i2c: mv64xxx: Add runtime PM support

To save power, gate the clock when the bus is inactive, during system
sleep, and during shutdown. On some platforms, specifically Allwinner
A13/A20, gating the clock implicitly resets the module as well. Since
the module already needs to be reset after some suspend/resume cycles,
it is simple enough to reset it during every runtime suspend/resume.

Because the bus may be used by wakeup source IRQ threads, it needs to
be functional as soon as IRQs are enabled. Thus, its system PM hooks
need to run in the noirq phase.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Tested-by: Ondrej Jirman <megous@megous.com>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-mv64xxx.c

@@ -18,6 +18,7 @@
 #include <linux/mv643xx_i2c.h>
 #include <linux/platform_device.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/pm_runtime.h>
 #include <linux/reset.h>
 #include <linux/io.h>
 #include <linux/of.h>
@@ -717,6 +718,10 @@ mv64xxx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	struct mv64xxx_i2c_data *drv_data = i2c_get_adapdata(adap);
 	int rc, ret = num;
 
+	rc = pm_runtime_resume_and_get(&adap->dev);
+	if (rc)
+		return rc;
+
 	BUG_ON(drv_data->msgs != NULL);
 	drv_data->msgs = msgs;
 	drv_data->num_msgs = num;
@@ -732,6 +737,9 @@ mv64xxx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	drv_data->num_msgs = 0;
 	drv_data->msgs = NULL;
 
+	pm_runtime_mark_last_busy(&adap->dev);
+	pm_runtime_put_autosuspend(&adap->dev);
+
 	return ret;
 }
 
@@ -828,7 +836,6 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
 		rc = PTR_ERR(drv_data->rstc);
 		goto out;
 	}
-	reset_control_deassert(drv_data->rstc);
 
 	/* Its not yet defined how timeouts will be specified in device tree.
 	 * So hard code the value to 1 second.
@@ -893,6 +900,32 @@ static int mv64xxx_i2c_init_recovery_info(struct mv64xxx_i2c_data *drv_data,
 	return 0;
 }
 
+static int
+mv64xxx_i2c_runtime_suspend(struct device *dev)
+{
+	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
+
+	reset_control_assert(drv_data->rstc);
+	clk_disable_unprepare(drv_data->reg_clk);
+	clk_disable_unprepare(drv_data->clk);
+
+	return 0;
+}
+
+static int
+mv64xxx_i2c_runtime_resume(struct device *dev)
+{
+	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
+
+	clk_prepare_enable(drv_data->clk);
+	clk_prepare_enable(drv_data->reg_clk);
+	reset_control_reset(drv_data->rstc);
+
+	mv64xxx_i2c_hw_init(drv_data);
+
+	return 0;
+}
+
 static int
 mv64xxx_i2c_probe(struct platform_device *pd)
 {
@@ -920,18 +953,22 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 
 	/* Not all platforms have clocks */
 	drv_data->clk = devm_clk_get(&pd->dev, NULL);
+	if (IS_ERR(drv_data->clk)) {
 		if (PTR_ERR(drv_data->clk) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
-	if (!IS_ERR(drv_data->clk))
-		clk_prepare_enable(drv_data->clk);
+		drv_data->clk = NULL;
+	}
 
 	drv_data->reg_clk = devm_clk_get(&pd->dev, "reg");
+	if (IS_ERR(drv_data->reg_clk)) {
 		if (PTR_ERR(drv_data->reg_clk) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
-	if (!IS_ERR(drv_data->reg_clk))
-		clk_prepare_enable(drv_data->reg_clk);
+		drv_data->reg_clk = NULL;
+	}
 
 	drv_data->irq = platform_get_irq(pd, 0);
+	if (drv_data->irq < 0)
+		return drv_data->irq;
 
 	if (pdata) {
 		drv_data->freq_m = pdata->freq_m;
@@ -942,16 +979,12 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	} else if (pd->dev.of_node) {
 		rc = mv64xxx_of_config(drv_data, &pd->dev);
 		if (rc)
-			goto exit_clk;
-	}
-	if (drv_data->irq < 0) {
-		rc = drv_data->irq;
-		goto exit_reset;
+			return rc;
 	}
 
 	rc = mv64xxx_i2c_init_recovery_info(drv_data, &pd->dev);
 	if (rc == -EPROBE_DEFER)
-		goto exit_reset;
+		return rc;
 
 	drv_data->adapter.dev.parent = &pd->dev;
 	drv_data->adapter.algo = &mv64xxx_i2c_algo;
@@ -962,7 +995,14 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	platform_set_drvdata(pd, drv_data);
 	i2c_set_adapdata(&drv_data->adapter, drv_data);
 
-	mv64xxx_i2c_hw_init(drv_data);
+	pm_runtime_set_autosuspend_delay(&pd->dev, MSEC_PER_SEC);
+	pm_runtime_use_autosuspend(&pd->dev);
+	pm_runtime_enable(&pd->dev);
+	if (!pm_runtime_enabled(&pd->dev)) {
+		rc = mv64xxx_i2c_runtime_resume(&pd->dev);
+		if (rc)
+			goto exit_disable_pm;
+	}
 
 	rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
 			 MV64XXX_I2C_CTLR_NAME, drv_data);
@@ -970,7 +1010,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 		dev_err(&drv_data->adapter.dev,
 			"mv64xxx: Can't register intr handler irq%d: %d\n",
 			drv_data->irq, rc);
-		goto exit_reset;
+		goto exit_disable_pm;
 	} else if ((rc = i2c_add_numbered_adapter(&drv_data->adapter)) != 0) {
 		dev_err(&drv_data->adapter.dev,
 			"mv64xxx: Can't add i2c adapter, rc: %d\n", -rc);
@@ -981,54 +1021,50 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 
 exit_free_irq:
 	free_irq(drv_data->irq, drv_data);
-exit_reset:
-	reset_control_assert(drv_data->rstc);
-exit_clk:
-	clk_disable_unprepare(drv_data->reg_clk);
-	clk_disable_unprepare(drv_data->clk);
+exit_disable_pm:
+	pm_runtime_disable(&pd->dev);
+	if (!pm_runtime_status_suspended(&pd->dev))
+		mv64xxx_i2c_runtime_suspend(&pd->dev);
 
 	return rc;
 }
 
 static int
-mv64xxx_i2c_remove(struct platform_device *dev)
+mv64xxx_i2c_remove(struct platform_device *pd)
 {
-	struct mv64xxx_i2c_data		*drv_data = platform_get_drvdata(dev);
+	struct mv64xxx_i2c_data		*drv_data = platform_get_drvdata(pd);
 
 	i2c_del_adapter(&drv_data->adapter);
 	free_irq(drv_data->irq, drv_data);
-	reset_control_assert(drv_data->rstc);
-	clk_disable_unprepare(drv_data->reg_clk);
-	clk_disable_unprepare(drv_data->clk);
+	pm_runtime_disable(&pd->dev);
+	if (!pm_runtime_status_suspended(&pd->dev))
+		mv64xxx_i2c_runtime_suspend(&pd->dev);
 
 	return 0;
 }
 
-#ifdef CONFIG_PM
-static int mv64xxx_i2c_resume(struct device *dev)
+static void
+mv64xxx_i2c_shutdown(struct platform_device *pd)
 {
-	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
-
-	mv64xxx_i2c_hw_init(drv_data);
-
-	return 0;
+	pm_runtime_disable(&pd->dev);
+	if (!pm_runtime_status_suspended(&pd->dev))
+		mv64xxx_i2c_runtime_suspend(&pd->dev);
 }
 
-static const struct dev_pm_ops mv64xxx_i2c_pm = {
-	.resume = mv64xxx_i2c_resume,
+static const struct dev_pm_ops mv64xxx_i2c_pm_ops = {
+	SET_RUNTIME_PM_OPS(mv64xxx_i2c_runtime_suspend,
+			   mv64xxx_i2c_runtime_resume, NULL)
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				      pm_runtime_force_resume)
 };
 
-#define mv64xxx_i2c_pm_ops (&mv64xxx_i2c_pm)
-#else
-#define mv64xxx_i2c_pm_ops NULL
-#endif
-
 static struct platform_driver mv64xxx_i2c_driver = {
 	.probe	= mv64xxx_i2c_probe,
 	.remove	= mv64xxx_i2c_remove,
+	.shutdown = mv64xxx_i2c_shutdown,
 	.driver	= {
 		.name	= MV64XXX_I2C_CTLR_NAME,
-		.pm     = mv64xxx_i2c_pm_ops,
+		.pm     = &mv64xxx_i2c_pm_ops,
 		.of_match_table = mv64xxx_i2c_of_match_table,
 	},
 };