linux-kernel - Re: [PATCH 1/9] watchdog: of_xilinx

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Date:   Thu, 16 Jan 2020 07:48:15 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Srinivas Neeli <srinivas.neeli@...inx.com>
Cc:     michal.simek@...inx.com, shubhrajyoti.datta@...inx.com,
        sgoud@...inx.com, wim@...ux-watchdog.org,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        git@...inx.com
Subject: Re: [PATCH 1/9] watchdog: of_xilinx_wdt: Add comment to spinlock

On Thu, Jan 16, 2020 at 06:56:49PM +0530, Srinivas Neeli wrote:
> From: Srinivas Goud <srinivas.goud@...inx.com>
> 
> Based on checkpatch every spinlock should be documented.
> The patch is fixing this issue:
> ./scripts/checkpatch.pl --strict -f drivers/watchdog/of_xilinx_wdt.c
> CHECK: spinlock_t definition without comment
> +	spinlock_t spinlock;

One of the most useless feedback messages from checkpatch.

> 
> Signed-off-by: Srinivas Goud <srinivas.goud@...inx.com>
> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> ---
>  drivers/watchdog/of_xilinx_wdt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/of_xilinx_wdt.c b/drivers/watchdog/of_xilinx_wdt.c
> index 7fe4f7c3f7ce..00549164b3d7 100644
> --- a/drivers/watchdog/of_xilinx_wdt.c
> +++ b/drivers/watchdog/of_xilinx_wdt.c
> @@ -40,7 +40,7 @@
>  struct xwdt_device {
>  	void __iomem *base;
>  	u32 wdt_interval;
> -	spinlock_t spinlock;
> +	spinlock_t spinlock; /* spinlock for register handling */

I don't see the added value here. Besides, what does the lock actually do ?
Watchdog drivers are single-open, so it seems quite difficult for any
of the protected functions to be called multiple times. The spinlock doesn't
disable interrupts, so register accesses by other drivers are still possible.
What am I missing ?

Guenter

>  	struct watchdog_device xilinx_wdt_wdd;
>  	struct clk		*clk;
>  };
> -- 
> 2.7.4
>