* LUCID 5LPE PLL specific settings and offsets */
> +#define LUCID_5LPE_PCAL_DONE BIT(11)
> +#define LUCID_5LPE_ENABLE_VOTE_RUN BIT(21)
> +#define LUCID_5LPE_PLL_LATCH_INPUT BIT(14)
> +#define LUCID_5LPE_ALPHA_PLL_ACK_LATCH BIT(13)

Sort these by bit or define name?

> +
> #define pll_alpha_width(p) \
> ((PLL_ALPHA_VAL_U(p) - PLL_ALPHA_VAL(p) == 4) ? \
> ALPHA_REG_BITWIDTH : ALPHA_REG_16BIT_WIDTH)
> @@ -1561,3 +1567,220 @@ const struct clk_ops clk_alpha_pll_postdiv_lucid_ops = {
> .set_rate = clk_alpha_pll_postdiv_fabia_set_rate,
> };
> EXPORT_SYMBOL_GPL(clk_alpha_pll_postdiv_lucid_ops);
> +
> +static int alpha_pll_lucid_5lpe_enable(struct clk_hw *hw)
> +{
> + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> + u32 val;
> + int ret;
> +
> + ret = regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &val);
> + if (ret)
> + return ret;
> +
> + /* If in FSM mode, just vote for it */
> + if (val & LUCID_5LPE_ENABLE_VOTE_RUN) {
> + ret = clk_enable_regmap(hw);
> + if (ret)
> + return ret;
> + return wait_for_pll_enable_lock(pll);
> + }
> +
> + /* Check if PLL is already enabled */

Yeah that's obvious, but then what?

> + ret = trion_pll_is_enabled(pll, pll->clkr.regmap);
> + if (ret < 0)
> + return ret;
> +
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), PLL_RESET_N, PLL_RESET_N);
> + if (ret)
> + return ret;
> +
> + /* Set operation mode to RUN */

This comment is worthless.

> + regmap_write(pll->clkr.regmap, PLL_OPMODE(pll), PLL_RUN);
> +
> + ret = wait_for_pll_enable_lock(pll);
> + if (ret)
> + return ret;
> +
> + /* Enable the PLL outputs */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll), PLL_OUT_MASK, PLL_OUT_MASK);
> + if (ret)
> + return ret;
> +
> + /* Enable the global PLL outputs */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), PLL_OUTCTRL, PLL_OUTCTRL);
> + if (ret)
> + return ret;
> +
> + /* Ensure that the write above goes through before returning. */
> + mb();

Regmap has a memory barrier in writel. Drop this.

> + return ret;
> +}
> +
> +static void alpha_pll_lucid_5lpe_disable(struct clk_hw *hw)
> +{
> + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> + u32 val;
> + int ret;
> +
> + ret = regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &val);
> + if (ret)
> + return;
> +
> + /* If in FSM mode, just unvote it */
> + if (val & LUCID_5LPE_ENABLE_VOTE_RUN) {
> + clk_disable_regmap(hw);
> + return;
> + }
> +
> + /* Disable the global PLL output */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), PLL_OUTCTRL, 0);
> + if (ret)
> + return;
> +
> + /* Disable the PLL outputs */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll), PLL_OUT_MASK, 0);
> + if (ret)
> + return;
> +
> + /* Place the PLL mode in STANDBY */
> + regmap_write(pll->clkr.regmap, PLL_OPMODE(pll), PLL_STANDBY);
> +}
> +
> +/*
> + * The Lucid 5LPE PLL requires a power-on self-calibration which happens
> + * when the PLL comes out of reset. Calibrate in case it is not completed.
> + */
> +static int alpha_pll_lucid_5lpe_prepare(struct clk_hw *hw)
> +{
> + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> + struct clk_hw *p;
> + u32 regval;

Can you use u32 val? And also include a patch to replace the couple
times where there is 'regval' in this file. The former is shorter and
used far more in qcom clk code.

> + int ret;
> +
> + /* Return early if calibration is not needed. */
> + regmap_read(pll->clkr.regmap, PLL_MODE(pll), &regval);
> + if (regval & LUCID_5LPE_PCAL_DONE)
> + return 0;
> +
> + p = clk_hw_get_parent(hw);
> + if (!p)
> + return -EINVAL;
> +
> + ret = alpha_pll_lucid_5lpe_enable(hw);
> + if (ret)
> + return ret;
> +
> + alpha_pll_lucid_5lpe_disable(hw);
> +
> + return 0;
> +}
> +
> +static int alpha_pll_lucid_5lpe_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long prate)
> +{
> + struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> + unsigned long rrate;
> + u32 regval, l;
> + u64 a;
> + int ret;
> +
> + rrate = alpha_pll_round_rate(rate, prate, &l, &a, ALPHA_REG_16BIT_WIDTH);
> +
> + /*
> + * Due to a limited number of bits for fractional rate programming, the
> + * rounded up rate could be marginally higher than the requested rate.
> + */
> + if (rrate > (rate + PLL_RATE_MARGIN) || rrate < rate) {
> + pr_err("Call set rate on the PLL with rounded rates!\n");
> + return -EINVAL;
> + }

Can we use alpha_pll_check_rate_margin()?

> +
> + regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
> + regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
> +
> + /* Latch the PLL input */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll),
> + LUCID_5LPE_PLL_LATCH_INPUT, LUCID_5LPE_PLL_LATCH_INPUT);
> + if (ret)
> + return ret;
> +
> + /* Wait for 2 reference cycles before checking the ACK bit. */
> + udelay(1);
> + regmap_read(pll->clkr.regmap, PLL_MODE(pll), &regval);
> + if (!(regval & LUCID_5LPE_ALPHA_PLL_ACK_LATCH)) {
> + pr_err("Lucid 5LPE PLL latch failed. Output may be unstable!\n");
> + return -EINVAL;
> + }
> +
> + /* Return the latch input to 0 */
> + ret = regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), LUCID_5LPE_PLL_LATCH_INPUT, 0);
> + if (ret)
> + return ret;
> +
> + if (clk_hw_is_enabled(hw)) {
> + ret = wait_for_pll_enable_lock(pll);
> + if (ret)
> + return ret;
> + }
> +
> + /* Wait for PLL output to stabilize */
> + udelay(100);
> + return 0;
> +}
> +
> +static int clk_lucid_5lpe_pll_postdiv_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + struct clk_alpha_pll_postdiv *pll = to_clk_alpha_pll_postdiv(hw);
> + int i, val = 0, div, ret;
> +
> + /*
> + * If the PLL is in FSM mode, then treat set_rate callback as a
> + * no-operation.
> + */
> + ret = regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &val);
> + if (ret)
> + return ret;
> +
> + if (val & LUCID_5LPE_ENABLE_VOTE_RUN)
> + return 0;
> +
> + if (!pll->post_div_table) {
> + pr_err("Missing the post_div_table for the PLL\n");

Can this be rolled into the loop below?

> + return -EINVAL;
> + }
> +
> + div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
> + for (i = 0; i < pll->num_post_div; i++) {

So that this finds nothing.

> + if (pll->post_div_table[i].div == div) {
> + val = pll->post_div_table[i].val;
> + break;
> + }
> + }

and then if val == -1 we return -EINVAL?

> +
> + return regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll),
> + (BIT(pll->width) - 1) << pll->post_div_shift,

Use GENMASK?

> + val << pll->post_div_shift);
> +}
> +