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Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <1cb7fdb7-ebad-a61e-490c-80e6c9feab2b@roeck-us.net>
Date:   Sun, 2 Oct 2022 09:29:32 -0700
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Subject: Re: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal window watchdog
 support
Content-Language: en-US
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Srinivas Neeli <srinivas.neeli@amd.com>,
        wim@linux-watchdog.org, shubhrajyoti.datta@amd.com,
        michal.simek@amd.com, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org
Cc:     linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        git@amd.com
References: <20220927110257.41963-1-srinivas.neeli@amd.com>
 <20220927110257.41963-3-srinivas.neeli@amd.com>
 <c1e34c50-50ac-0e06-3af7-a1eec886bf07@linaro.org>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <c1e34c50-50ac-0e06-3af7-a1eec886bf07@linaro.org>
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Precedence: bulk

On 9/30/22 03:35, Krzysztof Kozlowski wrote:
> On 27/09/2022 13:02, Srinivas Neeli wrote:
>> +
>> +static void xwwdt_clk_disable_unprepare(void *data)
>> +{
>> +	clk_disable_unprepare(data);
> 
> If watchdog is stopped and then device unbound, don't you have double
> disable? IOW, where is matching clk_enable?
> 

After looking into the entire driver code, I see the problem:
clk_disable() is called in the stop function. That is wrong;
if the clock is disabled in the stop function, it needs to be
enabled in the start function (which is not currently the case).
In that situation, using the devm_ callback when unloading the
driver isn't possible (or, rather, would require checking if the
clock is enabled before disabling it).

Thanks,
Guenter

>> +}
>> +
>> +static const struct watchdog_info xilinx_wwdt_ident = {
>> +	.options = WDIOF_KEEPALIVEPING |
>> +		WDIOF_SETTIMEOUT,
>> +	.firmware_version = 1,
>> +	.identity = "xlnx_window watchdog",
>> +};
>> +
>> +static const struct watchdog_ops xilinx_wwdt_ops = {
>> +	.owner = THIS_MODULE,
>> +	.start = xilinx_wwdt_start,
>> +	.stop = xilinx_wwdt_stop,
>> +	.set_timeout = xilinx_wwdt_set_timeout,
>> +	.ping = xilinx_wwdt_keepalive,
>> +};
>> +
>> +static int xwwdt_probe(struct platform_device *pdev)
>> +{
>> +	struct watchdog_device *xilinx_wwdt_wdd;
>> +	struct device *dev = &pdev->dev;
>> +	struct xwwdt_device *xdev;
>> +	int ret;
>> +
>> +	xdev = devm_kzalloc(dev, sizeof(*xdev), GFP_KERNEL);
>> +	if (!xdev)
>> +		return -ENOMEM;
>> +
>> +	xilinx_wwdt_wdd = &xdev->xilinx_wwdt_wdd;
>> +	xilinx_wwdt_wdd->info = &xilinx_wwdt_ident;
>> +	xilinx_wwdt_wdd->ops = &xilinx_wwdt_ops;
>> +	xilinx_wwdt_wdd->parent = dev;
>> +
>> +	xdev->base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(xdev->base))
>> +		return PTR_ERR(xdev->base);
>> +
>> +	xdev->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(xdev->clk))
>> +		return PTR_ERR(xdev->clk);
>> +
>> +	xdev->freq = clk_get_rate(xdev->clk);
>> +	if (!xdev->freq)
>> +		return -EINVAL;
>> +
>> +	ret = clk_prepare_enable(xdev->clk);
>> +	if (ret) {
>> +		dev_err(dev, "unable to enable clock\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = devm_add_action_or_reset(dev, xwwdt_clk_disable_unprepare,
>> +				       xdev->clk);
>> +	if (ret)
>> +		return ret;
>> +
>> +	xilinx_wwdt_wdd->timeout = XWWDT_DEFAULT_TIMEOUT;
>> +	xilinx_wwdt_wdd->min_timeout = XWWDT_MIN_TIMEOUT;
>> +	xilinx_wwdt_wdd->max_timeout = XWWDT_MAX_TIMEOUT;
>> +
>> +	ret = watchdog_init_timeout(xilinx_wwdt_wdd,
>> +				    xwwdt_timeout, &pdev->dev);
>> +	if (ret)
>> +		dev_info(&pdev->dev, "Configured default timeout value\n");
>> +
>> +	spin_lock_init(&xdev->spinlock);
>> +	watchdog_set_drvdata(xilinx_wwdt_wdd, xdev);
>> +
>> +	ret = devm_watchdog_register_device(dev, xilinx_wwdt_wdd);
>> +	if (ret)
>> +		return ret;
>> +
>> +	dev_info(dev, "Xilinx window watchdog Timer with timeout %ds\n",
>> +		 xilinx_wwdt_wdd->timeout);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id xwwdt_of_match[] = {
>> +	{ .compatible = "xlnx,versal-wwdt-1.0", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, xwwdt_of_match);
>> +
>> +static struct platform_driver xwwdt_driver = {
>> +	.probe = xwwdt_probe,
>> +	.driver = {
>> +		.name = "Xilinx window watchdog",
> 
> Do you see spaces in other names of drivers?
> 
> Best regards,
> Krzysztof
>