watchdog: rti: support SPL (or re-start)

If the RTI watchdog has been enabled in SPL, enabling it in U-Boot proper
fails because it can only be enabled once in HW and never stopped. This
however leads to a situation that wdt_cyclic() watchdog trigger is not
being started any longer and the WDT fires at some point.

Allow for WDT re-start by not bailing out if the [previously] configured
period matches the one to be configured.

Enabling in [A53] SPL has been tested on AM62x-based HW (where [A53] SPL is
responsible for loading R5 DM firmware and not this driver).

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 99168d0..320c5ca 100644 (file)
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -131,18 +131,19 @@ static int rti_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
        u32 timer_margin;
        int ret;
 
-       if (readl(priv->regs + RTIDWDCTRL) == WDENABLE_KEY)
+       timer_margin = timeout_ms * priv->clk_hz / 1000;
+       timer_margin >>= WDT_PRELOAD_SHIFT;
+       if (timer_margin > WDT_PRELOAD_MAX)
+               timer_margin = WDT_PRELOAD_MAX;
+
+       if (readl(priv->regs + RTIDWDCTRL) == WDENABLE_KEY &&
+           readl(priv->regs + RTIDWDPRLD) != timer_margin)
                return -EBUSY;
 
        ret = rti_wdt_load_fw(dev);
        if (ret < 0)
                return ret;
 
-       timer_margin = timeout_ms * priv->clk_hz / 1000;
-       timer_margin >>= WDT_PRELOAD_SHIFT;
-       if (timer_margin > WDT_PRELOAD_MAX)
-               timer_margin = WDT_PRELOAD_MAX;
-
        writel(timer_margin, priv->regs + RTIDWDPRLD);
        writel(RTIWWDRX_NMI, priv->regs + RTIWWDRXCTRL);
        writel(RTIWWDSIZE_50P, priv->regs + RTIWWDSIZECTRL);