linux-kernel - Re: [PATCH v4 2/2] watchdog: Add Renesas RZ/N1 Watchdog driver

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Date:   Thu, 31 Mar 2022 14:08:51 +0800
From:   Tzung-Bi Shih <tzungbi@...nel.org>
To:     Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Cc:     wim@...ux-watchdog.org, linux@...ck-us.net,
        geert+renesas@...der.be, linux-watchdog@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Phil Edworthy <phil.edworthy@...esas.com>
Subject: Re: [PATCH v4 2/2] watchdog: Add Renesas RZ/N1 Watchdog driver

On Wed, Mar 30, 2022 at 12:08:29PM +0200, Jean-Jacques Hiblot wrote:
> diff --git a/drivers/watchdog/rzn1_wdt.c b/drivers/watchdog/rzn1_wdt.c
[...]
> +/*
> + * Renesas RZ/N1 Watchdog timer.
> + * This is a 12-bit timer driver from a (62.5/16384) MHz clock. It can't even
> + * cope with 2 seconds.
> + *
> + * Copyright 2018 Renesas Electronics Europe Ltd.

s/2018/2022/ ?

> +#define RZN1_WDT_RETRIGGER			0x0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL		0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL_MASK	0xfff
> +#define RZN1_WDT_RETRIGGER_PRESCALE		BIT(12)
> +#define RZN1_WDT_RETRIGGER_ENABLE		BIT(13)
> +#define RZN1_WDT_RETRIGGER_WDSI			(0x2 << 14)

Do RZN1_WDT_RETRIGGER_RELOAD_VAL and RZN1_WDT_RETRIGGER_WDSI get 1 more tab
indent intentionally?

> +static const struct watchdog_device rzn1_wdt = {
> +	.info = &rzn1_wdt_info,
> +	.ops = &rzn1_wdt_ops,
> +	.status = WATCHDOG_NOWAYOUT_INIT_STATUS,
> +};
[...]
> +static int rzn1_wdt_probe(struct platform_device *pdev)
> +{
[...]
> +	wdt->wdt = rzn1_wdt;

Does it really need to copy the memory?  For example,

1. Use the memory in `wdt` directly and fill the `wdd`.

struct watchdog_device *wdd = &wdt->wdt;
wdd->info = &rzn1_wdt_info;
wdd->ops = &rzn1_wdt_ops;
...

2. Use drvdata instead of container_of().

Use watchdog_set_drvdata() in _probe and watchdog_get_drvdata() in the
watchdog ops to get struct rzn1_watchdog.

> +static const struct of_device_id rzn1_wdt_match[] = {
> +	{ .compatible = "renesas,rzn1-wdt" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, rzn1_wdt_match);

Doesn't it need to guard by CONFIG_OF?

> +static struct platform_driver rzn1_wdt_driver = {
> +	.probe		= rzn1_wdt_probe,
> +	.driver		= {
> +		.name		= KBUILD_MODNAME,
> +		.of_match_table	= rzn1_wdt_match,

Does it makes more sense to use of_match_ptr()?

> +	},
> +};
> +
> +module_platform_driver(rzn1_wdt_driver);

To make it look like a whole thing, I prefer to remove the extra blank line
in between struct platform_driver and module_platform_driver().