[PATCH v13 7/8] clk: qcom: cpu-8996: Add support to switch below 600Mhz

[ilia.lin@gmail.com]

From: Rajendra Nayak <rnayak@codeaurora.org>

The CPU clock controller's primary PLL operates on a single VCO range,
between 600MHz and 3GHz. However the CPUs do support OPPs with
frequencies between 300MHz and 600MHz. In order to support running the
CPUs at those frequencies we end up having to lock the PLL at twice the
rate and drive the CPU clk via the PLL/2 output and SMUX.

So for frequencies above 600MHz we follow the following path
 Primary PLL --> PLL_EARLY --> PMUX(1) --> CPU clk
and for frequencies between 300MHz and 600MHz we follow
 Primary PLL --> PLL/2 --> SMUX(1) --> PMUX(0) --> CPU clk

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Ilia Lin <ilialin@codeaurora.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>
---
 drivers/clk/qcom/clk-cpu-8996.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/qcom/clk-cpu-8996.c b/drivers/clk/qcom/clk-cpu-8996.c
index 620fdc2266ba..ff5c0a5740d2 100644
--- a/drivers/clk/qcom/clk-cpu-8996.c
+++ b/drivers/clk/qcom/clk-cpu-8996.c
@@ -68,6 +68,8 @@ enum _pmux_input {
 	NUM_OF_PMUX_INPUTS
 };
 
+#define DIV_2_THRESHOLD		600000000
+
 static const u8 prim_pll_regs[PLL_OFF_MAX_REGS] = {
        [PLL_OFF_L_VAL] = 0x04,
        [PLL_OFF_ALPHA_VAL] = 0x08,
@@ -95,10 +97,11 @@ static const u8 alt_pll_regs[PLL_OFF_MAX_REGS] = {
 
 static const struct alpha_pll_config hfpll_config = {
 	.l = 60,
-	.config_ctl_val = 0x200d4828,
+	.config_ctl_val = 0x200d4aa8,
 	.config_ctl_hi_val = 0x006,
 	.pre_div_mask = BIT(12),
 	.post_div_mask = 0x3 << 8,
+	.post_div_val = 0x1 << 8,
 	.main_output_mask = BIT(0),
 	.early_output_mask = BIT(3),
 };
@@ -140,7 +143,7 @@ static const struct alpha_pll_config altpll_config = {
 	.vco_mask = 0x3 << 20,
 	.config_ctl_val = 0x4001051b,
 	.post_div_mask = 0x3 << 8,
-	.post_div_val = 0x1,
+	.post_div_val = 0x1 << 8,
 	.main_output_mask = BIT(0),
 	.early_output_mask = BIT(3),
 };
@@ -181,6 +184,7 @@ struct clk_cpu_8996_mux {
 	u8	width;
 	struct notifier_block nb;
 	struct clk_hw	*pll;
+	struct clk_hw	*pll_div_2;
 	struct clk_regmap clkr;
 };
 
@@ -226,6 +230,13 @@ clk_cpu_8996_mux_determine_rate(struct clk_hw *hw, struct clk_rate_request *req)
 	struct clk_cpu_8996_mux *cpuclk = to_clk_cpu_8996_mux_hw(hw);
 	struct clk_hw *parent = cpuclk->pll;
 
+	if (cpuclk->pll_div_2 && req->rate < DIV_2_THRESHOLD) {
+		if (req->rate < (DIV_2_THRESHOLD / 2))
+			return -EINVAL;
+
+		parent = cpuclk->pll_div_2;
+	}
+
 	req->best_parent_rate = clk_hw_round_rate(parent, req->rate);
 	req->best_parent_hw = parent;
 
@@ -237,13 +248,19 @@ int cpu_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
 {
 	int ret;
 	struct clk_cpu_8996_mux *cpuclk = to_clk_cpu_8996_mux_nb(nb);
+	struct clk_notifier_data *cnd = data;
 
 	switch (event) {
 	case PRE_RATE_CHANGE:
 		ret = clk_cpu_8996_mux_set_parent(&cpuclk->clkr.hw, ALT_INDEX);
 		break;
 	case POST_RATE_CHANGE:
-		ret = clk_cpu_8996_mux_set_parent(&cpuclk->clkr.hw, PLL_INDEX);
+		if (cnd->new_rate < DIV_2_THRESHOLD)
+			ret = clk_cpu_8996_mux_set_parent(&cpuclk->clkr.hw,
+							  DIV_2_INDEX);
+		else
+			ret = clk_cpu_8996_mux_set_parent(&cpuclk->clkr.hw,
+							  PLL_INDEX);
 		break;
 	default:
 		ret = 0;
@@ -295,6 +312,7 @@ static struct clk_cpu_8996_mux pwrcl_pmux = {
 	.shift = 0,
 	.width = 2,
 	.pll = &pwrcl_pll.clkr.hw,
+	.pll_div_2 = &pwrcl_smux.clkr.hw,
 	.nb.notifier_call = cpu_clk_notifier_cb,
 	.clkr.hw.init = &(struct clk_init_data) {
 		.name = "pwrcl_pmux",
@@ -315,6 +333,7 @@ static struct clk_cpu_8996_mux perfcl_pmux = {
 	.shift = 0,
 	.width = 2,
 	.pll = &perfcl_pll.clkr.hw,
+	.pll_div_2 = &perfcl_smux.clkr.hw,
 	.nb.notifier_call = cpu_clk_notifier_cb,
 	.clkr.hw.init = &(struct clk_init_data) {
 		.name = "perfcl_pmux",
-- 
2.11.0