watchdog: cadence: Add expire_now method

It is working in a way that only minimal timeout is setup to reach
expiration just right after it is setup.
Please make sure that PMUFW is compiled with ENABLE_EM flag.

On U-Boot prompt you can test it like:
ZynqMP> wdt dev watchdog@fd4d0000
ZynqMP> wdt list
watchdog@fd4d0000 (cdns_wdt)
ZynqMP> wdt dev
dev: watchdog@fd4d0000
ZynqMP> wdt expire
(And reset should happen here)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --git a/drivers/watchdog/cdns_wdt.c b/drivers/watchdog/cdns_wdt.c
index 966d010..6dfdd31 100644 (file)
--- a/drivers/watchdog/cdns_wdt.c
+++ b/drivers/watchdog/cdns_wdt.c
@@ -215,6 +215,45 @@ static int cdns_wdt_stop(struct udevice *dev)
 }
 
 /**
+ * cdns_wdt_expire_now - Expire the watchdog.
+ *
+ * @dev: Watchdog device
+ * @flags: Driver flags
+ *
+ * Access WDT and configure with minimal counter value to expire ASAP.
+ * Expiration issues system reset. When DEBUG is enabled count should be
+ * bigger to at least see debug message.
+ *
+ * Return: Always 0
+ */
+static int cdns_wdt_expire_now(struct udevice *dev, ulong flags)
+{
+       struct cdns_wdt_priv *priv = dev_get_priv(dev);
+       u32 data, count = 0;
+
+#if defined(DEBUG)
+       count = 0x40; /* Increase the value if you need more time */
+       debug("%s: Expire wdt%u\n", __func__, dev_seq(dev));
+#endif
+
+       cdns_wdt_writereg(&priv->regs->zmr, CDNS_WDT_ZMR_ZKEY_VAL);
+
+       count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;
+
+       /* Write counter access key first to be able write to register */
+       data = count | CDNS_WDT_REGISTER_ACCESS_KEY;
+       cdns_wdt_writereg(&priv->regs->ccr, data);
+
+       data = CDNS_WDT_ZMR_WDEN_MASK |  CDNS_WDT_ZMR_RSTEN_MASK |
+               CDNS_WDT_ZMR_ZKEY_VAL;
+
+       cdns_wdt_writereg(&priv->regs->zmr, data);
+       cdns_wdt_writereg(&priv->regs->restart, CDNS_WDT_RESTART_KEY);
+
+       return 0;
+}
+
+/**
  * cdns_wdt_probe - Probe call for the device.
  *
  * @dev: Handle to the udevice structure.
@@ -247,7 +286,7 @@ static const struct wdt_ops cdns_wdt_ops = {
        .start = cdns_wdt_start,
        .reset = cdns_wdt_reset,
        .stop = cdns_wdt_stop,
-       /* There is no bit/reg/support in IP for expire_now functionality */
+       .expire_now = cdns_wdt_expire_now,
 };
 
 static const struct udevice_id cdns_wdt_ids[] = {