linux-kernel - Re: [PATCH v12 4/4] Watchdog: introduce ARM SBSA watchdog driver

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Date:	Fri, 26 Feb 2016 13:27:39 -0600
From:	Timur Tabi <timur@...eaurora.org>
To:	fu.wei@...aro.org, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, wim@...ana.be, linux@...ck-us.net,
	corbet@....net, catalin.marinas@....com, will.deacon@....com,
	Suravee.Suthikulpanit@....com
Cc:	linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
	linux-doc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org,
	rruigrok@...eaurora.org, harba@...eaurora.org, cov@...eaurora.org,
	dyoung@...hat.com, panand@...hat.com, graeme.gregory@...aro.org,
	al.stone@...aro.org, hanjun.guo@...aro.org, jcm@...hat.com,
	arnd@...db.de, leo.duran@....com, sudeep.holla@....com
Subject: Re: [PATCH v12 4/4] Watchdog: introduce ARM SBSA watchdog driver

fu.wei@...aro.org wrote:
> +	if (action) {
> +		irq = platform_get_irq(pdev, 0);
> +		if (irq < 0) {
> +			action = 0;
> +			dev_warn(dev, "unable to get ws0 interrupt.\n");
> +		} else {
> +			if (devm_request_irq(dev, irq, sbsa_gwdt_interrupt, 0,
> +					     pdev->name, gwdt)) {
> +				action = 0;
> +				dev_warn(dev, "unable to request IRQ %d.\n",
> +					 irq);
> +			}
> +		}
> +		if (!action)
> +			dev_warn(dev, "falling back to signle stage mode.\n");
> +	}
> +
> +	/*
> +	 * Get the frequency of system counter from the cp15 interface of ARM
> +	 * Generic timer. We don't need to check it, because if it returns "0",
> +	 * system would panic in very early stage.
> +	 */
> +	gwdt->clk = arch_timer_get_cntfrq();
> +	gwdt->refresh_base = rf_base;
> +	gwdt->control_base = cf_base;

I think you need to ping the watchdog before enabling the interrupt, in 
case there is a pending interrupt.  This just happened to me in testing, 
so I recommend this:

> 	/*
> 	 * Get the frequency of system counter from the cp15 interface of ARM
> 	 * Generic timer. We don't need to check it, because if it returns "0",
> 	 * system would panic in very early stage.
> 	 */
> 	gwdt->clk = arch_timer_get_cntfrq();
> 	gwdt->refresh_base = rf_base;
> 	gwdt->control_base = cf_base;
>
> 	if (action) {
> 		irq = platform_get_irq(pdev, 0);
> 		if (irq < 0) {
> 			action = 0;
> 			dev_warn(dev, "unable to get ws0 interrupt.\n");
> 		} else {
> 			sbsa_gwdt_keepalive(&gwdt->wdd);
> 			if (devm_request_irq(dev, irq, sbsa_gwdt_interrupt, 0,
> 					     pdev->name, gwdt)) {
> 				action = 0;
> 				dev_warn(dev, "unable to request IRQ %d.\n",
> 					 irq);
> 			}
> 		}
> 		if (!action)
> 			dev_warn(dev, "falling back to single stage mode.\n");
> 	}

In fact, I think you need to move the "if (action) {" block near the end 
of sbsa_gwdt_probe().  We don't want to enable the interrupt until the 
watchdog is fully initialized.

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