linux-kernel - Re: [PATCHv2] mmc: append a file to change host clock at run time

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Date:	Thu, 14 Oct 2010 02:57:26 +0100
From:	Chris Ball <cjb@...top.org>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Adrian Hunter <adrian.hunter@...ia.com>,
	Andy Shevchenko <ext-andriy.shevchenko@...ia.com>
Subject: Re: [PATCHv2] mmc: append a file to change host clock at run time

Hi Andy,

On Wed, Oct 13, 2010 at 11:22:22AM +0300, Andy Shevchenko wrote:
> For debugging power managment features there is quite convenient to have a
> possibility to change MMC host controller clock at run time. This patch adds
> 'clock' file under MMC host root of debugfs.
> 
> Usage as follows:
> 
> 	# cat /sys/kernel/debug/mmc0/clock
> 	52000000
> 
> 	# echo "1000000000" > /sys/kernel/debug/mmc0/clock
> 	# cat /sys/kernel/debug/mmc0/clock
> 	52000000
> 
> 	# echo "48000000" > /sys/kernel/debug/mmc0/clock
> 	# cat /sys/kernel/debug/mmc0/clock
> 	48000000
> 
> The second piece of example shows limits which are applied accordingly to used
> host driver.
> 
> Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@...ia.com>
> ---
>  drivers/mmc/core/debugfs.c |   35 +++++++++++++++++++++++++++++++++--
>  1 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
> index 96d10f4..9b6ec07 100644
> --- a/drivers/mmc/core/debugfs.c
> +++ b/drivers/mmc/core/debugfs.c
> @@ -133,6 +133,33 @@ static const struct file_operations mmc_ios_fops = {
>  	.release	= single_release,
>  };
>  
> +static int mmc_clock_opt_get(void *data, u64 *val)
> +{
> +	struct mmc_host *host = data;
> +
> +	*val = host->ios.clock;
> +
> +	return 0;
> +}
> +
> +static int mmc_clock_opt_set(void *data, u64 val)
> +{
> +	struct mmc_host *host = data;
> +
> +	/* We need this check due to input value is u64 */
> +	if (val > host->f_max)
> +		return -EINVAL;
> +
> +	mmc_claim_host(host);
> +	mmc_set_clock(host, (unsigned int) val);
> +	mmc_release_host(host);
> +
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(mmc_clock_fops, mmc_clock_opt_get, mmc_clock_opt_set,
> +	"%llu\n");
> +
>  void mmc_add_host_debugfs(struct mmc_host *host)
>  {
>  	struct dentry *root;
> @@ -149,11 +176,15 @@ void mmc_add_host_debugfs(struct mmc_host *host)
>  	host->debugfs_root = root;
>  
>  	if (!debugfs_create_file("ios", S_IRUSR, root, host, &mmc_ios_fops))
> -		goto err_ios;
> +		goto err_node;
> +
> +	if (!debugfs_create_file("clock", S_IRUSR | S_IWUSR, root, host,
> +			&mmc_clock_fops))
> +		goto err_node;
>  
>  	return;
>  
> -err_ios:
> +err_node:
>  	debugfs_remove_recursive(root);
>  	host->debugfs_root = NULL;
>  err_root:
> -- 

Thanks, looks good -- applied to mmc-next with minor changelog edits.

-- 
Chris Ball   <cjb@...top.org>   <http://printf.net/>
One Laptop Per Child
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