[PATCH] rtc: pcf2127: arm the alarm IRQ as a wake IRQ

[Aristo Chen <aristo.chen@canonical.com>]

When an alarm IRQ is available, the driver calls device_init_wakeup(),
so the RTC shows up as wakeup capable and enabled, but it never marks
the IRQ itself as a wakeup interrupt. The PM core therefore disables
the IRQ for the whole system suspend, and the alarm cannot wake the
system: "rtcwake -m mem" on this RTC only resumes once another wakeup
source fires.

On the i.MX93 11x11 FRDM board the PCF2131 alarm is routed through a
PCAL6524 GPIO expander. Without a wakeup request on the expander pin,
the expander's own interrupt is not armed for wakeup either, so the
alarm never reaches the CPU. The BBNSM RTC on the same board uses
devm_pm_set_wake_irq() and wakes the system as expected.

Register the alarm IRQ with devm_pm_set_wake_irq() so that the PM core
arms it whenever the device may wake the system. A failure is not
fatal: the RTC keeps working, only wakeup from it is unavailable.

Fixes: 8a914bac44be ("rtc: pcf2127: add alarm support")
Assisted-by: LLM
Signed-off-by: Aristo Chen <aristo.chen@canonical.com>
---
Tested on an i.MX93 FRDM board, where the PCF2131 INTA reaches the SoC
through a PCAL6524 GPIO expander. The board ran an Ubuntu 6.8 kernel
with devm_pm_set_wake_irq() (fd8318a32573) and tcpci wakeup support
(a5d2edb2c9fa) backported. With this patch, the PCF2131 alarm wakes the
board from suspend-to-RAM and from s2idle, also after unbinding and
rebinding the driver. Without it, the alarm doesn't wake the board from
suspend-to-RAM. Compile-tested on rtc-next (arm64 defconfig plus
RTC_DRV_PCF2127, W=1).

 drivers/rtc/rtc-pcf2127.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
index ff2023908..51d8aebf3 100644
--- a/drivers/rtc/rtc-pcf2127.c
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -27,6 +27,7 @@
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_device.h>
+#include <linux/pm_wakeirq.h>
 #include <linux/regmap.h>
 #include <linux/watchdog.h>
 
@@ -1251,6 +1252,12 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
 	if (alarm_irq > 0 || device_property_read_bool(dev, "wakeup-source")) {
 		device_init_wakeup(dev, true);
 		set_bit(RTC_FEATURE_ALARM, pcf2127->rtc->features);
+
+		if (alarm_irq > 0) {
+			ret = devm_pm_set_wake_irq(dev, alarm_irq);
+			if (ret)
+				dev_warn(dev, "failed to set wake IRQ: %d\n", ret);
+		}
 	}
 
 	if (pcf2127->cfg->has_int_a_b) {
-- 
2.43.0