mmc: add a file to debugfs for changing host clock at runtime (703aae3d) · Commits · 戴 / test

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>

drivers/mmc/core/debugfs.c

+33 −2

Original line number	Diff line number	Diff line
		@@ -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:

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