hwrng: xgene - Simplify using devm_clk_get_optional_enabled()

Instead of ignoring errors returned by devm_clk_get() and manually
enabling the clk for the whole lifetime of the bound device, use
devm_clk_get_optional_enabled(). This is simpler and also more correct
as it doesn't ignore errors. This is also more correct because now the
call to clk_disable_unprepare() can be dropped from xgene_rng_remove()
which happened while the hwrn device was still registered. With the devm
callback disabling the clk happens correctly only after
devm_hwrng_register() is undone.

As a result struct xgene_rng_dev::clk is only used in xgene_rng_probe, and
so the struct member can be replaced by a local variable.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/xgene-rng.c

@@ -84,7 +84,6 @@ struct xgene_rng_dev {
 	unsigned long failure_ts;/* First failure timestamp */
 	struct timer_list failure_timer;
 	struct device *dev;
-	struct clk *clk;
 };
 
 static void xgene_rng_expired_timer(struct timer_list *t)
@@ -314,6 +313,7 @@ static struct hwrng xgene_rng_func = {
 static int xgene_rng_probe(struct platform_device *pdev)
 {
 	struct xgene_rng_dev *ctx;
+	struct clk *clk;
 	int rc = 0;
 
 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
@@ -341,45 +341,30 @@ static int xgene_rng_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, rc, "Could not request RNG alarm IRQ\n");
 
 	/* Enable IP clock */
-	ctx->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(ctx->clk)) {
-		dev_warn(&pdev->dev, "Couldn't get the clock for RNG\n");
-	} else {
-		rc = clk_prepare_enable(ctx->clk);
-		if (rc)
-			return dev_err_probe(&pdev->dev, rc,
-					     "clock prepare enable failed for RNG");
-	}
+	clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "Couldn't get the clock for RNG\n");
 
 	xgene_rng_func.priv = (unsigned long) ctx;
 
 	rc = devm_hwrng_register(&pdev->dev, &xgene_rng_func);
-	if (rc) {
-		if (!IS_ERR(ctx->clk))
-			clk_disable_unprepare(ctx->clk);
+	if (rc)
 		return dev_err_probe(&pdev->dev, rc, "RNG registering failed\n");
-	}
 
 	rc = device_init_wakeup(&pdev->dev, 1);
-	if (rc) {
-		if (!IS_ERR(ctx->clk))
-			clk_disable_unprepare(ctx->clk);
+	if (rc)
 		return dev_err_probe(&pdev->dev, rc, "RNG device_init_wakeup failed\n");
-	}
 
 	return 0;
 }
 
 static int xgene_rng_remove(struct platform_device *pdev)
 {
-	struct xgene_rng_dev *ctx = platform_get_drvdata(pdev);
 	int rc;
 
 	rc = device_init_wakeup(&pdev->dev, 0);
 	if (rc)
 		dev_err(&pdev->dev, "RNG init wakeup failed error %d\n", rc);
-	if (!IS_ERR(ctx->clk))
-		clk_disable_unprepare(ctx->clk);
 
 	return rc;
 }