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

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Date:   Thu, 31 Mar 2022 19:26:50 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Tzung-Bi Shih <tzungbi@...nel.org>,
        Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Cc:     wim@...ux-watchdog.org, 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 3/30/22 23:08, Tzung-Bi Shih wrote:
> 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?
> 

That only looks like it due to the "+" at the beginning of the line.
If you look at the actual code the alignment is ok.

>> +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.
> 
That would indeed be preferred. The static data structure isn't really useful.

>> +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?
> 
Only if of_match_ptr() is used below, and then I'd prefer __maybe_unused

>> +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()?
> 

Usually we leave that up to driver authors.

>> +	},
>> +};
>> +
>> +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().

We usually leave that up to driver authors. Many watchdog driver leave
an empty line, so it is ok (as long as there are no two empty lines).

Thanks,
Guenter