rtc: ds1511: let the core know when alarm are not supported

Instead of failing function calls, let the core know alarms are not
supported so it can fail early and avoid unnecessary calls.

Link: https://lore.kernel.org/r/20240227230431.1837717-8-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-ds1511.c

@@ -188,9 +188,6 @@ static int ds1511_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
 	unsigned long flags;
 
-	if (pdata->irq <= 0)
-		return -EINVAL;
-
 	pdata->alrm_mday = alrm->time.tm_mday;
 	pdata->alrm_hour = alrm->time.tm_hour;
 	pdata->alrm_min = alrm->time.tm_min;
@@ -219,9 +216,6 @@ static int ds1511_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
 
-	if (pdata->irq <= 0)
-		return -EINVAL;
-
 	alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
 	alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
 	alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
@@ -253,9 +247,6 @@ static int ds1511_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
 	unsigned long flags;
 
-	if (pdata->irq <= 0)
-		return -EINVAL;
-
 	spin_lock_irqsave(&pdata->lock, flags);
 	ds1511_rtc_alarm_enable(enabled);
 	spin_unlock_irqrestore(&pdata->lock, flags);
@@ -349,12 +340,6 @@ static int ds1511_rtc_probe(struct platform_device *pdev)
 
 	pdata->rtc->ops = &ds1511_rtc_ops;
 
-	ret = devm_rtc_register_device(pdata->rtc);
-	if (ret)
-		return ret;
-
-	devm_rtc_nvmem_register(pdata->rtc, &ds1511_nvmem_cfg);
-
 	/*
 	 * if the platform has an interrupt in mind for this device,
 	 * then by all means, set it
@@ -369,6 +354,15 @@ static int ds1511_rtc_probe(struct platform_device *pdev)
 		}
 	}
 
+	if (pdata->irq == 0)
+		clear_bit(RTC_FEATURE_ALARM, pdata->rtc->features);
+
+	ret = devm_rtc_register_device(pdata->rtc);
+	if (ret)
+		return ret;
+
+	devm_rtc_nvmem_register(pdata->rtc, &ds1511_nvmem_cfg);
+
 	return 0;
 }