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From:   Sowjanya Komatineni <skomatineni@nvidia.com>
To:     <thierry.reding@gmail.com>, <jonathanh@nvidia.com>,
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Subject: [PATCH V6 12/21] cpufreq: tegra124: Add suspend and resume support
Date:   Sun, 21 Jul 2019 12:40:51 -0700
Message-ID: <1563738060-30213-13-git-send-email-skomatineni@nvidia.com>
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This patch adds suspend and resume pm ops for cpufreq driver.

PLLP is the safe clock source for CPU during system suspend and
resume as PLLP rate is below the CPU Fmax at Vmin.

CPUFreq driver suspend switches the CPU clock source to PLLP and
disables the DFLL clock.

During system resume, warmboot code powers up the CPU with PLLP
clock source. So CPUFreq driver resume enabled DFLL clock and
switches CPU back to DFLL clock source.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
---
 drivers/cpufreq/tegra124-cpufreq.c | 46 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/drivers/cpufreq/tegra124-cpufreq.c b/drivers/cpufreq/tegra124-cpufreq.c
index 4f0c637b3b49..4eff63379b0f 100644
--- a/drivers/cpufreq/tegra124-cpufreq.c
+++ b/drivers/cpufreq/tegra124-cpufreq.c
@@ -6,6 +6,7 @@
 #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
 
 #include <linux/clk.h>
+#include <linux/cpufreq.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -128,8 +129,53 @@ static int tegra124_cpufreq_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static int tegra124_cpufreq_suspend(struct device *dev)
+{
+	struct tegra124_cpufreq_priv *priv = dev_get_drvdata(dev);
+
+	/*
+	 * PLLP rate 408Mhz is below the CPU Fmax at Vmin and is safe to
+	 * use during suspend and resume. So, switch the CPU clock source
+	 * to PLLP and disable DFLL.
+	 */
+	clk_set_parent(priv->cpu_clk, priv->pllp_clk);
+
+	/* disable DFLL clock */
+	clk_disable_unprepare(priv->dfll_clk);
+
+	return 0;
+}
+
+static int tegra124_cpufreq_resume(struct device *dev)
+{
+	struct tegra124_cpufreq_priv *priv = dev_get_drvdata(dev);
+	int ret = 0;
+
+	/*
+	 * Warmboot code powers up the CPU with PLLP clock source.
+	 * Enable DFLL clock and switch CPU clock source back to DFLL.
+	 */
+	ret = clk_prepare_enable(priv->dfll_clk);
+	if (ret) {
+		dev_warn(dev, "failed to enable DFLL clock for CPU\n");
+		clk_set_parent(priv->cpu_clk, priv->pllp_clk);
+		disable_cpufreq();
+		return ret;
+	}
+
+	clk_set_parent(priv->cpu_clk, priv->dfll_clk);
+
+	return ret;
+}
+
+static const struct dev_pm_ops tegra124_cpufreq_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(tegra124_cpufreq_suspend,
+				tegra124_cpufreq_resume)
+};
+
 static struct platform_driver tegra124_cpufreq_platdrv = {
 	.driver.name	= "cpufreq-tegra124",
+	.driver.pm	= &tegra124_cpufreq_pm_ops,
 	.probe		= tegra124_cpufreq_probe,
 };
 
-- 
2.7.4