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

[Guenter Roeck]

On 11/05/2017 07:47 AM, Johan Hovold wrote:
> 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@xxxxxxxxxxxxxxx
> > Cc: linux-watchdog@xxxxxxxxxxxxxxx
> > Cc: cphealy@xxxxxxxxx
> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > Cc: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
> > Cc: Lee Jones <lee.jones@xxxxxxxxxx>
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Pavel Machek <pavel@xxxxxx>
> > Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> > Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Cc: Rob Herring <robh@xxxxxxxxxx>
> > Cc: Johan Hovold <johan@xxxxxxxxxx>
> > Cc: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
> > Signed-off-by: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
>
> > +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)?
Both good points. This needs watchdog_stop_on_unregister(), and the
probe function needs to stop the watchdog if registration fails.

Guenter

> > +}
> > +
> > +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
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