[PATCH] rtc: cros-ec: Limit RTC alarm range if needed

[Guenter Roeck <linux@roeck-us.net>]

RTC chips on some older Chromebooks can only handle alarms less than 24
hours in the future. Attempts to set an alarm beyond that range fails.
The most severe impact of this limitation is that suspend requests fail
if alarmtimer_suspend() tries to set an alarm for more than 24 hours
in the future.

Try to set the real-time alarm to just below 24 hours if setting it to
a larger value fails to work around the problem. While not perfect, it
is better than just failing the call. A similar workaround is already
implemented in the rtc-tps6586x driver.

Drop error messages in cros_ec_rtc_get() and cros_ec_rtc_set() since the
calling code also logs an error and to avoid spurious error messages if
setting the alarm ultimately succeeds.

Cc: Brian Norris <briannorris@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/rtc/rtc-cros-ec.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/drivers/rtc/rtc-cros-ec.c b/drivers/rtc/rtc-cros-ec.c
index 887f5193e253..a3ec066d8066 100644
--- a/drivers/rtc/rtc-cros-ec.c
+++ b/drivers/rtc/rtc-cros-ec.c
@@ -14,6 +14,8 @@
 
 #define DRV_NAME	"cros-ec-rtc"
 
+#define SECS_PER_DAY	(24 * 60 * 60)
+
 /**
  * struct cros_ec_rtc - Driver data for EC RTC
  *
@@ -43,13 +45,8 @@ static int cros_ec_rtc_get(struct cros_ec_device *cros_ec, u32 command,
 	msg.msg.insize = sizeof(msg.data);
 
 	ret = cros_ec_cmd_xfer_status(cros_ec, &msg.msg);
-	if (ret < 0) {
-		dev_err(cros_ec->dev,
-			"error getting %s from EC: %d\n",
-			command == EC_CMD_RTC_GET_VALUE ? "time" : "alarm",
-			ret);
+	if (ret < 0)
 		return ret;
-	}
 
 	*response = msg.data.time;
 
@@ -59,7 +56,7 @@ static int cros_ec_rtc_get(struct cros_ec_device *cros_ec, u32 command,
 static int cros_ec_rtc_set(struct cros_ec_device *cros_ec, u32 command,
 			   u32 param)
 {
-	int ret = 0;
+	int ret;
 	struct {
 		struct cros_ec_command msg;
 		struct ec_response_rtc data;
@@ -71,13 +68,8 @@ static int cros_ec_rtc_set(struct cros_ec_device *cros_ec, u32 command,
 	msg.data.time = param;
 
 	ret = cros_ec_cmd_xfer_status(cros_ec, &msg.msg);
-	if (ret < 0) {
-		dev_err(cros_ec->dev, "error setting %s on EC: %d\n",
-			command == EC_CMD_RTC_SET_VALUE ? "time" : "alarm",
-			ret);
+	if (ret < 0)
 		return ret;
-	}
-
 	return 0;
 }
 
@@ -190,8 +182,21 @@ static int cros_ec_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 
 	ret = cros_ec_rtc_set(cros_ec, EC_CMD_RTC_SET_ALARM, alarm_offset);
 	if (ret < 0) {
-		dev_err(dev, "error setting alarm: %d\n", ret);
-		return ret;
+		if (ret == -EINVAL && alarm_offset >= SECS_PER_DAY) {
+			/*
+			 * RTC chips on some older Chromebooks can only handle
+			 * alarms up to 24h in the future. Try to set an alarm
+			 * below that limit to avoid suspend failures.
+			 */
+			ret = cros_ec_rtc_set(cros_ec, EC_CMD_RTC_SET_ALARM,
+					      SECS_PER_DAY - 1);
+		}
+
+		if (ret < 0) {
+			dev_err(dev, "error setting alarm in %u seconds: %d\n",
+				alarm_offset, ret);
+			return ret;
+		}
 	}
 
 	return 0;
-- 
2.36.2