On 2/18/25 19:41, Heyi Guo wrote:
Hi Guenter,
Thanks for your comments.
On 2025/2/18 13:33, Guenter Roeck wrote:
On 2/17/25 19:16, Heyi Guo wrote:
Aspeed watchdog uses counting down logic, so the value set to register
should be the value of subtracting pretimeout from total timeout.
Fixes: 9ec0b7e06835 ("watchdog: aspeed: Enable pre-timeout interrupt")
Signed-off-by: Heyi Guo <guoheyi@xxxxxxxxxxxxxxxxx>
Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Joel Stanley <joel@xxxxxxxxx>
Cc: Andrew Jeffery <andrew@xxxxxxxxxxxxxxxxxxxx>
Cc: Eddie James <eajames@xxxxxxxxxxxxx>
---
drivers/watchdog/aspeed_wdt.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
index b4773a6aaf8c..520d8aba12a5 100644
--- a/drivers/watchdog/aspeed_wdt.c
+++ b/drivers/watchdog/aspeed_wdt.c
@@ -187,6 +187,13 @@ static int aspeed_wdt_set_pretimeout(struct watchdog_device *wdd,
u32 actual = pretimeout * WDT_RATE_1MHZ;
u32 s = wdt->cfg->irq_shift;
u32 m = wdt->cfg->irq_mask;
+ u32 reload = readl(wdt->base + WDT_RELOAD_VALUE);
+
It is unusual to use a register value here and not the configured timeout
value. I would have assumed that pretimeout is compared against wdt->timout,
not against the register value, and that the multiplication with WDT_RATE_1MHZ
is done after validation. This needs an explanation.
It was supposed to be a straight-forward way to check if the pretimeout value is supported by the hardware. I can change to wdt->timeout if it is better.
Further, in the case of wdt->timeout > max_hw_heartbeat_ms, shall we restrict the pretimeout to be larger than wdt->timeout - max_hw_heartbeat_ms / 2? For the watchdog_kworker works in max_hw_heartbeat_ms / 2 interval, pretimeout event may be triggered unexpected when watchdog is not pinged in (max_hw_heartbeat_ms - (timeout - pretimeout)).
The kernel internal logic should handle that. If not, it needs to be modified/fixed.
+ if (actual >= reload)
+ return -EINVAL;
+
On top of that, you'll also need to explain why watchdog_pretimeout_invalid()
and with it the validation in watchdog_set_pretimeout() does not work for this
watchdog and why this extra validation is necessary.
watchdog_pretimeout_invalid() will return false if wdt->timeout == 0, but we can't determine the hardware pretimeout value if timeout == 0 here.
Sorry, I don't understand what you mean. If watchdog_pretimeout_invalid()
returns false if timeout == 0, aspeed_wdt_set_pretimeout() won't be called.
Why does that preclude depending on it ?
On a side note, I do wonder why the driver accepts a timeout value of 0 seconds.
Guenter
