On 02/05/2016 01:13 PM, Kyle Roeschley wrote:
On Fri, Feb 05, 2016 at 02:08:03PM -0600, Josh Cartwright wrote:
On Thu, Feb 04, 2016 at 07:28:02PM -0600, Kyle Roeschley wrote:
[..]
diff --git a/drivers/watchdog/ni9x3x_wdt.c b/drivers/watchdog/ni9x3x_wdt.c
index 13f5c10..1fce4d0 100644
--- a/drivers/watchdog/ni9x3x_wdt.c
+++ b/drivers/watchdog/ni9x3x_wdt.c
@@ -15,6 +15,7 @@
#include <linux/acpi.h>
#include <linux/interrupt.h>
#include <linux/module.h>
+#include <linux/sysfs.h>
#include <linux/watchdog.h>
#define NIWD_CONTROL 0x01
@@ -28,6 +29,7 @@
#define NIWD_IO_SIZE 0x08
#define NIWD_CONTROL_MODE 0x80
+#define NIWD_CONTROL_PROC_INTERRUPT 0x40
#define NIWD_CONTROL_PROC_RESET 0x20
#define NIWD_CONTROL_PET 0x10
#define NIWD_CONTROL_RUNNING 0x08
@@ -48,6 +50,7 @@ struct ni9x3x_wdt {
struct acpi_device *acpi_device;
u16 io_base;
u16 io_size;
+ u32 irq;
Interrupts have type 'int'.
spinlock_t lock;
struct watchdog_device wdog;
};
@@ -101,6 +104,34 @@ static unsigned int ni9x3x_wdt_wdd_get_timeleft(struct watchdog_device *wdd)
return (unsigned int)((counter * (u64)NIWD_PERIOD_NS) / 1000000000);
}
+static irqreturn_t ni9x3x_wdt_irq_handler(int irq, void *data)
+{
+ struct ni9x3x_wdt *wdt = data;
+ irqreturn_t ret = IRQ_NONE;
+ u8 control;
+ unsigned long flags;
+
+ spin_lock_irqsave(&wdt->lock, flags);
Interrupts are disabled already, so the _irqsave()/_irqrestore() is
unnecessary.
+
+ control = inb(wdt->io_base + NIWD_CONTROL);
+
+ if (!(NIWD_CONTROL_ALARM & control)) {
+ dev_err(&wdt->acpi_device->dev,
+ "Spurious watchdog interrupt, 0x%02X\n", control);
No need to print anything here, just return IRQ_NONE. The irq core will
print a much better (and rate-limited) error when/if this occurs.
+ goto out_unlock;
+ }
+
+ /* Acknowledge the interrupt. */
+ outb(control | NIWD_CONTROL_RESET, wdt->io_base + NIWD_CONTROL);
+
+ ret = IRQ_HANDLED;
+
+out_unlock:
+ spin_unlock_irqrestore(&wdt->lock, flags);
+
+ return ret;
+}
This is...strange. You're allowing a user to enable an interrupt reset
action, but...there is no way that a user can actually _do_ anything
when that action occurs.
I'm reminded of one of these:
https://www.youtube.com/watch?v=aqAUmgE3WyM
(The only reason I can think of where this would be a legitimate thing
to do was if we were relying on the watchdog interrupt to bring the CPU
out of a low power state...but AFAIK that's not something we do).
Josh
This is another reason (that I forgot to mention) for this being an RFC.
Ideally we'd poll or select the /dev/watchdogN file to wait on interrupt, but
this isn't supported by the watchdog core. My next instinct would be to have an
sysfs attribute named interrupt or event which a user could read/poll/select
to look for a 1 value indicating that an interrupt has occurred. Else, maybe
polling support could be added to the core, but I don't expect it would be very
useful.
I _really_ get the impression that you are trying to use the watchdog
subsystem for something it isn't supposed to support. poll/select on the
watchdog device is pretty much the opposite of what should happen.
the watchdog device node is intended to be written to to trigger a
heartbeat, not a device to use to wait for an interrupt. There is
no way we'll ever add support for this into the watchdog subsystem.
I'll really have to spend much more time on this, probably much more than
I have. I would suggest to either implement a traditional, standard,
watchdog driver, or consider implementing a non-watchdog driver if
your use case is that much different.
Thanks,
Guenter
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