drivers: bus: simple-pm-bus: Use clocks

Simple Power-Managed bus controller may need functional clock(s)
to be enabled before child devices connected to the bus can be
accessed.  Get the clock(s) as a bulk and enable/disable the
clock(s) when the bus is being power managed.

One example is that Freescale i.MX8qxp pixel link MSI bus controller
needs MSI clock and AHB clock to be enabled before accessing child
devices.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Tested-by: Maxim Kochetkov <fido_max@inbox.ru>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20221226031417.1056745-1-victor.liu@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/bus/simple-pm-bus.c

@@ -8,17 +8,24 @@
  * for more details.
  */
 
+#include <linux/clk.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 
+struct simple_pm_bus {
+	struct clk_bulk_data *clks;
+	int num_clks;
+};
+
 static int simple_pm_bus_probe(struct platform_device *pdev)
 {
 	const struct device *dev = &pdev->dev;
 	const struct of_dev_auxdata *lookup = dev_get_platdata(dev);
 	struct device_node *np = dev->of_node;
 	const struct of_device_id *match;
+	struct simple_pm_bus *bus;
 
 	/*
 	 * Allow user to use driver_override to bind this driver to a
@@ -44,6 +51,16 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
 			return -ENODEV;
 	}
 
+	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
+	if (!bus)
+		return -ENOMEM;
+
+	bus->num_clks = devm_clk_bulk_get_all(&pdev->dev, &bus->clks);
+	if (bus->num_clks < 0)
+		return dev_err_probe(&pdev->dev, bus->num_clks, "failed to get clocks\n");
+
+	dev_set_drvdata(&pdev->dev, bus);
+
 	dev_dbg(&pdev->dev, "%s\n", __func__);
 
 	pm_runtime_enable(&pdev->dev);
@@ -67,6 +84,34 @@ static int simple_pm_bus_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static int simple_pm_bus_runtime_suspend(struct device *dev)
+{
+	struct simple_pm_bus *bus = dev_get_drvdata(dev);
+
+	clk_bulk_disable_unprepare(bus->num_clks, bus->clks);
+
+	return 0;
+}
+
+static int simple_pm_bus_runtime_resume(struct device *dev)
+{
+	struct simple_pm_bus *bus = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_bulk_prepare_enable(bus->num_clks, bus->clks);
+	if (ret) {
+		dev_err(dev, "failed to enable clocks: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops simple_pm_bus_pm_ops = {
+	RUNTIME_PM_OPS(simple_pm_bus_runtime_suspend, simple_pm_bus_runtime_resume, NULL)
+	NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+};
+
 #define ONLY_BUS	((void *) 1) /* Match if the device is only a bus. */
 
 static const struct of_device_id simple_pm_bus_of_match[] = {
@@ -85,6 +130,7 @@ static struct platform_driver simple_pm_bus_driver = {
 	.driver = {
 		.name = "simple-pm-bus",
 		.of_match_table = simple_pm_bus_of_match,
+		.pm = pm_ptr(&simple_pm_bus_pm_ops),
 	},
 };