linux-kernel - Re: [PATCH v10 4/5] watchdog: Add RAVE SP watchdog driver

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Date:   Sun, 5 Nov 2017 16:47:25 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
        cphealy@...il.com, Lucas Stach <l.stach@...gutronix.de>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Lee Jones <lee.jones@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Rob Herring <robh@...nel.org>, Johan Hovold <johan@...nel.org>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Subject: Re: [PATCH v10 4/5] watchdog: Add RAVE SP watchdog driver

On Tue, Oct 31, 2017 at 09:36:55AM -0700, Andrey Smirnov wrote:
> This driver provides access to RAVE SP watchdog functionality.
> 
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-watchdog@...r.kernel.org
> Cc: cphealy@...il.com
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: Nikita Yushchenko <nikita.yoush@...entembedded.com>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Andy Shevchenko <andy.shevchenko@...il.com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Johan Hovold <johan@...nel.org>
> Cc: Sebastian Reichel <sebastian.reichel@...labora.co.uk>
> Signed-off-by: Nikita Yushchenko <nikita.yoush@...entembedded.com>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>

> +static const struct of_device_id rave_sp_wdt_of_match[] = {
> +	{ .compatible = "zii,rave-sp-watchdog" },
> +	{}
> +};

> +static const struct of_device_id rave_sp_wdt_variants[] = {
> +	{ .compatible = COMPATIBLE_RAVE_SP_NIU,  .data = &rave_sp_wdt_legacy },
> +	{ .compatible = COMPATIBLE_RAVE_SP_MEZZ, .data = &rave_sp_wdt_legacy },
> +	{ .compatible = COMPATIBLE_RAVE_SP_ESB,  .data = &rave_sp_wdt_legacy },
> +	{ .compatible = COMPATIBLE_RAVE_SP_RDU1, .data = &rave_sp_wdt_rdu    },
> +	{ .compatible = COMPATIBLE_RAVE_SP_RDU2, .data = &rave_sp_wdt_rdu    },
> +	{ /* sentinel */ }
> +};
> +
> +static int rave_sp_wdt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	const struct of_device_id *id;
> +	struct watchdog_device *wdd;
> +	struct rave_sp_wdt *sp_wd;
> +	struct nvmem_cell *cell;
> +	__le16 timeout = 0;
> +	int ret;
> +
> +	id = of_match_device(rave_sp_wdt_variants, dev->parent);

So as I already mentioned in a comment on an earlier version of the MFD
driver, I find this matching on the parent of_node to be an odd
pattern, which also does not seem to have any precedent in mainline.  

It seems you really should be using two compatible strings for the
watchdog (for the legacy and rdu variants) rather than keep an entry for
every parent compatible-string in every child/cell driver (which all
need to be kept in sync).

But let's see what Rob and Lee says about this.

> +	if (!id) {
> +		dev_err(dev, "Unknown parent device variant. Bailing out\n");
> +		return -ENODEV;
> +	}
> +
> +	sp_wd = devm_kzalloc(dev, sizeof(*sp_wd), GFP_KERNEL);
> +	if (!sp_wd)
> +		return -ENOMEM;
> +
> +	sp_wd->variant = id->data;
> +	sp_wd->sp      = dev_get_drvdata(dev->parent);
> +
> +	wdd              = &sp_wd->wdd;
> +	wdd->parent      = dev;
> +	wdd->info        = &rave_sp_wdt_info;
> +	wdd->ops         = &rave_sp_wdt_ops;
> +	wdd->min_timeout = sp_wd->variant->min_timeout;
> +	wdd->max_timeout = sp_wd->variant->max_timeout;
> +	wdd->status      = WATCHDOG_NOWAYOUT_INIT_STATUS;
> +	wdd->timeout     = 60;
> +
> +	cell = nvmem_cell_get(dev, "wdt-timeout");
> +	if (!IS_ERR(cell)) {
> +		size_t len;
> +		void *value = nvmem_cell_read(cell, &len);
> +
> +		if (!IS_ERR(value)) {
> +			memcpy(&timeout, value, min(len, sizeof(timeout)));
> +			kfree(value);
> +		}
> +		nvmem_cell_put(cell);
> +	}
> +	watchdog_init_timeout(wdd, le16_to_cpu(timeout), dev);
> +	watchdog_set_restart_priority(wdd, 255);
> +
> +	sp_wd->reboot_notifier.notifier_call = rave_sp_wdt_reboot_notifier;
> +	ret = devm_register_reboot_notifier(dev, &sp_wd->reboot_notifier);
> +	if (ret) {
> +		dev_err(dev, "Failed to register reboot notifier\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * We don't know if watchdog is running now. To be sure, let's
> +	 * start it and depend on watchdog core to ping it
> +	 */
> +	wdd->max_hw_heartbeat_ms = wdd->max_timeout * 1000;
> +	ret = rave_sp_wdt_start(wdd);
> +	if (ret) {
> +		dev_err(dev, "Watchdog didn't start\n");
> +		return ret;
> +	}
> +
> +	return devm_watchdog_register_device(dev, wdd);

What about stopping the watchdog on errors here?

And does watchdog core take care of calling stop() on unregister (i.e.
at unbind)?

> +}
> +
> +static struct platform_driver rave_sp_wdt_driver = {
> +	.probe = rave_sp_wdt_probe,
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +		.of_match_table = rave_sp_wdt_of_match,
> +	},
> +};

Johan