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Date: Fri, 15 May 2015 06:33:57 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: fu.wei@...aro.org, Suravee.Suthikulpanit@....com,
linaro-acpi@...ts.linaro.org, linux-watchdog@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org
CC: tekkamanninja@...il.com, graeme.gregory@...aro.org,
al.stone@...aro.org, hanjun.guo@...aro.org, timur@...eaurora.org,
ashwin.chaugule@...aro.org, arnd@...db.de, vgandhi@...eaurora.org,
wim@...ana.be, jcm@...hat.com, leo.duran@....com, corbet@....net
Subject: Re: [PATCH 4/6] Watchdog: introdouce "pretimeout" into framework
On 05/15/2015 04:24 AM, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
>
> Reasons:
> (1)kernel already has two watchdog drivers are using "pretimeout":
> drivers/char/ipmi/ipmi_watchdog.c
> drivers/watchdog/kempld_wdt.c(but the definition is different)
> (2)some other dirvers are going to use this: ARM SBSA Generic Watchdog
>
> Signed-off-by: Fu Wei <fu.wei@...aro.org>
> ---
> drivers/watchdog/watchdog_core.c | 66 ++++++++++++++++++++++++++++++++++++++++
> drivers/watchdog/watchdog_dev.c | 48 +++++++++++++++++++++++++++++
> include/linux/watchdog.h | 19 ++++++++++++
> 3 files changed, 133 insertions(+)
>
> diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
> index cec9b55..6ca9578 100644
> --- a/drivers/watchdog/watchdog_core.c
> +++ b/drivers/watchdog/watchdog_core.c
> @@ -54,6 +54,14 @@ static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
> wdd->min_timeout = 0;
> wdd->max_timeout = 0;
> }
> + if (wdd->min_pretimeout && wdd->min_timeout < wdd->min_pretimeout) {
> + pr_info("Invalid min timeout, resetting to min pretimeout!\n");
> + wdd->min_timeout = wdd->min_pretimeout;
> + }
> + if (wdd->max_pretimeout && wdd->max_timeout < wdd->max_pretimeout) {
> + pr_info("Invalid max timeout, resetting to max pretimeout!\n");
> + wdd->max_timeout = wdd->max_pretimeout;
> + }
I am a bit concerned about the context dependency introduced here. If someone calls
_init_pretimeout after calling init_timeout, this may result in still invalid timeout
values.
> }
>
> /**
> @@ -98,6 +106,63 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
> }
> EXPORT_SYMBOL_GPL(watchdog_init_timeout);
>
> +static void watchdog_check_min_max_pretimeout(struct watchdog_device *wdd)
> +{
> + /*
> + * Check that we have valid min and max pretimeout values, if
> + * not reset them both to 0 (=not used or unknown)
> + */
> + if (wdd->min_pretimeout > wdd->max_pretimeout) {
> + pr_info("Invalid min and max pretimeout, resetting to 0!\n");
> + wdd->min_pretimeout = 0;
> + wdd->max_pretimeout = 0;
> + }
> +}
> +
> +/**
> + * watchdog_init_pretimeout() - initialize the pretimeout field
> + * @pretimeout_parm: pretimeout module parameter
> + * @dev: Device that stores the timeout-sec property
> + *
> + * Initialize the pretimeout field of the watchdog_device struct with either
> + * the pretimeout module parameter (if it is valid value) or the timeout-sec
> + * property (only if it is a valid value and the timeout_parm is out of bounds).
> + * If none of them are valid then we keep the old value (which should normally
> + * be the default pretimeout value.
> + *
> + * A zero is returned on success and -EINVAL for failure.
> + */
The new API function also needs to be documented in
Documentation/watchdog/watchdog-kernel-api.txt.
> +int watchdog_init_pretimeout(struct watchdog_device *wdd,
> + unsigned int pretimeout_parm, struct device *dev)
> +{
> + int ret = 0;
> + u32 timeouts[2];
> +
> + watchdog_check_min_max_pretimeout(wdd);
> +
> + /* try to get the timeout module parameter first */
> + if (!watchdog_pretimeout_invalid(wdd, pretimeout_parm) &&
> + pretimeout_parm) {
> + wdd->pretimeout = pretimeout_parm;
> + return ret;
> + }
> + if (pretimeout_parm)
> + ret = -EINVAL;
> +
> + /* try to get the timeout_sec property */
> + if (!dev || !dev->of_node)
> + return ret;
> + ret = of_property_read_u32_array(dev->of_node,
> + "timeout-sec", timeouts, 2);
> + if (!watchdog_pretimeout_invalid(wdd, timeouts[1]) && timeouts[1])
Guess we are still waiting for feedback from the devicetree maintainers on this.
Both the above synchronization concern and this makes me wonder if we should introduce
watchdog_init_timeouts() instead, which would take pretimeout as additional parameter.
What do you think about that ?
> + wdd->pretimeout = timeouts[1];
> + else
> + ret = -EINVAL;
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(watchdog_init_pretimeout);
> +
> /**
> * watchdog_register_device() - register a watchdog device
> * @wdd: watchdog device
> @@ -119,6 +184,7 @@ int watchdog_register_device(struct watchdog_device *wdd)
> if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
> return -EINVAL;
>
> + watchdog_check_min_max_pretimeout(wdd);
> watchdog_check_min_max_timeout(wdd);
>
> /*
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index 6aaefba..b519257 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -218,6 +218,38 @@ out_timeout:
> }
>
> /*
> + * watchdog_set_pretimeout: set the watchdog timer pretimeout
> + * @wddev: the watchdog device to set the timeout for
> + * @pretimeout: pretimeout to set in seconds
> + */
> +
> +static int watchdog_set_pretimeout(struct watchdog_device *wddev,
> + unsigned int pretimeout)
> +{
> + int err;
> +
> + if (!wddev->ops->set_pretimeout ||
> + !(wddev->info->options & WDIOF_PRETIMEOUT))
> + return -EOPNOTSUPP;
> +
> + if (watchdog_pretimeout_invalid(wddev, pretimeout))
> + return -EINVAL;
> +
> + mutex_lock(&wddev->lock);
> +
> + if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
> + err = -ENODEV;
> + goto out_pretimeout;
> + }
> +
> + err = wddev->ops->set_pretimeout(wddev, pretimeout);
> +
> +out_pretimeout:
> + mutex_unlock(&wddev->lock);
> + return err;
> +}
> +
> +/*
> * watchdog_get_timeleft: wrapper to get the time left before a reboot
> * @wddev: the watchdog device to get the remaining time from
> * @timeleft: the time that's left
> @@ -388,6 +420,22 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
> if (wdd->timeout == 0)
> return -EOPNOTSUPP;
> return put_user(wdd->timeout, p);
> + case WDIOC_SETPRETIMEOUT:
> + if (get_user(val, p))
> + return -EFAULT;
> + err = watchdog_set_pretimeout(wdd, val);
> + if (err < 0)
> + return err;
> + /* If the watchdog is active then we send a keepalive ping
> + * to make sure that the watchdog keep's running (and if
s/keep's/keeps/
> + * possible that it takes the new timeout) */
Please use the common multi-line comment style (that it isn't used above is not
an argument).
> + watchdog_ping(wdd);
> + /* Fall */
> + case WDIOC_GETPRETIMEOUT:
> + /* timeout == 0 means that we don't use the pretimeout */
> + if (wdd->pretimeout == 0)
> + return -EOPNOTSUPP;
> + return put_user(wdd->pretimeout, p);
> case WDIOC_GETTIMELEFT:
> err = watchdog_get_timeleft(wdd, &val);
> if (err)
> diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
> index a746bf5..f0a3c5b 100644
> --- a/include/linux/watchdog.h
> +++ b/include/linux/watchdog.h
> @@ -25,6 +25,7 @@ struct watchdog_device;
> * @ping: The routine that sends a keepalive ping to the watchdog device.
> * @status: The routine that shows the status of the watchdog device.
> * @set_timeout:The routine for setting the watchdog devices timeout value.
> + * @set_pretimeout:The routine for setting the watchdog devices pretimeout value
> * @get_timeleft:The routine that get's the time that's left before a reset.
> * @ref: The ref operation for dyn. allocated watchdog_device structs
> * @unref: The unref operation for dyn. allocated watchdog_device structs
> @@ -44,6 +45,7 @@ struct watchdog_ops {
> int (*ping)(struct watchdog_device *);
> unsigned int (*status)(struct watchdog_device *);
> int (*set_timeout)(struct watchdog_device *, unsigned int);
> + int (*set_pretimeout)(struct watchdog_device *, unsigned int);
> unsigned int (*get_timeleft)(struct watchdog_device *);
> void (*ref)(struct watchdog_device *);
> void (*unref)(struct watchdog_device *);
> @@ -62,6 +64,9 @@ struct watchdog_ops {
> * @timeout: The watchdog devices timeout value.
> * @min_timeout:The watchdog devices minimum timeout value.
> * @max_timeout:The watchdog devices maximum timeout value.
> + * @pretimeout: The watchdog devices pretimeout value.
> + * @min_pretimeout:The watchdog devices minimum pretimeout value.
> + * @max_pretimeout:The watchdog devices maximum pretimeout value.
> * @driver-data:Pointer to the drivers private data.
> * @lock: Lock for watchdog core internal use only.
> * @status: Field that contains the devices internal status bits.
> @@ -86,6 +91,9 @@ struct watchdog_device {
> unsigned int timeout;
> unsigned int min_timeout;
> unsigned int max_timeout;
> + unsigned int pretimeout;
> + unsigned int min_pretimeout;
> + unsigned int max_pretimeout;
> void *driver_data;
> struct mutex lock;
> unsigned long status;
> @@ -120,6 +128,14 @@ static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigne
> (t < wdd->min_timeout || t > wdd->max_timeout));
> }
>
> +/* Use the following function to check if a pretimeout value is invalid */
> +static inline bool watchdog_pretimeout_invalid(struct watchdog_device *wdd,
> + unsigned int t)
> +{
> + return ((wdd->max_pretimeout != 0) &&
> + (t < wdd->min_pretimeout || t > wdd->max_pretimeout));
> +}
> +
> /* Use the following functions to manipulate watchdog driver specific data */
> static inline void watchdog_set_drvdata(struct watchdog_device *wdd, void *data)
> {
> @@ -134,6 +150,9 @@ static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
> /* drivers/watchdog/watchdog_core.c */
> extern int watchdog_init_timeout(struct watchdog_device *wdd,
> unsigned int timeout_parm, struct device *dev);
> +extern int watchdog_init_pretimeout(struct watchdog_device *wdd,
> + unsigned int pretimeout_parm,
> + struct device *dev);
Please drop the 'extern'. Guess it may be time to clean up the watchdog core code ;-).
Thanks,
Guenter
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