linux-kernel - Re: [PATCH 3/4] watchdog: sa11x0/pxa: get rid of get_clock_tick

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Date:   Mon, 19 Sep 2016 13:08:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wim Van Sebroeck <wim@...ana.be>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH 3/4] watchdog: sa11x0/pxa: get rid of get_clock_tick_rate

On Mon, Sep 19, 2016 at 09:12:14PM +0200, Robert Jarzmik wrote:
> The OS timer rate used for the watchdog can now be fetched from the
> standard clock API. This will remove the last user of
> get_clock_tick_rate() in both pxa and sa11x0 architectures.
> 
> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>

Did you test this ? Potential problem, if built into the kernel, could be that
the clocks might not be ready by the time the driver is instantiated. Unless
this is converted to a platform driver, it won't be able to handle a
-EPROBE_DEFER from the clock subsystem.

Guenter

> ---
>  drivers/watchdog/sa1100_wdt.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/sa1100_wdt.c b/drivers/watchdog/sa1100_wdt.c
> index e1d39a1e9628..8965e3f536c3 100644
> --- a/drivers/watchdog/sa1100_wdt.c
> +++ b/drivers/watchdog/sa1100_wdt.c
> @@ -22,6 +22,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/moduleparam.h>
> +#include <linux/clk.h>
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/fs.h>
> @@ -155,12 +156,27 @@ static struct miscdevice sa1100dog_miscdev = {
>  };
>  
>  static int margin __initdata = 60;		/* (secs) Default is 1 minute */
> +static struct clk *clk;
>  
>  static int __init sa1100dog_init(void)
>  {
>  	int ret;
>  
> -	oscr_freq = get_clock_tick_rate();
> +	clk = clk_get(NULL, "OSTIMER0");
> +	if (IS_ERR(clk)) {
> +		pr_err("SA1100/PXA2xx Watchdog Timer: clock not found: %d\n",
> +		       (int) PTR_ERR(clk));
> +		return PTR_ERR(clk);
> +	}
> +
> +	ret = clk_prepare_enable(clk);
> +	if (ret) {
> +		pr_err("SA1100/PXA2xx Watchdog Timer: clock failed to prepare+enable: %d\n",
> +		       ret);
> +		goto err;
> +	}
> +
> +	oscr_freq = clk_get_rate(clk);
>  
>  	/*
>  	 * Read the reset status, and save it for later.  If
> @@ -176,11 +192,17 @@ static int __init sa1100dog_init(void)
>  		pr_info("SA1100/PXA2xx Watchdog Timer: timer margin %d sec\n",
>  			margin);
>  	return ret;
> +err:
> +	clk_disable_unprepare(clk);
> +	clk_put(clk);
> +	return ret;
>  }
>  
>  static void __exit sa1100dog_exit(void)
>  {
>  	misc_deregister(&sa1100dog_miscdev);
> +	clk_disable_unprepare(clk);
> +	clk_put(clk);
>  }
>  
>  module_init(sa1100dog_init);
> -- 
> 2.1.4
> 
> --
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