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Subject: Re: [PATCH v4] watchdog: qcom: support pre-timeout when the bark irq
 is available
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     agross@kernel.org, wim@linux-watchdog.org,
        bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
        linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190905210035.9985-1-jorge.ramirez-ortiz@linaro.org>
 <20190905211913.GA31094@roeck-us.net>
From:   Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
Message-ID: <68ca07e6-efa2-d5bd-111b-faaa86808192@linaro.org>
Date:   Thu, 5 Sep 2019 23:34:03 +0200
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On 9/5/19 23:19, Guenter Roeck wrote:
> On Thu, Sep 05, 2019 at 11:00:35PM +0200, Jorge Ramirez-Ortiz wrote:
>> Use the bark interrupt as the pre-timeout notifier whenever this
>> interrupt is available.
>>
>> By default, the pretimeout notification shall occur one second earlier
>> than the timeout.
>>
>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
>> ---
>>  v4:
>>      address Guenter Roeck comments as follows:
>>        remove unnecessary include and private variable
>>        provide macro for WDT EN register values
>>        use pretimeout as per its API intent
>>        handle EPROBE_DEFER on get_irq
>>      also:
>>        handle the irq registration as done in pm8916_wdt.c
>>  v3:
>>     remove unnecesary variable added to private.
>>
>>  v2:
>>     register the pre-timeout notifier instead.
>>
>>  v1:
>>  drivers/watchdog/qcom-wdt.c | 64 ++++++++++++++++++++++++++++++++++---
>>  1 file changed, 59 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
>> index 7be7f87be28f..0f1d29eeb81d 100644
>> --- a/drivers/watchdog/qcom-wdt.c
>> +++ b/drivers/watchdog/qcom-wdt.c
>> @@ -10,6 +10,7 @@
>>  #include <linux/platform_device.h>
>>  #include <linux/watchdog.h>
>>  #include <linux/of_device.h>
>> +#include <linux/interrupt.h>
>>  
>>  enum wdt_reg {
>>  	WDT_RST,
>> @@ -19,6 +20,9 @@ enum wdt_reg {
>>  	WDT_BITE_TIME,
>>  };
>>  
>> +#define QCOM_WDT_ENABLE		BIT(0)
>> +#define QCOM_WDT_ENABLE_IRQ	BIT(1)
>> +
> 
> Using BIT() requires "#include <linux/bits.h>".

do you want it explicitly in the file even if it builds?

> 
>>  static const u32 reg_offset_data_apcs_tmr[] = {
>>  	[WDT_RST] = 0x38,
>>  	[WDT_EN] = 0x40,
>> @@ -54,15 +58,38 @@ struct qcom_wdt *to_qcom_wdt(struct watchdog_device *wdd)
>>  	return container_of(wdd, struct qcom_wdt, wdd);
>>  }
>>  
>> +static inline int qcom_get_enable(struct watchdog_device *wdd)
>> +{
>> +	int enable = QCOM_WDT_ENABLE;
>> +
>> +	if (wdd->info->options & WDIOF_PRETIMEOUT)
>> +		enable |= QCOM_WDT_ENABLE_IRQ;
>> +
> 
> Again, the condition needs to be that pretimeout != 0,
> not that it is supported.

no I dont think so. doing that would propagate a possible error in some
pretimeout setup code which would end up enabling an interrupt when it
shouldnt. so I dont think that doing that would be correct.

The interrupt should only be enabled if WDIOF_PRETIMEOUT is configured
(independently of the pretimeout value); as a matter of fact, if
pretimeout is 0, the interrupt will trigger at the same time than bark
(which is what the original code used to do).

so I'd rather keep this condition unless you strongly oppose to it.

> 
>> +	return enable;
>> +}
>> +
>> +static irqreturn_t qcom_wdt_isr(int irq, void *arg)
>> +{
>> +	struct watchdog_device *wdd = arg;
>> +
>> +	watchdog_notify_pretimeout(wdd);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>>  static int qcom_wdt_start(struct watchdog_device *wdd)
>>  {
>>  	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
>> +	unsigned int bark = wdd->timeout;
>> +
>> +	if (wdd->pretimeout)
>> +		bark = bark - wdd->pretimeout;
> 
> The if() just adds code and doesn't otherwise do any good.

yeah, was just for clarity and it is surely removed by the compiler. but
sure will remove

> 
>>  
>>  	writel(0, wdt_addr(wdt, WDT_EN));
>>  	writel(1, wdt_addr(wdt, WDT_RST));
>> -	writel(wdd->timeout * wdt->rate, wdt_addr(wdt, WDT_BARK_TIME));
>> +	writel(bark * wdt->rate, wdt_addr(wdt, WDT_BARK_TIME));
>>  	writel(wdd->timeout * wdt->rate, wdt_addr(wdt, WDT_BITE_TIME));
>> -	writel(1, wdt_addr(wdt, WDT_EN));
>> +	writel(qcom_get_enable(wdd), wdt_addr(wdt, WDT_EN));
>>  	return 0;
>>  }
>>  
>> @@ -89,6 +116,13 @@ static int qcom_wdt_set_timeout(struct watchdog_device *wdd,
>>  	return qcom_wdt_start(wdd);
>>  }
>>  
>> +static int qcom_wdt_set_pretimeout(struct watchdog_device *wdd,
>> +				   unsigned int timeout)
>> +{
>> +	wdd->pretimeout = timeout;
>> +	return qcom_wdt_start(wdd);
>> +}
>> +
>>  static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
>>  			    void *data)
>>  {
>> @@ -105,7 +139,7 @@ static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
>>  	writel(1, wdt_addr(wdt, WDT_RST));
>>  	writel(timeout, wdt_addr(wdt, WDT_BARK_TIME));
>>  	writel(timeout, wdt_addr(wdt, WDT_BITE_TIME));
>> -	writel(1, wdt_addr(wdt, WDT_EN));
>> +	writel(qcom_get_enable(wdd), wdt_addr(wdt, WDT_EN));
>>  
>>  	/*
>>  	 * Actually make sure the above sequence hits hardware before sleeping.
>> @@ -121,6 +155,7 @@ static const struct watchdog_ops qcom_wdt_ops = {
>>  	.stop		= qcom_wdt_stop,
>>  	.ping		= qcom_wdt_ping,
>>  	.set_timeout	= qcom_wdt_set_timeout,
>> +	.set_pretimeout	= qcom_wdt_set_pretimeout,
>>  	.restart        = qcom_wdt_restart,
>>  	.owner		= THIS_MODULE,
>>  };
>> @@ -133,6 +168,15 @@ static const struct watchdog_info qcom_wdt_info = {
>>  	.identity	= KBUILD_MODNAME,
>>  };
>>  
>> +static const struct watchdog_info qcom_wdt_pt_info = {
>> +	.options	= WDIOF_KEEPALIVEPING
>> +			| WDIOF_MAGICCLOSE
>> +			| WDIOF_SETTIMEOUT
>> +			| WDIOF_PRETIMEOUT
>> +			| WDIOF_CARDRESET,
>> +	.identity	= KBUILD_MODNAME,
>> +};
>> +
>>  static void qcom_clk_disable_unprepare(void *data)
>>  {
>>  	clk_disable_unprepare(data);
>> @@ -146,7 +190,7 @@ static int qcom_wdt_probe(struct platform_device *pdev)
>>  	struct device_node *np = dev->of_node;
>>  	const u32 *regs;
>>  	u32 percpu_offset;
>> -	int ret;
>> +	int irq, ret;
>>  
>>  	regs = of_device_get_match_data(dev);
>>  	if (!regs) {
>> @@ -204,7 +248,17 @@ static int qcom_wdt_probe(struct platform_device *pdev)
>>  		return -EINVAL;
>>  	}
>>  
>> -	wdt->wdd.info = &qcom_wdt_info;
>> +	irq = platform_get_irq(pdev, 0);
>> +	if (irq > 0) {
>> +		if (devm_request_irq(dev, irq, qcom_wdt_isr,
>> +				     IRQF_TRIGGER_RISING, "wdt_bark",
>> +				     &wdt->wdd))
>> +			irq = 0;
>> +	} else if (irq == -EPROBE_DEFER)
>> +		return -EPROBE_DEFER;
>> +
>> +	wdt->wdd.info = irq > 0 ? &qcom_wdt_pt_info : &qcom_wdt_info;
>> +	wdt->wdd.pretimeout = irq > 0 ? 1 : 0;
> 
> Why repeat the conditional ? It seems to me that something like
> 
> 	wdt->wdd.info = &qcom_wdt_info;
> 	...
> 	if (irq > 0) {
> 		wdt->wdd.info = &qcom_wdt_pt_info;
> 		wdt->wdd.pretimeout = 1;
> 		...
> 	}
> 
> would be much easier and avoid the repeated conditionals.

I agree. will change.

> 
>>  	wdt->wdd.ops = &qcom_wdt_ops;
>>  	wdt->wdd.min_timeout = 1;
>>  	wdt->wdd.max_timeout = 0x10000000U / wdt->rate;
>> -- 
>> 2.23.0
>>
>