i2c: riic: Add Runtime PM support

- Replace explicit clock handling by Runtime PM calls,
  - Streamline Runtime PM handling in error paths,
  - Enable Runtime PM in .probe(),
  - Disable Runtime PM in .remove(),
  - Make sure the device is runtime-resumed when disabling interrupts in
    .remove().
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Chris Brandt <chris.brandt@renesas.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-riic.c

@@ -43,6 +43,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 
 #define RIIC_ICCR1	0x00
 #define RIIC_ICCR2	0x04
@@ -112,12 +113,10 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 {
 	struct riic_dev *riic = i2c_get_adapdata(adap);
 	unsigned long time_left;
-	int i, ret;
+	int i;
 	u8 start_bit;
 
-	ret = clk_prepare_enable(riic->clk);
-	if (ret)
-		return ret;
+	pm_runtime_get_sync(adap->dev.parent);
 
 	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
 		riic->err = -EBUSY;
@@ -150,7 +149,7 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	}
 
  out:
-	clk_disable_unprepare(riic->clk);
+	pm_runtime_put(adap->dev.parent);
 
 	return riic->err ?: num;
 }
@@ -281,20 +280,18 @@ static const struct i2c_algorithm riic_algo = {
 
 static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
 {
-	int ret;
+	int ret = 0;
 	unsigned long rate;
 	int total_ticks, cks, brl, brh;
 
-	ret = clk_prepare_enable(riic->clk);
-	if (ret)
-		return ret;
+	pm_runtime_get_sync(riic->adapter.dev.parent);
 
 	if (t->bus_freq_hz > 400000) {
 		dev_err(&riic->adapter.dev,
 			"unsupported bus speed (%dHz). 400000 max\n",
 			t->bus_freq_hz);
-		clk_disable_unprepare(riic->clk);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	rate = clk_get_rate(riic->clk);
@@ -332,8 +329,8 @@ static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
 	if (brl > (0x1F + 3)) {
 		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
 			(unsigned long)t->bus_freq_hz);
-		clk_disable_unprepare(riic->clk);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	brh = total_ticks - brl;
@@ -378,9 +375,9 @@ static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
 
 	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
 
-	clk_disable_unprepare(riic->clk);
-
-	return 0;
+out:
+	pm_runtime_put(riic->adapter.dev.parent);
+	return ret;
 }
 
 static struct riic_irq_desc riic_irqs[] = {
@@ -439,28 +436,36 @@ static int riic_i2c_probe(struct platform_device *pdev)
 
 	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
 
+	pm_runtime_enable(&pdev->dev);
+
 	ret = riic_init_hw(riic, &i2c_t);
 	if (ret)
-		return ret;
-
+		goto out;
 
 	ret = i2c_add_adapter(adap);
 	if (ret)
-		return ret;
+		goto out;
 
 	platform_set_drvdata(pdev, riic);
 
 	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
 		 i2c_t.bus_freq_hz);
 	return 0;
+
+out:
+	pm_runtime_disable(&pdev->dev);
+	return ret;
 }
 
 static int riic_i2c_remove(struct platform_device *pdev)
 {
 	struct riic_dev *riic = platform_get_drvdata(pdev);
 
+	pm_runtime_get_sync(&pdev->dev);
 	writeb(0, riic->base + RIIC_ICIER);
+	pm_runtime_put(&pdev->dev);
 	i2c_del_adapter(&riic->adapter);
+	pm_runtime_disable(&pdev->dev);
 
 	return 0;
 }