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mmc: add a file to debugfs for changing host clock at runtime

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For debugging power management features it is convenient to have the
possibility of changing the MMC host controller clock at runtime.  This
patch adds a 'clock' file for this under the MMC host root of debugfs.

Usage is 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 middle example shows limits being applied by the host driver.

Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Cc: Adrian Hunter <adrian.hunter@nokia.com>
[cjb: modify changelog language]
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Andy Shevchenko 2010-10-13 11:22:22 +03:00 committed by Chris Ball
parent 643a81ff3c
commit 703aae3d09
1 changed files with 33 additions and 2 deletions
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35
drivers/mmc/core/debugfs.c
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@ -134,6 +134,33 @@ 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;
@ -150,11 +177,15 @@ 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: