[PATCH 06/13] clk: qcom: cpu-8996: simplify the cpu_clk_notifier_cb

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

- Do not use the Alt PLL completely. Switch to smux when necessary to
  prevent overvolting
- Restore the parent in case the rate change aborts for some reason
- Do not duplicate resetting the parent in set_parent operation.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/clk/qcom/clk-cpu-8996.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/clk/qcom/clk-cpu-8996.c b/drivers/clk/qcom/clk-cpu-8996.c
index 7e5246ca7e7f..ee7e18b37832 100644
--- a/drivers/clk/qcom/clk-cpu-8996.c
+++ b/drivers/clk/qcom/clk-cpu-8996.c
@@ -506,27 +506,34 @@ static int cpu_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
 {
 	struct clk_cpu_8996_pmux *cpuclk = to_clk_cpu_8996_pmux_nb(nb);
 	struct clk_notifier_data *cnd = data;
-	int ret;
 
 	switch (event) {
 	case PRE_RATE_CHANGE:
-		ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, ALT_INDEX);
 		qcom_cpu_clk_msm8996_acd_init(base);
+
+		/*
+		 * Avoid overvolting. clk_core_set_rate_nolock() walks from top
+		 * to bottom, so it will change the rate of the PLL before
+		 * chaging the parent of PMUX. This can result in pmux getting
+		 * clocked twice the expected rate.
+		 *
+		 * Manually switch to PLL/2 here.
+		 */
+		if (cnd->new_rate < DIV_2_THRESHOLD &&
+		    cnd->old_rate > DIV_2_THRESHOLD)
+			clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, SMUX_INDEX);
+
 		break;
-	case POST_RATE_CHANGE:
-		if (cnd->new_rate < DIV_2_THRESHOLD)
-			ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
-							   SMUX_INDEX);
-		else
-			ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
-							   ACD_INDEX);
-		break;
+	case ABORT_RATE_CHANGE:
+		/* Revert manual change */
+		if (cnd->new_rate < DIV_2_THRESHOLD &&
+		    cnd->old_rate > DIV_2_THRESHOLD)
+			clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, ACD_INDEX);
 	default:
-		ret = 0;
 		break;
 	}
 
-	return notifier_from_errno(ret);
+	return NOTIFY_OK;
 };
 
 static int qcom_cpu_clk_msm8996_driver_probe(struct platform_device *pdev)
-- 
2.30.2