[bug] can't start watchdog on RK3288

[Marius Dinu]

On Tue, 2025-10-14 19.12.23 ++0100, Peter Robinson wrote:
> Hi,
> 
> > I have a bug to report. I tried starting the watchdog on Asus TinkerBoard S
> > (Rockchip RK3288), but it's not working. I investigated a little bit. Here's
> > what I found so far:
> 
> What version of U-Boot is this? Does the watchdog work in Linux?
> 
> > => wdt dev watchdog at ff800000
> > drivers/core/ofnode.c:417-ofnode_read_u32_index() ofnode_read_u32_index: timeout-sec: (not found)
> > drivers/core/ofnode.c:417-ofnode_read_u32_index() ofnode_read_u32_index: hw_margin_ms: (not found)
> > drivers/core/ofnode.c:525-    ofnode_read_bool() ofnode_read_bool: u-boot,noautostart: false
> > drivers/core/ofnode.c:525-    ofnode_read_bool() ofnode_read_bool: u-boot,autostart: false
> > drivers/core/ofnode.c:540-    ofnode_read_prop() ofnode_read_prop: assigned-clock-rates: <not found>
> > drivers/core/uclass.c:546-uclass_get_device_by_ofnode() Looking for clock-controller at ff760000
> > drivers/core/uclass.c:397-uclass_find_device_by_ofnode() Looking for clock-controller at ff760000
> > drivers/core/uclass.c:406-uclass_find_device_by_ofnode()       - checking oscillator
> > drivers/core/uclass.c:406-uclass_find_device_by_ofnode()       - checking clock-controller at ff760000
> > drivers/core/uclass.c:416-uclass_find_device_by_ofnode()    - result for clock-controller at ff760000: clock-controller at ff760000 (ret=0)
> > drivers/core/uclass.c:549-uclass_get_device_by_ofnode()    - result for clock-controller at ff760000: clock-controller at ff760000 (ret=0)
> > Can't get the watchdog timer: watchdog at ff800000
> >
> > It seems that the error is generated in designware_wdt_probe(), after
> > clk_enable(). Function clk_enable() runs on branch CLK_CCF=false. It returns
> > error from ops->enable. Struct ops is defined by driver: rockchip_rk3288_cru,
> > in drivers/clk/rockchip/clk_rk3288.c, but it doesn't have a .enable or
> > .disable component, so there is no ops->enable.
> >
> > The solution to this one would probably be a stub for .enable. AFAIK, it's
> > always enabled.
> >
> > I also tried to enable CLK_CCF (drivers from Linux tree), selecting the
> > watchdog works, but if I try to start it, the board immediately resets.
> > I have no ideea how to troubleshoot this one.
> >
> > Thanks.
> > Marius
> >

I updated to latest u-boot (yesterday's github) and I patched clk_rk3288.c:

diff --git a/drivers/clk/rockchip/clk_rk3288.c b/drivers/clk/rockchip/clk_rk3288.c
index a4ff1c41abb..9cc883662ff 100644
--- a/drivers/clk/rockchip/clk_rk3288.c
+++ b/drivers/clk/rockchip/clk_rk3288.c
@@ -745,6 +745,10 @@ static ulong rockchip_saradc_set_clk(struct rockchip_cru *cru, uint hz)
 	return rockchip_saradc_get_clk(cru);
 }

+static int rk3288_clk_enable(struct clk *clk){
+	return 0;
+}
+
 static ulong rk3288_clk_get_rate(struct clk *clk)
 {
 	struct rk3288_clk_priv *priv = dev_get_priv(clk->dev);
@@ -947,6 +951,7 @@ static int __maybe_unused rk3288_clk_set_parent(struct clk *clk, struct clk *par
 }

 static struct clk_ops rk3288_clk_ops = {
+	.enable		= rk3288_clk_enable,
 	.get_rate	= rk3288_clk_get_rate,
 	.set_rate	= rk3288_clk_set_rate,
 #if CONFIG_IS_ENABLED(OF_REAL)

...and it works, but not exactly as it should.

wdt dev works
wdt start works, but the timeouts are all wrong
wdt reset works
wdt stop doesn't work

Timeouts:
wdt start 10000 => 1m27s until reset
wdt start 1000  => 1m27s
wdt start 200   => ~40s
wdt start 100   => ~10s
I measured timeouts while watching output via serial->microcom->ssh,
so they're not really precise.

Marius