On 11/12/2015 06:06 PM, Al Stone wrote:
If it is a NAK, that's fine, but I also want to be sure I understand what the
objections are. Based on my understanding of the discussion so far over the
multiple versions, I think the primary objection is that the use of pretimeout
makes this driver too complex, and indeed complex enough that there is some
concern that it could destabilize a running system. Do I have that right?
I don't have a problem with the concept of pre-timeout per se. My
primary objection is this code:
> +static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id)
> +{
> + struct sbsa_gwdt *gwdt = (struct sbsa_gwdt *)dev_id;
> + struct watchdog_device *wdd = &gwdt->wdd;
> +
> + /* We don't use pretimeout, trigger WS1 now */
> + if (!wdd->pretimeout)
> + sbsa_gwdt_set_wcv(wdd, 0);
This driver depends on an interrupt handler in order to properly program
the hardware. Unlike some other devices, the SBSA watchdog does not
need assistance to reset on a timeout -- it is a "fire and forget"
device. What happens if there is a hard lockup, and interrupts no
longer work?
The reason why Fu does this is because he wants to support a pre-timeout
value that's independent of the timeout value. The SBSA watchdog is
normally programmed where real timeout equals twice the pre-timeout. I
would prefer that the driver adhere to this limitation. That would
eliminate the need to pre-program the hardware in the interrupt handler.
And finally, a simpler, single stage timeout watchdog driver would be a
reasonable thing to accept, yes? I can see where that would make sense.
I would be okay with merging such a driver, and then enhancing it later
to add pre-timeout support.
The issue for me in that case is that the SBSA requires a two stage timeout,
so a single stage driver has no real value for me.
There are plenty of existing watchdog devices that have a two-stage
timeout but the driver treats it as a single stage. The PowerPC
watchdog driver is like that. The hardware is programmed for the second
stage to cause a hardware reset, and the interrupt handler is typically
a no-op or just a printk().
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