On Tue, Jan 30, 2024 at 10:37:50PM -0800, Guenter Roeck wrote: > On 1/30/24 22:16, Pavan Kondeti wrote: > > On Tue, Jan 30, 2024 at 10:01:15PM -0800, Guenter Roeck wrote: > > > On 1/30/24 20:15, Pavankumar Kondeti wrote: > > > > When CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is enabled, kernel can pet the > > > > watchdog until user space takes over. Make use of this feature and > > > > start the watchdog in probe. > > > > > > > > Signed-off-by: Pavankumar Kondeti <quic_pkondeti@xxxxxxxxxxx> > > > > --- > > > > drivers/watchdog/qcom-wdt.c | 6 +++++- > > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c > > > > index 9e790f0c2096..4fb5dbf5faee 100644 > > > > --- a/drivers/watchdog/qcom-wdt.c > > > > +++ b/drivers/watchdog/qcom-wdt.c > > > > @@ -276,12 +276,16 @@ static int qcom_wdt_probe(struct platform_device *pdev) > > > > watchdog_init_timeout(&wdt->wdd, 0, dev); > > > > /* > > > > + * Kernel can pet the watchdog until user space takes over. > > > > + * Start the watchdog here to make use of this feature. > > > > + > > > > > > No, that is not what CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is about. > > > Please see its description. > > > > > > NACK. > > > > > Thanks for taking a look Guenter. I thought of using > > WATCHDOG_HANDLE_BOOT_ENABLED and infiniite open timeout as a hint to start > > the watchdog in probe. After seeing your NACK for this patch, I guess > > that would also would have been rejected. > > > WATCHDOG_HANDLE_BOOT_ENABLED is not supposed to be used in drivers. > It is a flag for the watchdog core. Before you bring it up, stm32_iwdg.c > is a corner case because (presumably) the driver can not determine > if the watchdog is running. > > > Do you think we can revive this [1] to add support for watchdog pet from > > the kernel? It would be helpful in cases where the user space has no > > support for watchdog pet (say minimal ramdisk). > > > > If done properly, sure. Looking at the exchange, the patch still had issues > which I don't think were ever resolved. Thanks. I will take a look at your review feedback on the series and address them before sending the next revision. > > Personally I would not want to rely on this, though. It won't address situations > where userspace hangs but low level kernel interrupts still work. I think > it is mostly useful to cover the time from loading the watchdog driver > to starting the watchdog daemon, but even that would better be solved by > starting the watchdog in the ROM monitor or BIOS. A minimal watchdog daemon > would not consume that much memory, so I don't think "user space has no > support for watchdog pet (say minimal ramdisk)" would ever be a real problem. > Such a minimal system would probably (hopefully) be based on busybox which > does support a watchdog. > Got it. I will find ways to start the watchdog in firmware so that we don't need anything special handling. Thanks, Pavan
