[PATCH 2/4] watchdog: arm_smc_wdt: get wdt status through SMCWD_GET_TIMELEFT

[Antonio Borneo]

The optional SMCWD_GET_TIMELEFT command can be used to detect if
the watchdog has already been started.
See the implementation in OP-TEE secure OS [1].

At probe time, check if the watchdog is already started and then
call wdt_set_force_autostart(). This will keep U-Boot pinging the
watchdog even when the property 'u-boot,noautostart' is present.

Link: https://github.com/OP-TEE/optee_os/commit/a7f2d4bd8632 [1]

Signed-off-by: Antonio Borneo <antonio.borneo at foss.st.com>
---
 drivers/watchdog/arm_smc_wdt.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
index 0ea44445700..f6854aa9ac9 100644
--- a/drivers/watchdog/arm_smc_wdt.c
+++ b/drivers/watchdog/arm_smc_wdt.c
@@ -46,6 +46,8 @@ static int smcwd_call(struct udevice *dev, enum smcwd_call call,
 		return -ENODEV;
 	if (res->a0 == PSCI_RET_INVALID_PARAMS)
 		return -EINVAL;
+	if (res->a0 == PSCI_RET_DISABLED)
+		return -ENODATA;
 	if (res->a0 != PSCI_RET_SUCCESS)
 		return -EIO;
 
@@ -99,6 +101,21 @@ static int smcwd_probe(struct udevice *dev)
 	priv->min_timeout = res.a1;
 	priv->max_timeout = res.a2;
 
+	/* If already started, then force u-boot to use it */
+	err = smcwd_call(dev, SMCWD_GET_TIMELEFT, 0, NULL);
+	switch (err) {
+	case 0:
+		dev_dbg(dev, "Already started\n");
+		wdt_set_force_autostart(dev);
+		break;
+	case -ENODATA:
+		dev_dbg(dev, "Not already started\n");
+		break;
+	default:
+		/* Optional SMCWD_GET_TIMELEFT not implemented */
+		break;
+	}
+
 	return 0;
 }
 
-- 
2.34.1