linux-kernel - Re: [PATCH v4] watchdog: qcom: support pre-timeout when the bark irq is available

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Message-ID: <f06d0e52-11f4-c1e9-6e3b-30790dfec534@linaro.org>
Date:   Fri, 6 Sep 2019 21:15:24 +0200
From:   Jorge Ramirez <jorge.ramirez-ortiz@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     agross@...nel.org, linux@...ck-us.net, wim@...ux-watchdog.org,
        linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] watchdog: qcom: support pre-timeout when the bark irq
 is available

On 9/6/19 19:40, Bjorn Andersson wrote:
> On Thu 05 Sep 14:00 PDT 2019, Jorge Ramirez-Ortiz wrote:
>> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> [..]
>> +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;
> 
> Looking at downstream they conditionally write 3 to WDT_EN during
> initialization, but during suspend/resume they just set it to back to 1.
> 
> So I don't think you should touch BIT(1) (which name doesn't match
> downstream or the register documentation)

writing BIT(1) on the enable register is necessary to get the interrupt
and therefore to be notified of the bark event. this can not be avoided.

> 
>> +
>> +	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;
> 
> As Guenter points out, writing wdd->timeout - wdt->pretimeout to
> WDT_BARK_TIME unconditionally should do the trick.

yes

> 
>>  
>>  	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;
>>  }
> [..]
>> @@ -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))
> 
> A failure here means that a irq was specified in DT (platform_get_irq()
> returned > 0) but you failed to acquire request it, you should fail your
> probe() when this happens.

yeah that is what I thought but since pm8916-wdt.c has recently been
merged exactly like I copied above I chose to follow to avoid arguing
about this.

anyway I'll send a patch to fix pm8916-wdt.c and then will do it that
same way on this driver.

> 
>> +			irq = 0;
>> +	} else if (irq == -EPROBE_DEFER)
>> +		return -EPROBE_DEFER;
> 
> Some {} around this block please.

um, checkpatch didnt complain. anyway sure, will do

> 
> Regards,
> Bjorn
> 
>> +
>> +	wdt->wdd.info = irq > 0 ? &qcom_wdt_pt_info : &qcom_wdt_info;
>> +	wdt->wdd.pretimeout = irq > 0 ? 1 : 0;
>>  	wdt->wdd.ops = &qcom_wdt_ops;
>>  	wdt->wdd.min_timeout = 1;
>>  	wdt->wdd.max_timeout = 0x10000000U / wdt->rate;
>> -- 
>> 2.23.0
>>
>