rtc: pxa: fix null pointer dereference

With the latest stable kernel versions the rtc on the PXA based Zaurus does not work, when booting I see the following kernel messages:

pxa-rtc pxa-rtc: failed to find rtc clock source pxa-rtc pxa-rtc: Unable to init SA1100 RTC sub-device
pxa-rtc: probe of pxa-rtc failed with error -2
hctosys: unable to open rtc device (rtc0)

I think this is because commit f2997775b111 ("rtc: sa1100: fix possible race condition") moved the allocation of the rtc_device struct out of sa1100_rtc_init and into sa1100_rtc_probe. This means that pxa_rtc_probe also needs to do allocation for the rtc_device struct, otherwise sa1100_rtc_init will try to dereference a null pointer. This patch adds that allocation by copying how sa1100_rtc_probe in drivers/rtc/rtc-sa1100.c does it; after the IRQs are set up a managed rtc_device is allocated.

I've tested this patch with qemu-system-arm -machine akita and with a real Zaurus SL-C1000 applied to 4.19, 5.4, and 5.10.

---
 drivers/rtc/rtc-pxa.c | 4 ++++
 1 file changed, 4 insertions(+)

index d2f1d8f754bf..cf8119b6d320 100644
@@ -330,6 +330,10 @@ static int __init pxa_rtc_probe(struct platform_device *pdev)
 	if (sa1100_rtc->irq_alarm < 0)
 		return -ENXIO;
 
+	sa1100_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(sa1100_rtc->rtc))
+		return PTR_ERR(sa1100_rtc->rtc);
+
 	pxa_rtc->base = devm_ioremap(dev, pxa_rtc->ress->start,
 				resource_size(pxa_rtc->ress));
 	if (!pxa_rtc->base) {

2.34.1

Applied, thanks!

[1/1] rtc: pxa: fix null pointer dereference

      commit: 34127b3632b21e5c391756e724b1198eb9917981

Best regards,

Alexandre Belloni <[email protected]>