drivers/rtc/rtc-s5m.c: re-add support for devices without irq specified

The rtc-s5m driver used to support devices without irq specified in the
past.  Re-add this support.

The patch fixes boot for Insignal's Exynos4412 based Origen board.

Error messages before the patch:

  ...
  Unable to handle kernel NULL pointer dereference at virtual address 00000094
  pgd = c0004000
  [00000094] *pgd=00000000
  Internal error: Oops: 5 [#1] PREEMPT SMP ARM
  Modules linked in:
  CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.16.0-next-20140804-00008-ga59480f-dirty #701
  task: ea80f000 ti: ea882000 task.ti: ea882000
  PC is at regmap_irq_get_virq+0x0/0x28
  LR is at s5m_rtc_probe+0xdc/0x310
  pc : [<c02574fc>]    lr : [<c02de75c>]    psr: 80000153
  sp : ea883e48  ip : 00000000  fp : 00000000
  r10: 0000000c  r9 : c05de7ac  r8 : eaabc600
  r7 : eaa6b4d0  r6 : c0439e8c  r5 : eaabc610  r4 : eab30e50
  r3 : 00000000  r2 : 00000000  r1 : 0000000c  r0 : 00000000
  Flags: Nzcv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
  Control: 10c5387d  Table: 4000404a  DAC: 00000015
  Process swapper/0 (pid: 1, stack limit = 0xea882240)
  Backtrace:
    regmap_irq_get_virq
    s5m_rtc_probe
    platform_drv_probe
    driver_probe_device
    __driver_attach
    bus_for_each_dev
    bus_add_driver
    driver_register
    do_one_initcall
    kernel_init_freeable
    kernel_init
  ---[ end trace a954d7f019122700 ]---
  Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
  ...

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-s5m.c

@@ -717,12 +717,14 @@ static int s5m_rtc_probe(struct platform_device *pdev)
 	info->device_type = s5m87xx->device_type;
 	info->wtsr_smpl = s5m87xx->wtsr_smpl;
 
-	info->irq = regmap_irq_get_virq(s5m87xx->irq_data, alarm_irq);
-	if (info->irq <= 0) {
-		ret = -EINVAL;
-		dev_err(&pdev->dev, "Failed to get virtual IRQ %d\n",
+	if (s5m87xx->irq_data) {
+		info->irq = regmap_irq_get_virq(s5m87xx->irq_data, alarm_irq);
+		if (info->irq <= 0) {
+			ret = -EINVAL;
+			dev_err(&pdev->dev, "Failed to get virtual IRQ %d\n",
 				alarm_irq);
-		goto err;
+			goto err;
+		}
 	}
 
 	platform_set_drvdata(pdev, info);
@@ -744,6 +746,11 @@ static int s5m_rtc_probe(struct platform_device *pdev)
 		goto err;
 	}
 
+	if (!info->irq) {
+		dev_info(&pdev->dev, "Alarm IRQ not available\n");
+		return 0;
+	}
+
 	ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL,
 					s5m_rtc_alarm_irq, 0, "rtc-alarm0",
 					info);
@@ -802,7 +809,7 @@ static int s5m_rtc_resume(struct device *dev)
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
 	int ret = 0;
 
-	if (device_may_wakeup(dev))
+	if (info->irq && device_may_wakeup(dev))
 		ret = disable_irq_wake(info->irq);
 
 	return ret;
@@ -813,7 +820,7 @@ static int s5m_rtc_suspend(struct device *dev)
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
 	int ret = 0;
 
-	if (device_may_wakeup(dev))
+	if (info->irq && device_may_wakeup(dev))
 		ret = enable_irq_wake(info->irq);
 
 	return ret;