clk: samsung: exynos-audss: Add support for runtime PM

This patch adds support for runtime PM to Exynos Audio SubSystem driver to
enable full support for audio power domain on Exynos5 SoCs. The main change
is moving register saving and restoring code from system sleep PM ops to
runtime PM ops and implementing system sleep PM ops with generic
pm_runtime_force_suspend/resume helpers. Runtime PM of the Exynos AudSS
device is managed from clock core depending on the preparation status
of the provided clocks.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1503302703-13801-6-git-send-email-m.szyprowski@samsung.com

Documentation/devicetree/bindings/clock/clk-exynos-audss.txt

@@ -33,6 +33,12 @@ Required Properties:
 - clock-names: Aliases for the above clocks. They should be "pll_ref",
   "pll_in", "cdclk", "sclk_audio", and "sclk_pcm_in" respectively.
 
+Optional Properties:
+
+  - power-domains: a phandle to respective power domain node as described by
+    generic PM domain bindings (see power/power_domain.txt for more
+    information).
+
 The following is the list of clocks generated by the controller. Each clock is
 assigned an identifier and client nodes use this identifier to specify the
 clock which they consume. Some of the clocks are available only on a particular

drivers/clk/samsung/clk-exynos-audss.c

@@ -18,6 +18,7 @@
 #include <linux/syscore_ops.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 
 #include <dt-bindings/clock/exynos-audss-clk.h>
 
@@ -36,14 +37,13 @@ static struct clk *epll;
 #define ASS_CLK_DIV 0x4
 #define ASS_CLK_GATE 0x8
 
-#ifdef CONFIG_PM_SLEEP
 static unsigned long reg_save[][2] = {
 	{ ASS_CLK_SRC,  0 },
 	{ ASS_CLK_DIV,  0 },
 	{ ASS_CLK_GATE, 0 },
 };
 
-static int exynos_audss_clk_suspend(struct device *dev)
+static int __maybe_unused exynos_audss_clk_suspend(struct device *dev)
 {
 	int i;
 
@@ -53,7 +53,7 @@ static int exynos_audss_clk_suspend(struct device *dev)
 	return 0;
 }
 
-static int exynos_audss_clk_resume(struct device *dev)
+static int __maybe_unused exynos_audss_clk_resume(struct device *dev)
 {
 	int i;
 
@@ -62,7 +62,6 @@ static int exynos_audss_clk_resume(struct device *dev)
 
 	return 0;
 }
-#endif /* CONFIG_PM_SLEEP */
 
 struct exynos_audss_clk_drvdata {
 	unsigned int has_adma_clk:1;
@@ -179,7 +178,18 @@ static int exynos_audss_clk_probe(struct platform_device *pdev)
 			}
 		}
 	}
-	clk_table[EXYNOS_MOUT_AUDSS] = clk_hw_register_mux(NULL, "mout_audss",
+
+	/*
+	 * Enable runtime PM here to allow the clock core using runtime PM
+	 * for the registered clocks. Additionally, we increase the runtime
+	 * PM usage count before registering the clocks, to prevent the
+	 * clock core from runtime suspending the device.
+	 */
+	pm_runtime_get_noresume(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+
+	clk_table[EXYNOS_MOUT_AUDSS] = clk_hw_register_mux(dev, "mout_audss",
 				mout_audss_p, ARRAY_SIZE(mout_audss_p),
 				CLK_SET_RATE_NO_REPARENT,
 				reg_base + ASS_CLK_SRC, 0, 1, 0, &lock);
@@ -190,48 +200,48 @@ static int exynos_audss_clk_probe(struct platform_device *pdev)
 		mout_i2s_p[1] = __clk_get_name(cdclk);
 	if (!IS_ERR(sclk_audio))
 		mout_i2s_p[2] = __clk_get_name(sclk_audio);
-	clk_table[EXYNOS_MOUT_I2S] = clk_hw_register_mux(NULL, "mout_i2s",
+	clk_table[EXYNOS_MOUT_I2S] = clk_hw_register_mux(dev, "mout_i2s",
 				mout_i2s_p, ARRAY_SIZE(mout_i2s_p),
 				CLK_SET_RATE_NO_REPARENT,
 				reg_base + ASS_CLK_SRC, 2, 2, 0, &lock);
 
-	clk_table[EXYNOS_DOUT_SRP] = clk_hw_register_divider(NULL, "dout_srp",
+	clk_table[EXYNOS_DOUT_SRP] = clk_hw_register_divider(dev, "dout_srp",
 				"mout_audss", 0, reg_base + ASS_CLK_DIV, 0, 4,
 				0, &lock);
 
-	clk_table[EXYNOS_DOUT_AUD_BUS] = clk_hw_register_divider(NULL,
+	clk_table[EXYNOS_DOUT_AUD_BUS] = clk_hw_register_divider(dev,
 				"dout_aud_bus", "dout_srp", 0,
 				reg_base + ASS_CLK_DIV, 4, 4, 0, &lock);
 
-	clk_table[EXYNOS_DOUT_I2S] = clk_hw_register_divider(NULL, "dout_i2s",
+	clk_table[EXYNOS_DOUT_I2S] = clk_hw_register_divider(dev, "dout_i2s",
 				"mout_i2s", 0, reg_base + ASS_CLK_DIV, 8, 4, 0,
 				&lock);
 
-	clk_table[EXYNOS_SRP_CLK] = clk_hw_register_gate(NULL, "srp_clk",
+	clk_table[EXYNOS_SRP_CLK] = clk_hw_register_gate(dev, "srp_clk",
 				"dout_srp", CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 0, 0, &lock);
 
-	clk_table[EXYNOS_I2S_BUS] = clk_hw_register_gate(NULL, "i2s_bus",
+	clk_table[EXYNOS_I2S_BUS] = clk_hw_register_gate(dev, "i2s_bus",
 				"dout_aud_bus", CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 2, 0, &lock);
 
-	clk_table[EXYNOS_SCLK_I2S] = clk_hw_register_gate(NULL, "sclk_i2s",
+	clk_table[EXYNOS_SCLK_I2S] = clk_hw_register_gate(dev, "sclk_i2s",
 				"dout_i2s", CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 3, 0, &lock);
 
-	clk_table[EXYNOS_PCM_BUS] = clk_hw_register_gate(NULL, "pcm_bus",
+	clk_table[EXYNOS_PCM_BUS] = clk_hw_register_gate(dev, "pcm_bus",
 				 "sclk_pcm", CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 4, 0, &lock);
 
 	sclk_pcm_in = devm_clk_get(dev, "sclk_pcm_in");
 	if (!IS_ERR(sclk_pcm_in))
 		sclk_pcm_p = __clk_get_name(sclk_pcm_in);
-	clk_table[EXYNOS_SCLK_PCM] = clk_hw_register_gate(NULL, "sclk_pcm",
+	clk_table[EXYNOS_SCLK_PCM] = clk_hw_register_gate(dev, "sclk_pcm",
 				sclk_pcm_p, CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 5, 0, &lock);
 
 	if (variant->has_adma_clk) {
-		clk_table[EXYNOS_ADMA] = clk_hw_register_gate(NULL, "adma",
+		clk_table[EXYNOS_ADMA] = clk_hw_register_gate(dev, "adma",
 				"dout_srp", CLK_SET_RATE_PARENT,
 				reg_base + ASS_CLK_GATE, 9, 0, &lock);
 	}
@@ -251,10 +261,14 @@ static int exynos_audss_clk_probe(struct platform_device *pdev)
 		goto unregister;
 	}
 
+	pm_runtime_put_sync(dev);
+
 	return 0;
 
 unregister:
 	exynos_audss_clk_teardown();
+	pm_runtime_put_sync(dev);
+	pm_runtime_disable(dev);
 
 	if (!IS_ERR(epll))
 		clk_disable_unprepare(epll);
@@ -267,6 +281,7 @@ static int exynos_audss_clk_remove(struct platform_device *pdev)
 	of_clk_del_provider(pdev->dev.of_node);
 
 	exynos_audss_clk_teardown();
+	pm_runtime_disable(&pdev->dev);
 
 	if (!IS_ERR(epll))
 		clk_disable_unprepare(epll);
@@ -275,8 +290,10 @@ static int exynos_audss_clk_remove(struct platform_device *pdev)
 }
 
 static const struct dev_pm_ops exynos_audss_clk_pm_ops = {
-	SET_LATE_SYSTEM_SLEEP_PM_OPS(exynos_audss_clk_suspend,
-				     exynos_audss_clk_resume)
+	SET_RUNTIME_PM_OPS(exynos_audss_clk_suspend, exynos_audss_clk_resume,
+			   NULL)
+	SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				     pm_runtime_force_resume)
 };
 
 static struct platform_driver exynos_audss_clk_driver = {