clk: qcom: clk-alpha-pll: Add support for Fabia PLL calibration

In the cases where the PLL is not calibrated the PLL could fail to lock.
Add support for prepare ops which would take care of the same.

Fabia PLL user/test control registers might required to be configured, so
add support for configuring them.

Signed-off-by: Taniya Das <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/qcom/clk-alpha-pll.c

···
 		regmap_write(regmap, PLL_CONFIG_CTL(pll),
 						config->config_ctl_val);
 
+	if (config->config_ctl_hi_val)
+		regmap_write(regmap, PLL_CONFIG_CTL_U(pll),
+						config->config_ctl_hi_val);
+
+	if (config->user_ctl_val)
+		regmap_write(regmap, PLL_USER_CTL(pll), config->user_ctl_val);
+
+	if (config->user_ctl_hi_val)
+		regmap_write(regmap, PLL_USER_CTL_U(pll),
+						config->user_ctl_hi_val);
+
+	if (config->test_ctl_val)
+		regmap_write(regmap, PLL_TEST_CTL(pll),
+						config->test_ctl_val);
+
+	if (config->test_ctl_hi_val)
+		regmap_write(regmap, PLL_TEST_CTL_U(pll),
+						config->test_ctl_hi_val);
+
 	if (config->post_div_mask) {
 		mask = config->post_div_mask;
 		val = config->post_div_val;
···
 	return __clk_alpha_pll_update_latch(pll);
 }
 
+static int alpha_pll_fabia_prepare(struct clk_hw *hw)
+{
+	struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
+	const struct pll_vco *vco;
+	struct clk_hw *parent_hw;
+	unsigned long cal_freq, rrate;
+	u32 cal_l, val, alpha_width = pll_alpha_width(pll);
+	u64 a;
+	int ret;
+
+	/* Check if calibration needs to be done i.e. PLL is in reset */
+	ret = regmap_read(pll->clkr.regmap, PLL_MODE(pll), &val);
+	if (ret)
+		return ret;
+
+	/* Return early if calibration is not needed. */
+	if (val & PLL_RESET_N)
+		return 0;
+
+	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;
+	}
+
+	cal_freq = DIV_ROUND_CLOSEST((pll->vco_table[0].min_freq +
+				pll->vco_table[0].max_freq) * 54, 100);
+
+	parent_hw = clk_hw_get_parent(hw);
+	if (!parent_hw)
+		return -EINVAL;
+
+	rrate = alpha_pll_round_rate(cal_freq, clk_hw_get_rate(parent_hw),
+					&cal_l, &a, alpha_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 > (cal_freq + FABIA_PLL_RATE_MARGIN) || rrate < cal_freq)
+		return -EINVAL;
+
+	/* Setup PLL for calibration frequency */
+	regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), cal_l);
+
+	/* Bringup the PLL at calibration frequency */
+	ret = clk_alpha_pll_enable(hw);
+	if (ret) {
+		pr_err("alpha pll calibration failed\n");
+		return ret;
+	}
+
+	clk_alpha_pll_disable(hw);
+
+	return 0;
+}
+
 const struct clk_ops clk_alpha_pll_fabia_ops = {
+	.prepare = alpha_pll_fabia_prepare,
 	.enable = alpha_pll_fabia_enable,
 	.disable = alpha_pll_fabia_disable,
 	.is_enabled = clk_alpha_pll_is_enabled,

drivers/clk/qcom/clk-alpha-pll.h

···
 	u32 alpha_hi;
 	u32 config_ctl_val;
 	u32 config_ctl_hi_val;
+	u32 user_ctl_val;
+	u32 user_ctl_hi_val;
+	u32 test_ctl_val;
+	u32 test_ctl_hi_val;
 	u32 main_output_mask;
 	u32 aux_output_mask;
 	u32 aux2_output_mask;