[PATCH RFC 7/7] mmc: core: Add a debugfs entry to set max clock rate
From: Sayali Lokhande <hidden>
Date: 2018-07-13 09:54:27
Also in:
linux-arm-msm, linux-mmc, lkml
Subsystem:
multimedia card (mmc), secure digital (sd) and sdio subsystem, the rest · Maintainers:
Ulf Hansson, Linus Torvalds
Limiting the max frequency supported by host controller to a certain value can be useful for testing power consumption at various frequencies that are supported by the host. Note: If the card supports less than desired value then the frequency of operation would be limited to that frequency. Usage: mount -t debugfs none /sys/kernel/debug echo <desired_frequency> > /sys/kernel/debug/mmcX/max_clock cat /sys/kernel/debug/mmcX/max_clock Signed-off-by: Sujit Reddy Thumma <redacted> Signed-off-by: Sayali Lokhande <redacted> --- drivers/mmc/core/debugfs.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)
diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index 630ca8e..26499f7 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c@@ -262,6 +262,46 @@ static int mmc_scale_set(void *data, u64 val) DEFINE_SIMPLE_ATTRIBUTE(mmc_scale_fops, mmc_scale_get, mmc_scale_set, "%llu\n"); +static int mmc_max_clock_get(void *data, u64 *val) +{ + struct mmc_host *host = data; + + if (!host) + return -EINVAL; + + *val = host->f_max; + + return 0; +} + +static int mmc_max_clock_set(void *data, u64 val) +{ + struct mmc_host *host = data; + int err = -EINVAL; + unsigned long freq = val; + unsigned int old_freq; + + if (!host || (val < host->f_min)) + goto out; + + mmc_claim_host(host); + if (host->bus_ops && host->bus_ops->change_bus_speed) { + old_freq = host->f_max; + host->f_max = freq; + + err = host->bus_ops->change_bus_speed(host, &freq); + + if (err) + host->f_max = old_freq; + } + mmc_release_host(host); +out: + return err; +} + +DEFINE_SIMPLE_ATTRIBUTE(mmc_max_clock_fops, mmc_max_clock_get, + mmc_max_clock_set, "%llu\n"); + void mmc_add_host_debugfs(struct mmc_host *host) { struct dentry *root;
@@ -290,6 +330,10 @@ void mmc_add_host_debugfs(struct mmc_host *host) &mmc_clock_fops)) goto err_node; + if (!debugfs_create_file("max_clock", 0600, root, host, + &mmc_max_clock_fops)) + goto err_node; + if (!debugfs_create_file("scale", 0600, root, host, &mmc_scale_fops)) goto err_node;
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