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Date: Wed, 19 Nov 2014 12:36:06 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
cc: "H . Peter Anvin" <hpa@linux.intel.com>, x86@kernel.org,
        Aubrey Li <aubrey.li@linux.intel.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        "Kumar P, Mahesh" <mahesh.kumar.p@intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/3] x86: pmc_atom: don't check for NULL twice
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On Wed, 12 Nov 2014, Andy Shevchenko wrote:

> debugfs_remove_recursive() is NULL-aware, thus, we may safely remove the check
> here. There is no need to assing NULL to variable since it will be not used
> anywhere.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Acked-by: Aubrey Li <aubrey.li@linux.intel.com>
> ---
>  arch/x86/kernel/pmc_atom.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/pmc_atom.c b/arch/x86/kernel/pmc_atom.c
> index 19b8efa..bcc91ea 100644
> --- a/arch/x86/kernel/pmc_atom.c
> +++ b/arch/x86/kernel/pmc_atom.c
> @@ -202,11 +202,7 @@ static const struct file_operations pmc_sleep_tmr_ops = {
>  
>  static void pmc_dbgfs_unregister(struct pmc_dev *pmc)
>  {
> -	if (!pmc->dbgfs_dir)
> -		return;
> -
>  	debugfs_remove_recursive(pmc->dbgfs_dir);
> -	pmc->dbgfs_dir = NULL;
>  }

So while the patch is correct per se, the whole function is useless.

pmc_dbgfs_register()

	dir = debugfs_create_dir("pmc_atom", NULL);

	....
	if (!f)
		goto err;

	pmc->dbgfs_dir = dir;
	return 0;
err:
	pmc_dbgfs_unregister(pmc);

So pmc->dbgfs_dir is always NULL when this is called....

Aside of that, if DEBUGFS=n the code keeps pmc->regmap ioremapped for
no reason.

Looking deeper:

The pmc_power_off function is installed _BEFORE_ pmc_hw_reg_setup() is
called, which might not be called if the ioremap fails ....

Thanks,

	tglx