linux-kernel - Re: [PATCH 4/4] watchdog: aspeed: Move init to arch

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Date:   Mon, 18 Sep 2017 06:32:46 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Jeffery <andrew@...id.au>, linux-watchdog@...r.kernel.org
Cc:     wim@...ana.be, joel@....id.au, linux-kernel@...r.kernel.org,
        openbmc@...ts.ozlabs.org, linux-aspeed@...ts.ozlabs.org,
        ryan_chen@...eedtech.com
Subject: Re: [PATCH 4/4] watchdog: aspeed: Move init to arch_initcall

On 09/17/2017 10:49 PM, Andrew Jeffery wrote:
> Probing at device_initcall time lead to perverse cases where the
> watchdog was probed after, say, I2C, which then leaves a potentially
> running watchdog at the mercy of I2C device behaviour and bus
> conditions.
> 
> Load the watchdog driver early to ensure that the kernel is patting it
> well before initialising peripherals.
> 
But you are doing a bit more. You are making it bool, and you are enabling it
by default. Both isn't needed for the intended goal (arch_initcall is converted
to module_initcall if a driver is built as module). Your change focuses on
and optimizes the case where the watchdog is already running. That may not
always be the case, and there may be systems where the driver is not loaded
on purpose.

Guenter

> Signed-off-by: Andrew Jeffery <andrew@...id.au>
> ---
>   drivers/watchdog/Kconfig      | 6 ++----
>   drivers/watchdog/aspeed_wdt.c | 7 ++++++-
>   2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index a1b92ebe74b6..6103185983ed 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -741,8 +741,9 @@ config RENESAS_RZAWDT
>   	  Renesas RZ/A SoCs. These watchdogs can be used to reset a system.
>   
>   config ASPEED_WATCHDOG
> -	tristate "Aspeed BMC watchdog support"
> +	bool "Aspeed BMC watchdog support"
>   	depends on ARCH_ASPEED || COMPILE_TEST
> +	default y if ARCH_ASPEED
>   	select WATCHDOG_CORE
>   	help
>   	  Say Y here to include support for the watchdog timer
> @@ -750,9 +751,6 @@ config ASPEED_WATCHDOG
>   
>   	  This driver is required to reboot the SoC.
>   
> -	  To compile this driver as a module, choose M here: the
> -	  module will be called aspeed_wdt.
> -
>   config ZX2967_WATCHDOG
>   	tristate "ZTE zx2967 SoCs watchdog support"
>   	depends on ARCH_ZX
> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
> index 99bc6fbd8852..679c35abadc4 100644
> --- a/drivers/watchdog/aspeed_wdt.c
> +++ b/drivers/watchdog/aspeed_wdt.c
> @@ -313,7 +313,12 @@ static struct platform_driver aspeed_watchdog_driver = {
>   		.of_match_table = of_match_ptr(aspeed_wdt_of_table),
>   	},
>   };
> -module_platform_driver(aspeed_watchdog_driver);
> +
> +static int __init aspeed_wdt_init(void)
> +{
> +	return platform_driver_register(&aspeed_watchdog_driver);
> +}
> +arch_initcall(aspeed_wdt_init);
>   
>   MODULE_DESCRIPTION("Aspeed Watchdog Driver");
>   MODULE_LICENSE("GPL");
>