Subject: [PATCH v1 2/2] watchdog: imx2_wdt: add set_pretimeout interface

From: [email-masked] (Guenter Roeck)
Date: Mon, 2 Nov 2015 21:25:57 -0800

On 11/02/2015 08:55 PM, Robin Gong wrote:
> On Mon, Nov 02, 2015 at 08:19:12PM -0800, Guenter Roeck wrote:
>> On 11/02/2015 07:29 PM, Robin Gong wrote:
>>> Enable set_pretimeout interface and trigger the pretimeout interrupt before
>>> watchdog timeout event happen.
>>>
>>> Signed-off-by: Robin Gong <[email-masked]>
>>> ---
>>>   drivers/watchdog/imx2_wdt.c | 67 ++++++++++++++++++++++++++++++++++++++++++++-
>>>   1 file changed, 66 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
>>> index 0bb1a1d..d3c6b07 100644
>>> --- a/drivers/watchdog/imx2_wdt.c
>>> +++ b/drivers/watchdog/imx2_wdt.c
>>> @@ -24,7 +24,9 @@
>>>   #include <linux/clk.h>
>>>   #include <linux/delay.h>
>>>   #include <linux/init.h>
>>> +#include <linux/interrupt.h>
>>>   #include <linux/io.h>
>>> +#include <linux/irq.h>
>>
>> Are those two new includes both needed ?
>>
> Yes, irq.h is not needed.
>>>   #include <linux/jiffies.h>
>>>   #include <linux/kernel.h>
>>>   #include <linux/module.h>
>>> @@ -52,12 +54,18 @@
>>>   #define IMX2_WDT_WRSR		0x04		/* Reset Status Register */
>>>   #define IMX2_WDT_WRSR_TOUT	(1 << 1)	/* -> Reset due to Timeout */
>>>
>>> +#define IMX2_WDT_WICR		0x06		/*Interrupt Control Register*/
>>> +#define IMX2_WDT_WICR_WIE	(1 << 15)	/* -> Interrupt Enable */
>>> +#define IMX2_WDT_WICR_WTIS	(1 << 14)	/* -> Interrupt Status */
>>> +#define IMX2_WDT_WICR_WICT	(0xFF << 0)	/* Watchdog Interrupt Timeout */
>>> +
>>
>> "<< 0" doesn't really add any value here.
>>
> Accept.
>>>   #define IMX2_WDT_WMCR		0x08		/* Misc Register */
>>>
>>>   #define IMX2_WDT_MAX_TIME	128
>>>   #define IMX2_WDT_DEFAULT_TIME	60		/* in seconds */
>>>
>>>   #define WDOG_SEC_TO_COUNT(s)	((s * 2 - 1) << 8)
>>> +#define WDOG_SEC_TO_PRECOUNT(s)	(s * 2)		/* set WDOG pre timeout count*/
>>>
>> 					((s) * 2)
>>
>> Ah yes, WDOG_SEC_TO_COUNT should also use (s).
>>
>
>>>   struct imx2_wdt_device {
>>>   	struct clk *clk;
>>> @@ -80,7 +88,8 @@ MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
>>>
>>>   static const struct watchdog_info imx2_wdt_info = {
>>>   	.identity = "imx2+ watchdog",
>>> -	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
>>> +	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE
>>> +		   | WDIOF_PRETIMEOUT,
>>>   };
>>>
>>>   static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
>>> @@ -207,12 +216,59 @@ static inline void imx2_wdt_ping_if_active(struct watchdog_device *wdog)
>>>   	}
>>>   }
>>>
>>> +static int imx2_wdt_check_pretimeout_set(struct imx2_wdt_device *wdev)
>>> +{
>>> +	u32 val;
>>> +
>>> +	regmap_read(wdev->regmap, IMX2_WDT_WICR, &val);
>>> +	return (val & IMX2_WDT_WICR_WIE) ? 1 : 0;
>>
>> I don't understand the point of this function.
>> You check if IMX2_WDT_WICR_WIE is set,
>>
> Yes, looks no need check,just directly set this bit.
>>> +}
>>> +
>>> +static int imx2_wdt_set_pretimeout(struct watchdog_device *wdog,
>>> +				   unsigned int new_timeout)
>>> +{
>>> +	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
>>> +	u32 val;
>>> +
>>> +	regmap_read(wdev->regmap, IMX2_WDT_WICR, &val);
>>> +	/* set the new pre-timeout value in the WSR */
>>> +	val &= ~IMX2_WDT_WICR_WICT;
>>> +	val |= WDOG_SEC_TO_PRECOUNT(new_timeout);
>>> +
>>
>> What is the time here ? Is pretimeout the number of seconds
>> until the interrupt occurs, or the number of seconds before the actual
>> timeout (as per API) ?
>>
> The latter is.
>>> +	if (!imx2_wdt_check_pretimeout_set(wdev))
>>> +		val |= IMX2_WDT_WICR_WIE;	/*enable*/
>>
>> if IMX2_WDT_WICR_WIE is not set, you set it,
>>
>>> +
>>> +	regmap_write(wdev->regmap, IMX2_WDT_WICR, val);
>>> +
>>
>> and write the result unconditionally. Unless I am missing something,
>>
>> 	regmap_write, wdev->regmap, IMX2_WDT_WICR, val | IMX2_WDT_WICR_WIE);
>>
>> would accomplish exactly the same.
>>
>>> +	wdog->pretimeout = new_timeout;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static irqreturn_t imx2_wdt_isr(int irq, void *dev_id)
>>> +{
>>> +	struct platform_device *pdev = dev_id;
>>> +	struct watchdog_device *wdog = platform_get_drvdata(pdev);
>>> +	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
>>> +	u32 val;
>>> +
>>> +	regmap_read(wdev->regmap, IMX2_WDT_WICR, &val);
>>> +	if (val & IMX2_WDT_WICR_WTIS) {
>>> +		/*clear interrupt status bit*/
>>> +		regmap_write(wdev->regmap, IMX2_WDT_WICR, val);
>>> +		dev_warn(&pdev->dev, "pre-timeout:%d, %d Seconds remained\n",
>>> +			 wdog->pretimeout, wdog->timeout - wdog->pretimeout);
>>
>> The idea here is that this should trigger a panic.
>>
> Just add a print message, our customer will add what they want here.

We should follow kernel expectations and guidelines, and not expect customers
to make changes. After all, this is for the upstream kernel, not for a vendor
kernel. You can as well call panic here and let your customers change that
if they don't like it.

Guenter

>>> +	}
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>>   static const struct watchdog_ops imx2_wdt_ops = {
>>>   	.owner = THIS_MODULE,
>>>   	.start = imx2_wdt_start,
>>>   	.stop = imx2_wdt_stop,
>>>   	.ping = imx2_wdt_ping,
>>>   	.set_timeout = imx2_wdt_set_timeout,
>>> +	.set_pretimeout = imx2_wdt_set_pretimeout,
>>>   };
>>>
>>>   static const struct regmap_config imx2_wdt_regmap_config = {
>>> @@ -229,6 +285,7 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>>>   	struct resource *res;
>>>   	void __iomem *base;
>>>   	int ret;
>>> +	int irq;
>>>   	u32 val;
>>>
>>>   	wdev = devm_kzalloc(&pdev->dev, sizeof(*wdev), GFP_KERNEL);
>>> @@ -253,6 +310,14 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>>>   		return PTR_ERR(wdev->clk);
>>>   	}
>>>
>>> +	irq = platform_get_irq(pdev, 0);
>>
>> This makes the irq mandatory. What if a platform doesn't have one configured ?
>>
>>> +	ret = devm_request_irq(&pdev->dev, irq, imx2_wdt_isr, 0,
>>> +			       dev_name(&pdev->dev), pdev);
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "can't get irq %d\n", irq);
>>
>> You got it, but you could not request it.
>>
>> This is also a bit early, as the interrupt handler uses variables which are not yet
>> initialized.
>>
> Accept.
>>> +		return ret;
>>> +	}
>>> +
>>>   	wdog			= &wdev->wdog;
>>>   	wdog->info		= &imx2_wdt_info;
>>>   	wdog->ops		= &imx2_wdt_ops;
>>>
>>
>