hwrng: imx-rngc - add runtime pm

Add runtime power management to the imx-rngc driver. Disable the
peripheral clock when the rngc is idle.

The callback functions from struct hwrng wake the rngc up when they're
called and set it to idle on exit. Helper functions which are invoked
from the callbacks assume that the rngc is active.

Device init and probe are done before runtime pm is enabled. The
peripheral clock will be handled manually during these steps. Do not use
devres any more to enable/disable the peripheral clock, this conflicts
with runtime pm.

Signed-off-by: Martin Kaiser <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/char/hw_random/imx-rngc.c

···
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/pm_runtime.h>
 #include <linux/interrupt.h>
 #include <linux/hw_random.h>
 #include <linux/completion.h>
···
 
 #define RNGC_SELFTEST_TIMEOUT 2500 /* us */
 #define RNGC_SEED_TIMEOUT      200 /* ms */
+#define RNGC_PM_TIMEOUT        500 /* ms */
 
 static bool self_test = true;
 module_param(self_test, bool, 0);
···
 {
 	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
 	unsigned int status;
-	int retval = 0;
+	int err, retval = 0;
+
+	err = pm_runtime_resume_and_get(rngc->dev);
+	if (err)
+		return err;
 
 	while (max >= sizeof(u32)) {
 		status = readl(rngc->base + RNGC_STATUS);
···
 			max -= sizeof(u32);
 		}
 	}
+	pm_runtime_mark_last_busy(rngc->dev);
+	pm_runtime_put(rngc->dev);
 
 	return retval ? retval : -EIO;
 }
···
 {
 	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
 	u32 cmd, ctrl;
-	int ret;
+	int ret, err;
+
+	err = pm_runtime_resume_and_get(rngc->dev);
+	if (err)
+		return err;
 
 	/* clear error */
 	cmd = readl(rngc->base + RNGC_COMMAND);
···
 		ret = wait_for_completion_timeout(&rngc->rng_op_done,
 						  msecs_to_jiffies(RNGC_SEED_TIMEOUT));
 		if (!ret) {
-			ret = -ETIMEDOUT;
-			goto err;
+			err = -ETIMEDOUT;
+			goto out;
 		}
 
 	} while (rngc->err_reg == RNGC_ERROR_STATUS_STAT_ERR);
 
 	if (rngc->err_reg) {
-		ret = -EIO;
-		goto err;
+		err = -EIO;
+		goto out;
 	}
 
 	/*
···
 	ctrl |= RNGC_CTRL_AUTO_SEED;
 	writel(ctrl, rngc->base + RNGC_CONTROL);
 
+out:
 	/*
 	 * if initialisation was successful, we keep the interrupt
 	 * unmasked until imx_rngc_cleanup is called
 	 * we mask the interrupt ourselves if we return an error
 	 */
-	return 0;
+	if (err)
+		imx_rngc_irq_mask_clear(rngc);
 
-err:
-	imx_rngc_irq_mask_clear(rngc);
-	return ret;
+	pm_runtime_put(rngc->dev);
+	return err;
 }
 
 static void imx_rngc_cleanup(struct hwrng *rng)
 {
 	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
+	int err;
 
-	imx_rngc_irq_mask_clear(rngc);
+	err = pm_runtime_resume_and_get(rngc->dev);
+	if (!err) {
+		imx_rngc_irq_mask_clear(rngc);
+		pm_runtime_put(rngc->dev);
+	}
 }
 
 static int __init imx_rngc_probe(struct platform_device *pdev)
···
 	if (IS_ERR(rngc->base))
 		return PTR_ERR(rngc->base);
 
-	rngc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	rngc->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(rngc->clk))
 		return dev_err_probe(&pdev->dev, PTR_ERR(rngc->clk), "Cannot get rng_clk\n");
 
···
 	if (irq < 0)
 		return irq;
 
+	clk_prepare_enable(rngc->clk);
+
 	ver_id = readl(rngc->base + RNGC_VER_ID);
 	rng_type = FIELD_GET(RNG_TYPE, ver_id);
 	/*
 	 * This driver supports only RNGC and RNGB. (There's a different
 	 * driver for RNGA.)
 	 */
-	if (rng_type != RNGC_TYPE_RNGC && rng_type != RNGC_TYPE_RNGB)
+	if (rng_type != RNGC_TYPE_RNGC && rng_type != RNGC_TYPE_RNGB) {
+		clk_disable_unprepare(rngc->clk);
 		return -ENODEV;
+	}
 
 	init_completion(&rngc->rng_op_done);
 
···
 
 	ret = devm_request_irq(&pdev->dev,
 			irq, imx_rngc_irq, 0, pdev->name, (void *)rngc);
-	if (ret)
+	if (ret) {
+		clk_disable_unprepare(rngc->clk);
 		return dev_err_probe(&pdev->dev, ret, "Can't get interrupt working.\n");
+	}
 
 	if (self_test) {
 		ret = imx_rngc_self_test(rngc);
-		if (ret)
+		if (ret) {
+			clk_disable_unprepare(rngc->clk);
 			return dev_err_probe(&pdev->dev, ret, "self test failed\n");
+		}
 	}
+
+	pm_runtime_set_autosuspend_delay(&pdev->dev, RNGC_PM_TIMEOUT);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+	devm_pm_runtime_enable(&pdev->dev);
 
 	ret = devm_hwrng_register(&pdev->dev, &rngc->rng);
 	if (ret)
···
 	return 0;
 }
 
-static DEFINE_SIMPLE_DEV_PM_OPS(imx_rngc_pm_ops, imx_rngc_suspend, imx_rngc_resume);
+static const struct dev_pm_ops imx_rngc_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+	RUNTIME_PM_OPS(imx_rngc_suspend, imx_rngc_resume, NULL)
+};
 
 static const struct of_device_id imx_rngc_dt_ids[] = {
 	{ .compatible = "fsl,imx25-rngb" },
···
 static struct platform_driver imx_rngc_driver = {
 	.driver = {
 		.name = KBUILD_MODNAME,
-		.pm = pm_sleep_ptr(&imx_rngc_pm_ops),
+		.pm = pm_ptr(&imx_rngc_pm_ops),
 		.of_match_table = imx_rngc_dt_ids,
 	},
 };