linux-kernel - [PATCH v2 5/5] clk: qcom: ipq4019: Added the cpu clock frequency change notifier

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Message-Id: <1466516962-18087-6-git-send-email-absahu@codeaurora.org>
Date:	Tue, 21 Jun 2016 19:19:22 +0530
From:	Abhishek Sahu <absahu@...eaurora.org>
To:	andy.gross@...aro.org, david.brown@...aro.org,
	sboyd@...eaurora.org, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk
Cc:	mturquette@...libre.com, galak@...eaurora.org,
	pradeepb@...eaurora.org, mmcclint@...eaurora.org,
	varada@...eaurora.org, sricharan@...eaurora.org,
	architt@...eaurora.org, ntelkar@...eaurora.org,
	linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, Abhishek Sahu <absahu@...eaurora.org>
Subject: [PATCH v2 5/5] clk: qcom: ipq4019: Added the cpu clock frequency change notifier

The current driver code gives the crash or gets hang while switching
the CPU frequency some time. The APSS CPU Clock divider is not glitch
free so it the APPS clock need to be switched for stable clock during
the change.

This patch adds the frequency change notifier for APSS CPU clock. It
changes the parent of this clock to stable PLL FEPLL500 when it gets
for PRE_RATE_CHANGE event. This event will be generated before actual
clock set operations. The clock set operation will again change its
corresponding parent by getting the same from frequency table.

Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
---
 drivers/clk/qcom/gcc-ipq4019.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/qcom/gcc-ipq4019.c b/drivers/clk/qcom/gcc-ipq4019.c
index df159c2..3c014f7 100644
--- a/drivers/clk/qcom/gcc-ipq4019.c
+++ b/drivers/clk/qcom/gcc-ipq4019.c
@@ -1740,9 +1740,34 @@ static const struct of_device_id gcc_ipq4019_match_table[] = {
 };
 MODULE_DEVICE_TABLE(of, gcc_ipq4019_match_table);
 
+int cpu_clk_notifier_fn(struct notifier_block *nb,
+			unsigned long action, void *data)
+{
+	int err = 0;
+
+	if (action == PRE_RATE_CHANGE) {
+		err = clk_rcg2_ops.set_parent(&apps_clk_src.clkr.hw,
+							P_FEPLL500);
+	}
+
+	return notifier_from_errno(err);
+}
+
+struct notifier_block cpu_clk_notifier = {
+	.notifier_call = cpu_clk_notifier_fn,
+};
+
 static int gcc_ipq4019_probe(struct platform_device *pdev)
 {
-	return qcom_cc_probe(pdev, &gcc_ipq4019_desc);
+	int err;
+
+	err = qcom_cc_probe(pdev, &gcc_ipq4019_desc);
+
+	if (!err)
+		clk_notifier_register(apps_clk_src.clkr.hw.clk,
+					&cpu_clk_notifier);
+
+	return err;
 }
 
 static struct platform_driver gcc_ipq4019_driver = {
-- 
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