[V1,2/7] mmc: core: devfreq: Add devfreq based clock scaling support

Message ID 1539003486-24087-3-git-send-email-sayalil@codeaurora.org
State Changes Requested
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Series
  • Add devfreq based clock scaling support for mmc
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Commit Message

Sayali Lokhande Oct. 8, 2018, 12:58 p.m.
This change adds the use of devfreq to MMC.
Both eMMC and SD card will use it.
For some workloads, such as video playback, it isn't
necessary for these cards to run at high speed.
Running at lower frequency, for example 52MHz, in such
cases can still meet the deadlines for data transfers.
Scaling down the clock frequency dynamically has power
savings not only because the bus is running at lower frequency
but also has an advantage of scaling down the system core
voltage, if supported.
Provide an ondemand clock scaling support similar to the
cpufreq ondemand governor having two thresholds,
up_threshold and down_threshold to decide whether to
increase the frequency or scale it down respectively.
The sampling interval is in the order of milliseconds.
If sampling interval is too low, frequent switching of
frequencies can lead to high power consumption and if
sampling interval is too high, the clock scaling logic
would take long time to realize that the underlying
hardware (controller and card) is busy and scale up
the clocks.

Signed-off-by: Talel Shenhar <tatias@codeaurora.org>
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
---
 .../devicetree/bindings/mmc/sdhci-msm.txt          |  10 +
 drivers/mmc/core/core.c                            | 556 +++++++++++++++++++++
 drivers/mmc/core/core.h                            |   7 +
 drivers/mmc/core/debugfs.c                         |  46 ++
 drivers/mmc/core/host.c                            |   8 +
 drivers/mmc/core/mmc.c                             | 200 +++++++-
 drivers/mmc/core/sd.c                              |  72 ++-
 drivers/mmc/host/sdhci-msm.c                       |  37 ++
 drivers/mmc/host/sdhci-pltfm.c                     |  11 +
 drivers/mmc/host/sdhci.c                           |  27 +
 drivers/mmc/host/sdhci.h                           |   8 +
 include/linux/mmc/card.h                           |   5 +
 include/linux/mmc/host.h                           |  70 +++
 13 files changed, 1055 insertions(+), 2 deletions(-)

Comments

Rob Herring Oct. 17, 2018, 2:04 p.m. | #1
On Mon, Oct 08, 2018 at 06:28:01PM +0530, Sayali Lokhande wrote:
> This change adds the use of devfreq to MMC.
> Both eMMC and SD card will use it.
> For some workloads, such as video playback, it isn't
> necessary for these cards to run at high speed.
> Running at lower frequency, for example 52MHz, in such
> cases can still meet the deadlines for data transfers.
> Scaling down the clock frequency dynamically has power
> savings not only because the bus is running at lower frequency
> but also has an advantage of scaling down the system core
> voltage, if supported.

Is there really power savings if there's no voltage control?

> Provide an ondemand clock scaling support similar to the
> cpufreq ondemand governor having two thresholds,
> up_threshold and down_threshold to decide whether to
> increase the frequency or scale it down respectively.
> The sampling interval is in the order of milliseconds.
> If sampling interval is too low, frequent switching of
> frequencies can lead to high power consumption and if
> sampling interval is too high, the clock scaling logic
> would take long time to realize that the underlying
> hardware (controller and card) is busy and scale up
> the clocks.

Why the short lines?

> 
> Signed-off-by: Talel Shenhar <tatias@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>  .../devicetree/bindings/mmc/sdhci-msm.txt          |  10 +

Bindings should be separate patches.

>  drivers/mmc/core/core.c                            | 556 +++++++++++++++++++++
>  drivers/mmc/core/core.h                            |   7 +
>  drivers/mmc/core/debugfs.c                         |  46 ++
>  drivers/mmc/core/host.c                            |   8 +
>  drivers/mmc/core/mmc.c                             | 200 +++++++-
>  drivers/mmc/core/sd.c                              |  72 ++-
>  drivers/mmc/host/sdhci-msm.c                       |  37 ++
>  drivers/mmc/host/sdhci-pltfm.c                     |  11 +
>  drivers/mmc/host/sdhci.c                           |  27 +
>  drivers/mmc/host/sdhci.h                           |   8 +
>  include/linux/mmc/card.h                           |   5 +
>  include/linux/mmc/host.h                           |  70 +++
>  13 files changed, 1055 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> index 502b3b8..bd8470a 100644
> --- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> +++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> @@ -26,6 +26,15 @@ Required properties:
>  	"cal"	- reference clock for RCLK delay calibration (optional)
>  	"sleep"	- sleep clock for RCLK delay calibration (optional)
>  
> +Optional Properties:
> +- qcom,devfreq,freq-table - specifies supported frequencies for clock scaling.
> +				    Clock scaling logic shall toggle between these frequencies based
> +				    on card load. In case the defined frequencies are over or below
> +				    the supported card frequencies, they will be overridden
> +				    during card init. In case this entry is not supplied,
> +				    the driver will construct one based on the card
> +				    supported max and min frequencies.
> +				    The frequencies must be ordered from lowest to highest.

Why is this qcom specific?

I believe I also saw interconnect binding for SD/MMC. How does that 
relate to this? There should be some coordination of this work.

>  Example:
>  
>  	sdhc_1: sdhci@f9824900 {
> @@ -43,6 +52,7 @@ Example:
>  
>  		clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>;
>  		clock-names = "core", "iface";
> +		qcom,devfreq,freq-table = <52000000 200000000>;
>  	};
>  
>  	sdhc_2: sdhci@f98a4900 {

Patch

diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
index 502b3b8..bd8470a 100644
--- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
+++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
@@ -26,6 +26,15 @@  Required properties:
 	"cal"	- reference clock for RCLK delay calibration (optional)
 	"sleep"	- sleep clock for RCLK delay calibration (optional)
 
+Optional Properties:
+- qcom,devfreq,freq-table - specifies supported frequencies for clock scaling.
+				    Clock scaling logic shall toggle between these frequencies based
+				    on card load. In case the defined frequencies are over or below
+				    the supported card frequencies, they will be overridden
+				    during card init. In case this entry is not supplied,
+				    the driver will construct one based on the card
+				    supported max and min frequencies.
+				    The frequencies must be ordered from lowest to highest.
 Example:
 
 	sdhc_1: sdhci@f9824900 {
@@ -43,6 +52,7 @@  Example:
 
 		clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>;
 		clock-names = "core", "iface";
+		qcom,devfreq,freq-table = <52000000 200000000>;
 	};
 
 	sdhc_2: sdhci@f98a4900 {
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 281826d..a3d4a92 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -14,6 +14,7 @@ 
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/completion.h>
+#include <linux/devfreq.h>
 #include <linux/device.h>
 #include <linux/delay.h>
 #include <linux/pagemap.h>
@@ -112,6 +113,552 @@  static inline void mmc_should_fail_request(struct mmc_host *host,
 
 #endif /* CONFIG_FAIL_MMC_REQUEST */
 
+static bool mmc_is_data_request(struct mmc_request *mmc_request)
+{
+	switch (mmc_request->cmd->opcode) {
+	case MMC_READ_SINGLE_BLOCK:
+	case MMC_READ_MULTIPLE_BLOCK:
+	case MMC_WRITE_BLOCK:
+	case MMC_WRITE_MULTIPLE_BLOCK:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static void mmc_clk_scaling_start_busy(struct mmc_host *host, bool lock_needed)
+{
+	struct mmc_devfeq_clk_scaling *clk_scaling = &host->clk_scaling;
+
+	if (!clk_scaling->enable)
+		return;
+
+	if (lock_needed)
+		spin_lock_bh(&clk_scaling->lock);
+
+	clk_scaling->start_busy = ktime_get();
+	clk_scaling->is_busy_started = true;
+
+	if (lock_needed)
+		spin_unlock_bh(&clk_scaling->lock);
+}
+
+static void mmc_clk_scaling_stop_busy(struct mmc_host *host, bool lock_needed)
+{
+	struct mmc_devfeq_clk_scaling *clk_scaling = &host->clk_scaling;
+
+	if (!clk_scaling->enable)
+		return;
+
+	if (lock_needed)
+		spin_lock_bh(&clk_scaling->lock);
+
+	if (!clk_scaling->is_busy_started) {
+		WARN_ON(1);
+		goto out;
+	}
+
+	clk_scaling->total_busy_time_us +=
+		ktime_to_us(ktime_sub(ktime_get(),
+			clk_scaling->start_busy));
+	pr_debug("%s: accumulated busy time is %lu usec\n",
+		mmc_hostname(host), clk_scaling->total_busy_time_us);
+	clk_scaling->is_busy_started = false;
+
+out:
+	if (lock_needed)
+		spin_unlock_bh(&clk_scaling->lock);
+}
+
+/**
+ * mmc_can_scale_clk() - Check clock scaling capability
+ * @host: pointer to mmc host structure
+ */
+bool mmc_can_scale_clk(struct mmc_host *host)
+{
+	if (!host) {
+		pr_err("bad host parameter\n");
+		WARN_ON(1);
+		return false;
+	}
+
+	return host->caps2 & MMC_CAP2_CLK_SCALE;
+}
+EXPORT_SYMBOL(mmc_can_scale_clk);
+
+static int mmc_devfreq_get_dev_status(struct device *dev,
+		struct devfreq_dev_status *status)
+{
+	struct mmc_host *host = container_of(dev, struct mmc_host, class_dev);
+	struct mmc_devfeq_clk_scaling *clk_scaling;
+
+	if (!host) {
+		pr_err("bad host parameter\n");
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	clk_scaling = &host->clk_scaling;
+
+	if (!clk_scaling->enable)
+		return 0;
+
+	spin_lock_bh(&clk_scaling->lock);
+
+	/* accumulate the busy time of ongoing work */
+	memset(status, 0, sizeof(*status));
+	if (clk_scaling->is_busy_started) {
+			mmc_clk_scaling_stop_busy(host, false);
+			mmc_clk_scaling_start_busy(host, false);
+	}
+
+	status->busy_time = clk_scaling->total_busy_time_us;
+	status->total_time = ktime_to_us(ktime_sub(ktime_get(),
+		clk_scaling->measure_interval_start));
+	clk_scaling->total_busy_time_us = 0;
+	status->current_frequency = clk_scaling->curr_freq;
+	clk_scaling->measure_interval_start = ktime_get();
+
+	pr_debug("%s: status: load = %lu%% - total_time=%lu busy_time = %lu, clk=%lu\n",
+		mmc_hostname(host),
+		(status->busy_time*100)/status->total_time,
+		status->total_time, status->busy_time,
+		status->current_frequency);
+
+	spin_unlock_bh(&clk_scaling->lock);
+
+	return 0;
+}
+
+static bool mmc_is_valid_state_for_clk_scaling(struct mmc_host *host)
+{
+	struct mmc_card *card = host->card;
+	u32 status;
+
+	/*
+	 * If the current partition type is RPMB, clock switching may not
+	 * work properly as sending tuning command (CMD21) is illegal in
+	 * this mode.
+	 */
+	if (!card || (mmc_card_mmc(card) &&
+			(card->part_curr == EXT_CSD_PART_CONFIG_ACC_RPMB ||
+			mmc_card_doing_bkops(card))))
+		return false;
+
+	if (mmc_send_status(card, &status)) {
+		pr_err("%s: Get card status fail\n", mmc_hostname(card->host));
+		return false;
+	}
+
+	return R1_CURRENT_STATE(status) == R1_STATE_TRAN;
+}
+
+int mmc_clk_update_freq(struct mmc_host *host,
+		unsigned long freq, enum mmc_load state)
+{
+	int err = 0;
+
+	if (!host) {
+		pr_err("bad host parameter\n");
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	/* make sure the card supports the frequency we want */
+	if (unlikely(freq > host->card->clk_scaling_highest)) {
+		freq = host->card->clk_scaling_highest;
+		pr_warn("%s: %s: frequency was overridden to %lu\n",
+				mmc_hostname(host), __func__,
+				host->card->clk_scaling_highest);
+	}
+
+	if (unlikely(freq < host->card->clk_scaling_lowest)) {
+		freq = host->card->clk_scaling_lowest;
+		pr_warn("%s: %s: frequency was overridden to %lu\n",
+			mmc_hostname(host), __func__,
+			host->card->clk_scaling_lowest);
+	}
+
+	if (freq == host->clk_scaling.curr_freq)
+		goto out;
+
+	if (host->ops->notify_load) {
+		err = host->ops->notify_load(host, state);
+		if (err) {
+			pr_err("%s: %s: fail on notify_load\n",
+				mmc_hostname(host), __func__);
+			goto out;
+		}
+	}
+
+	if (!mmc_is_valid_state_for_clk_scaling(host)) {
+		pr_debug("%s: invalid state for clock scaling - skipping",
+			mmc_hostname(host));
+		goto invalid_state;
+	}
+
+	err = host->bus_ops->change_bus_speed(host, &freq);
+	if (!err)
+		host->clk_scaling.curr_freq = freq;
+	else
+		pr_err("%s: %s: failed (%d) at freq=%lu\n",
+			mmc_hostname(host), __func__, err, freq);
+
+invalid_state:
+	if (err) {
+		/* restore previous state */
+		if (host->ops->notify_load)
+			if (host->ops->notify_load(host,
+				host->clk_scaling.state))
+				pr_err("%s: %s: fail on notify_load restore\n",
+					mmc_hostname(host), __func__);
+	}
+out:
+	return err;
+}
+EXPORT_SYMBOL(mmc_clk_update_freq);
+
+static int mmc_devfreq_set_target(struct device *dev,
+				unsigned long *freq, u32 devfreq_flags)
+{
+	struct mmc_host *host = container_of(dev, struct mmc_host, class_dev);
+	struct mmc_devfeq_clk_scaling *clk_scaling;
+	int err = 0;
+	int abort;
+	unsigned long pflags = current->flags;
+
+	/* Ensure scaling would happen even in memory pressure conditions */
+	current->flags |= PF_MEMALLOC;
+
+	if (!(host && freq)) {
+		pr_err("%s: unexpected host/freq parameter\n", __func__);
+		err = -EINVAL;
+		goto out;
+	}
+
+	clk_scaling = &host->clk_scaling;
+
+	if (!clk_scaling->enable)
+		goto out;
+
+	pr_debug("%s: target freq = %lu (%s)\n", mmc_hostname(host),
+		*freq, current->comm);
+
+	/* No need to scale the clocks if they are gated */
+	if (!host->ios.clock)
+		goto out;
+
+	spin_lock_bh(&clk_scaling->lock);
+	if (clk_scaling->target_freq == *freq ||
+		clk_scaling->skip_clk_scale_freq_update ||
+		clk_scaling->clk_scaling_in_progress) {
+		spin_unlock_bh(&clk_scaling->lock);
+		goto out;
+	}
+	clk_scaling->need_freq_change = true;
+	clk_scaling->target_freq = *freq;
+	clk_scaling->state = *freq < clk_scaling->curr_freq ?
+		MMC_LOAD_LOW : MMC_LOAD_HIGH;
+	spin_unlock_bh(&clk_scaling->lock);
+
+	abort = __mmc_claim_host(host, NULL, &clk_scaling->devfreq_abort);
+	if (abort)
+		goto out;
+
+	/*
+	 * In case we were able to claim host there is no need to
+	 * defer the frequency change. It will be done now
+	 */
+	clk_scaling->need_freq_change = false;
+
+	err = mmc_clk_update_freq(host, *freq, clk_scaling->state);
+	if (err && err != -EAGAIN) {
+		pr_err("%s: clock scale to %lu failed with error %d\n",
+			mmc_hostname(host), *freq, err);
+	} else {
+		pr_debug("%s: clock change to %lu finished successfully (%s)\n",
+			mmc_hostname(host), *freq, current->comm);
+	}
+
+	mmc_release_host(host);
+out:
+	current->flags &= ~PF_MEMALLOC;
+	current->flags |= pflags & PF_MEMALLOC;
+	return err;
+}
+
+/**
+ * mmc_deferred_scaling() - scale clocks from data path (mmc thread context)
+ * @host: pointer to mmc host structure
+ *
+ * This function does clock scaling in case "need_freq_change" flag was set
+ * by the clock scaling logic.
+ */
+void mmc_deferred_scaling(struct mmc_host *host)
+{
+	unsigned long target_freq;
+	int err;
+
+	if (!host->clk_scaling.enable)
+		return;
+
+	spin_lock_bh(&host->clk_scaling.lock);
+
+	if (host->clk_scaling.clk_scaling_in_progress ||
+		!(host->clk_scaling.need_freq_change)) {
+		spin_unlock_bh(&host->clk_scaling.lock);
+		return;
+	}
+
+
+	atomic_inc(&host->clk_scaling.devfreq_abort);
+	target_freq = host->clk_scaling.target_freq;
+	host->clk_scaling.clk_scaling_in_progress = true;
+	host->clk_scaling.need_freq_change = false;
+	spin_unlock_bh(&host->clk_scaling.lock);
+	pr_debug("%s: doing deferred frequency change (%lu) (%s)\n",
+				mmc_hostname(host),
+				target_freq, current->comm);
+
+	err = mmc_clk_update_freq(host, target_freq,
+		host->clk_scaling.state);
+	if (err && err != -EAGAIN) {
+		pr_err("%s: failed on deferred scale clocks (%d)\n",
+			mmc_hostname(host), err);
+	} else {
+		pr_debug("%s: clocks were successfully scaled to %lu (%s)\n",
+			mmc_hostname(host),
+			target_freq, current->comm);
+	}
+	host->clk_scaling.clk_scaling_in_progress = false;
+	atomic_dec(&host->clk_scaling.devfreq_abort);
+}
+EXPORT_SYMBOL(mmc_deferred_scaling);
+
+static int mmc_devfreq_create_freq_table(struct mmc_host *host)
+{
+	int i;
+	struct mmc_devfeq_clk_scaling *clk_scaling = &host->clk_scaling;
+
+	pr_debug("%s: supported: lowest=%lu, highest=%lu\n",
+		mmc_hostname(host),
+		host->card->clk_scaling_lowest,
+		host->card->clk_scaling_highest);
+
+	/*
+	 * Create the frequency table and initialize it with default values.
+	 * Initialize it with platform specific frequencies if the frequency
+	 * table supplied by platform driver is present, otherwise initialize
+	 * it with min and max frequencies supported by the card.
+	 */
+	if (!clk_scaling->freq_table) {
+		if (clk_scaling->pltfm_freq_table_sz)
+			clk_scaling->freq_table_sz =
+				clk_scaling->pltfm_freq_table_sz;
+		else
+			clk_scaling->freq_table_sz = 2;
+
+		clk_scaling->freq_table = kzalloc(
+			(clk_scaling->freq_table_sz *
+			sizeof(*(clk_scaling->freq_table))), GFP_KERNEL);
+		if (!clk_scaling->freq_table)
+			return -ENOMEM;
+
+		if (clk_scaling->pltfm_freq_table) {
+			memcpy(clk_scaling->freq_table,
+				clk_scaling->pltfm_freq_table,
+				(clk_scaling->pltfm_freq_table_sz *
+				sizeof(*(clk_scaling->pltfm_freq_table))));
+		} else {
+			pr_debug("%s: no frequency table defined -  setting default\n",
+				mmc_hostname(host));
+			clk_scaling->freq_table[0] =
+				host->card->clk_scaling_lowest;
+			clk_scaling->freq_table[1] =
+				host->card->clk_scaling_highest;
+			goto out;
+		}
+	}
+
+	if (host->card->clk_scaling_lowest >
+		clk_scaling->freq_table[0])
+		pr_debug("%s: frequency table undershot possible freq\n",
+			mmc_hostname(host));
+
+	for (i = 0; i < clk_scaling->freq_table_sz; i++) {
+		if (clk_scaling->freq_table[i] <=
+			host->card->clk_scaling_highest)
+			continue;
+		clk_scaling->freq_table[i] =
+			host->card->clk_scaling_highest;
+		clk_scaling->freq_table_sz = i + 1;
+		pr_debug("%s: frequency table overshot possible freq (%d)\n",
+				mmc_hostname(host), clk_scaling->freq_table[i]);
+		break;
+	}
+
+out:
+	/**
+	 * devfreq requires unsigned long type freq_table while the
+	 * freq_table in clk_scaling is un32. Here allocates an individual
+	 * memory space for it and release it when exit clock scaling.
+	 */
+	clk_scaling->devfreq_profile.freq_table =  kzalloc(
+			clk_scaling->freq_table_sz *
+			sizeof(*(clk_scaling->devfreq_profile.freq_table)),
+			GFP_KERNEL);
+	if (!clk_scaling->devfreq_profile.freq_table)
+		return -ENOMEM;
+	clk_scaling->devfreq_profile.max_state = clk_scaling->freq_table_sz;
+
+	for (i = 0; i < clk_scaling->freq_table_sz; i++) {
+		clk_scaling->devfreq_profile.freq_table[i] =
+			clk_scaling->freq_table[i];
+		pr_debug("%s: freq[%d] = %u\n",
+			mmc_hostname(host), i, clk_scaling->freq_table[i]);
+	}
+
+	return 0;
+}
+
+/**
+ * mmc_init_devfreq_clk_scaling() - Initialize clock scaling
+ * @host: pointer to mmc host structure
+ *
+ * Initialize clock scaling for supported hosts. It is assumed that the caller
+ * ensure clock is running at maximum possible frequency before calling this
+ * function. Shall use struct devfreq_simple_ondemand_data to configure
+ * governor.
+ */
+int mmc_init_clk_scaling(struct mmc_host *host)
+{
+	int err;
+
+	if (!host || !host->card) {
+		pr_err("%s: unexpected host/card parameters\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	if (!mmc_can_scale_clk(host) ||
+		!host->bus_ops->change_bus_speed) {
+		pr_debug("%s: clock scaling is not supported\n",
+			mmc_hostname(host));
+		return 0;
+	}
+
+	pr_debug("registering %s dev (%p) to devfreq",
+		mmc_hostname(host),
+		mmc_classdev(host));
+
+	if (host->clk_scaling.devfreq) {
+		pr_err("%s: dev is already registered for dev %p\n",
+			mmc_hostname(host),
+			mmc_dev(host));
+		return -EPERM;
+	}
+	spin_lock_init(&host->clk_scaling.lock);
+	atomic_set(&host->clk_scaling.devfreq_abort, 0);
+	host->clk_scaling.curr_freq = host->ios.clock;
+	host->clk_scaling.clk_scaling_in_progress = false;
+	host->clk_scaling.need_freq_change = false;
+	host->clk_scaling.is_busy_started = false;
+
+	host->clk_scaling.devfreq_profile.polling_ms =
+		host->clk_scaling.polling_delay_ms;
+	host->clk_scaling.devfreq_profile.get_dev_status =
+		mmc_devfreq_get_dev_status;
+	host->clk_scaling.devfreq_profile.target = mmc_devfreq_set_target;
+	host->clk_scaling.devfreq_profile.initial_freq = host->ios.clock;
+
+	host->clk_scaling.ondemand_gov_data.simple_scaling = true;
+	host->clk_scaling.ondemand_gov_data.upthreshold =
+		host->clk_scaling.upthreshold;
+	host->clk_scaling.ondemand_gov_data.downdifferential =
+		host->clk_scaling.upthreshold - host->clk_scaling.downthreshold;
+
+	err = mmc_devfreq_create_freq_table(host);
+	if (err) {
+		pr_err("%s: fail to create devfreq frequency table\n",
+			mmc_hostname(host));
+		return err;
+	}
+
+	pr_debug("%s: adding devfreq with: upthreshold=%u downthreshold=%u polling=%u\n",
+		mmc_hostname(host),
+		host->clk_scaling.ondemand_gov_data.upthreshold,
+		host->clk_scaling.ondemand_gov_data.downdifferential,
+		host->clk_scaling.devfreq_profile.polling_ms);
+	host->clk_scaling.devfreq = devfreq_add_device(
+		mmc_classdev(host),
+		&host->clk_scaling.devfreq_profile,
+		"simple_ondemand",
+		&host->clk_scaling.ondemand_gov_data);
+	if (!host->clk_scaling.devfreq) {
+		pr_err("%s: unable to register with devfreq\n",
+			mmc_hostname(host));
+		return -EPERM;
+	}
+
+	pr_debug("%s: clk scaling is enabled for device %s (%p) with devfreq %p (clock = %uHz)\n",
+		mmc_hostname(host),
+		dev_name(mmc_classdev(host)),
+		mmc_classdev(host),
+		host->clk_scaling.devfreq,
+		host->ios.clock);
+
+	host->clk_scaling.enable = true;
+
+	return err;
+}
+EXPORT_SYMBOL(mmc_init_clk_scaling);
+
+/**
+ * mmc_exit_devfreq_clk_scaling() - Disable clock scaling
+ * @host: pointer to mmc host structure
+ *
+ * Disable clock scaling permanently.
+ */
+int mmc_exit_clk_scaling(struct mmc_host *host)
+{
+	int err;
+
+	if (!host) {
+		pr_err("%s: bad host parameter\n", __func__);
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	if (!mmc_can_scale_clk(host))
+		return 0;
+
+	if (!host->clk_scaling.devfreq) {
+		pr_err("%s: %s: no devfreq is assosiated with this device\n",
+			mmc_hostname(host), __func__);
+		return -EPERM;
+	}
+
+	err = devfreq_remove_device(host->clk_scaling.devfreq);
+	if (err) {
+		pr_err("%s: remove devfreq failed (%d)\n",
+			mmc_hostname(host), err);
+		return err;
+	}
+
+	kfree(host->clk_scaling.devfreq_profile.freq_table);
+
+	host->clk_scaling.devfreq = NULL;
+	atomic_set(&host->clk_scaling.devfreq_abort, 1);
+
+	kfree(host->clk_scaling.freq_table);
+	host->clk_scaling.freq_table = NULL;
+
+	pr_debug("%s: devfreq was removed\n", mmc_hostname(host));
+
+	return 0;
+}
+EXPORT_SYMBOL(mmc_exit_clk_scaling);
+
 static inline void mmc_complete_cmd(struct mmc_request *mrq)
 {
 	if (mrq->cap_cmd_during_tfr && !completion_done(&mrq->cmd_completion))
@@ -143,6 +690,9 @@  void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
 	struct mmc_command *cmd = mrq->cmd;
 	int err = cmd->error;
 
+	if (host->clk_scaling.is_busy_started)
+		mmc_clk_scaling_stop_busy(host, true);
+
 	/* Flag re-tuning needed on CRC errors */
 	if ((cmd->opcode != MMC_SEND_TUNING_BLOCK &&
 	    cmd->opcode != MMC_SEND_TUNING_BLOCK_HS200) &&
@@ -354,6 +904,12 @@  int mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
 		return err;
 
 	led_trigger_event(host->led, LED_FULL);
+
+	if (mmc_is_data_request(mrq)) {
+		mmc_deferred_scaling(host);
+		mmc_clk_scaling_start_busy(host, true);
+	}
+
 	__mmc_start_request(host, mrq);
 
 	return 0;
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 9d8f09a..fc0a9b7 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -34,6 +34,7 @@  struct mmc_bus_ops {
 	int (*shutdown)(struct mmc_host *);
 	int (*hw_reset)(struct mmc_host *);
 	int (*sw_reset)(struct mmc_host *);
+	int (*change_bus_speed)(struct mmc_host *, unsigned long *);
 };
 
 void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops);
@@ -46,6 +47,8 @@  struct device_node *mmc_of_find_child_device(struct mmc_host *host,
 
 void mmc_set_chip_select(struct mmc_host *host, int mode);
 void mmc_set_clock(struct mmc_host *host, unsigned int hz);
+int mmc_clk_update_freq(struct mmc_host *host,
+		unsigned long freq, enum mmc_load state);
 void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
 void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
 u32 mmc_select_voltage(struct mmc_host *host, u32 ocr);
@@ -91,6 +94,10 @@  static inline void mmc_delay(unsigned int ms)
 void mmc_add_card_debugfs(struct mmc_card *card);
 void mmc_remove_card_debugfs(struct mmc_card *card);
 
+extern bool mmc_can_scale_clk(struct mmc_host *host);
+extern int mmc_init_clk_scaling(struct mmc_host *host);
+extern int mmc_exit_clk_scaling(struct mmc_host *host);
+
 int mmc_execute_tuning(struct mmc_card *card);
 int mmc_hs200_to_hs400(struct mmc_card *card);
 int mmc_hs400_to_hs200(struct mmc_card *card);
diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index d2275c5..630ca8e 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -225,6 +225,43 @@  static int mmc_clock_opt_set(void *data, u64 val)
 DEFINE_SIMPLE_ATTRIBUTE(mmc_clock_fops, mmc_clock_opt_get, mmc_clock_opt_set,
 	"%llu\n");
 
+#include <linux/delay.h>
+
+static int mmc_scale_get(void *data, u64 *val)
+{
+	struct mmc_host *host = data;
+
+	*val = host->clk_scaling.curr_freq;
+
+	return 0;
+}
+
+static int mmc_scale_set(void *data, u64 val)
+{
+	int err = 0;
+	struct mmc_host *host = data;
+
+	mmc_claim_host(host);
+
+	/* change frequency from sysfs manually */
+	err = mmc_clk_update_freq(host, val, host->clk_scaling.state);
+	if (err == -EAGAIN)
+		err = 0;
+	else if (err)
+		pr_err("%s: clock scale to %llu failed with error %d\n",
+			mmc_hostname(host), val, err);
+	else
+		pr_debug("%s: clock change to %llu finished successfully (%s)\n",
+			mmc_hostname(host), val, current->comm);
+
+	mmc_release_host(host);
+
+	return err;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(mmc_scale_fops, mmc_scale_get, mmc_scale_set,
+	"%llu\n");
+
 void mmc_add_host_debugfs(struct mmc_host *host)
 {
 	struct dentry *root;
@@ -253,6 +290,15 @@  void mmc_add_host_debugfs(struct mmc_host *host)
 			&mmc_clock_fops))
 		goto err_node;
 
+	if (!debugfs_create_file("scale", 0600, root, host,
+		&mmc_scale_fops))
+		goto err_node;
+
+	if (!debugfs_create_bool("skip_clk_scale_freq_update",
+		0600, root,
+		&host->clk_scaling.skip_clk_scale_freq_update))
+		goto err_node;
+
 #ifdef CONFIG_FAIL_MMC_REQUEST
 	if (fail_request)
 		setup_fault_attr(&fail_default_attr, fail_request);
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index abf9e88..1e46aa4 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -32,6 +32,10 @@ 
 #include "pwrseq.h"
 #include "sdio_ops.h"
 
+#define MMC_DEVFRQ_DEFAULT_UP_THRESHOLD 35
+#define MMC_DEVFRQ_DEFAULT_DOWN_THRESHOLD 5
+#define MMC_DEVFRQ_DEFAULT_POLLING_MSEC 100
+
 #define cls_dev_to_mmc_host(d)	container_of(d, struct mmc_host, class_dev)
 
 static DEFINE_IDA(mmc_host_ida);
@@ -435,6 +439,10 @@  int mmc_add_host(struct mmc_host *host)
 		return err;
 
 	led_trigger_register_simple(dev_name(&host->class_dev), &host->led);
+	host->clk_scaling.upthreshold = MMC_DEVFRQ_DEFAULT_UP_THRESHOLD;
+	host->clk_scaling.downthreshold = MMC_DEVFRQ_DEFAULT_DOWN_THRESHOLD;
+	host->clk_scaling.polling_delay_ms = MMC_DEVFRQ_DEFAULT_POLLING_MSEC;
+	host->clk_scaling.skip_clk_scale_freq_update = false;
 
 #ifdef CONFIG_DEBUG_FS
 	mmc_add_host_debugfs(host);
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 4466f5d..c8aedf3 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1526,6 +1526,170 @@  static int mmc_hs200_tuning(struct mmc_card *card)
 }
 
 /*
+ * Scale down from HS400 to HS in order to allow frequency change.
+ * This is needed for cards that doesn't support changing frequency in HS400
+ */
+static int mmc_scale_low(struct mmc_host *host, unsigned long freq)
+{
+	int err = 0;
+
+	mmc_set_timing(host, MMC_TIMING_LEGACY);
+	mmc_set_clock(host, MMC_HIGH_26_MAX_DTR);
+
+	err = mmc_select_hs(host->card);
+	if (err) {
+		pr_err("%s: %s: scaling low: failed (%d)\n",
+		       mmc_hostname(host), __func__, err);
+		return err;
+	}
+
+	err = mmc_select_bus_width(host->card);
+	if (err < 0) {
+		pr_err("%s: %s: select_bus_width failed(%d)\n",
+			mmc_hostname(host), __func__, err);
+		return err;
+	}
+
+	mmc_set_clock(host, freq);
+
+	return 0;
+}
+
+/*
+ * Scale UP from HS to HS200/H400
+ */
+static int mmc_scale_high(struct mmc_host *host)
+{
+	int err = 0;
+
+	if (mmc_card_ddr52(host->card)) {
+		mmc_set_timing(host, MMC_TIMING_LEGACY);
+		mmc_set_clock(host, MMC_HIGH_26_MAX_DTR);
+	}
+
+	if (!host->card->ext_csd.strobe_support) {
+		if (!(host->card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200)) {
+			pr_err("%s: %s: card does not support HS200\n",
+				mmc_hostname(host), __func__);
+			WARN_ON(1);
+			return -EPERM;
+		}
+
+		err = mmc_select_hs200(host->card);
+		if (err) {
+			pr_err("%s: %s: selecting HS200 failed (%d)\n",
+				mmc_hostname(host), __func__, err);
+			return err;
+		}
+
+		mmc_set_bus_speed(host->card);
+
+		err = mmc_hs200_tuning(host->card);
+		if (err) {
+			pr_err("%s: %s: hs200 tuning failed (%d)\n",
+				mmc_hostname(host), __func__, err);
+			return err;
+		}
+
+		if (!(host->card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400)) {
+			pr_debug("%s: card does not support HS400\n",
+				mmc_hostname(host));
+			return 0;
+		}
+	}
+
+	err = mmc_select_hs400(host->card);
+	if (err) {
+		pr_err("%s: %s: select hs400 failed (%d)\n",
+			mmc_hostname(host), __func__, err);
+		return err;
+	}
+
+	return err;
+}
+
+static int mmc_set_clock_bus_speed(struct mmc_card *card, unsigned long freq)
+{
+	int err = 0;
+
+	if (freq == MMC_HS200_MAX_DTR)
+		err = mmc_scale_high(card->host);
+	else
+		err = mmc_scale_low(card->host, freq);
+
+	return err;
+}
+
+static inline unsigned long mmc_ddr_freq_accommodation(unsigned long freq)
+{
+	if (freq == MMC_HIGH_DDR_MAX_DTR)
+		return freq;
+
+	return freq/2;
+}
+
+/**
+ * mmc_change_bus_speed() - Change MMC card bus frequency at runtime
+ * @host: pointer to mmc host structure
+ * @freq: pointer to desired frequency to be set
+ *
+ * Change the MMC card bus frequency at runtime after the card is
+ * initialized. Callers are expected to make sure of the card's
+ * state (DATA/RCV/TRANSFER) before changing the frequency at runtime.
+ *
+ * If the frequency to change is greater than max. supported by card,
+ * *freq is changed to max. supported by card. If it is less than min.
+ * supported by host, *freq is changed to min. supported by host.
+ * Host is assumed to be calimed while calling this funciton.
+ */
+static int mmc_change_bus_speed(struct mmc_host *host, unsigned long *freq)
+{
+	int err = 0;
+	struct mmc_card *card;
+	unsigned long actual_freq;
+
+	card = host->card;
+
+	if (!card || !freq) {
+		err = -EINVAL;
+		goto out;
+	}
+	actual_freq = *freq;
+
+	WARN_ON(!host->claimed);
+
+	/*
+	 * For scaling up/down HS400 we'll need special handling,
+	 * for other timings we can simply do clock frequency change
+	 */
+	if (mmc_card_hs400(card) ||
+		(!mmc_card_hs200(host->card) && *freq == MMC_HS200_MAX_DTR)) {
+		err = mmc_set_clock_bus_speed(card, *freq);
+		if (err) {
+			pr_err("%s: %s: failed (%d)to set bus and clock speed (freq=%lu)\n",
+				mmc_hostname(host), __func__, err, *freq);
+			goto out;
+		}
+	} else if (mmc_card_hs200(host->card)) {
+		mmc_set_clock(host, *freq);
+		err = mmc_hs200_tuning(host->card);
+		if (err) {
+			pr_warn("%s: %s: tuning execution failed %d\n",
+				mmc_hostname(card->host),
+				__func__, err);
+			mmc_set_clock(host, host->clk_scaling.curr_freq);
+		}
+	} else {
+		if (mmc_card_ddr52(host->card))
+			actual_freq = mmc_ddr_freq_accommodation(*freq);
+		mmc_set_clock(host, actual_freq);
+	}
+
+out:
+	return err;
+}
+
+/*
  * Handle the detection and initialisation of a card.
  *
  * In the case of a resume, "oldcard" will contain the card
@@ -1751,6 +1915,16 @@  static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	card->clk_scaling_lowest = host->f_min;
+	if ((card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400) ||
+			(card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200))
+		card->clk_scaling_highest = card->ext_csd.hs200_max_dtr;
+	else if ((card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS) ||
+			(card->mmc_avail_type & EXT_CSD_CARD_TYPE_DDR_52))
+		card->clk_scaling_highest = card->ext_csd.hs_max_dtr;
+	else
+		card->clk_scaling_highest = card->csd.max_dtr;
+
 	/*
 	 * Choose the power class with selected bus interface
 	 */
@@ -1942,6 +2116,7 @@  static int mmc_poweroff_notify(struct mmc_card *card, unsigned int notify_type)
  */
 static void mmc_remove(struct mmc_host *host)
 {
+	mmc_exit_clk_scaling(host);
 	mmc_remove_card(host->card);
 	host->card = NULL;
 }
@@ -2064,6 +2239,13 @@  static int mmc_shutdown(struct mmc_host *host)
 	int err = 0;
 
 	/*
+	 * Exit clock scaling so that it doesn't kick in after
+	 * power off notification is sent
+	 */
+	if (host->caps2 & MMC_CAP2_CLK_SCALE)
+		mmc_exit_clk_scaling(host);
+
+	/*
 	 * In a specific case for poweroff notify, we need to resume the card
 	 * before we can shutdown it properly.
 	 */
@@ -2132,6 +2314,7 @@  static int mmc_can_reset(struct mmc_card *card)
 static int _mmc_hw_reset(struct mmc_host *host)
 {
 	struct mmc_card *card = host->card;
+	int ret;
 
 	/*
 	 * In the case of recovery, we can't expect flushing the cache to work
@@ -2151,7 +2334,15 @@  static int _mmc_hw_reset(struct mmc_host *host)
 		mmc_power_cycle(host, card->ocr);
 		mmc_pwrseq_reset(host);
 	}
-	return mmc_init_card(host, card->ocr, card);
+
+	ret = mmc_init_card(host, card->ocr, card);
+	if (ret) {
+		pr_err("%s: %s: mmc_init_card failed (%d)\n",
+			mmc_hostname(host), __func__, ret);
+		return ret;
+	}
+
+	return ret;
 }
 
 static const struct mmc_bus_ops mmc_ops = {
@@ -2164,6 +2355,7 @@  static int _mmc_hw_reset(struct mmc_host *host)
 	.alive = mmc_alive,
 	.shutdown = mmc_shutdown,
 	.hw_reset = _mmc_hw_reset,
+	.change_bus_speed = mmc_change_bus_speed,
 };
 
 /*
@@ -2220,6 +2412,12 @@  int mmc_attach_mmc(struct mmc_host *host)
 		goto remove_card;
 
 	mmc_claim_host(host);
+	err = mmc_init_clk_scaling(host);
+	if (err) {
+		mmc_release_host(host);
+		goto remove_card;
+	}
+
 	return 0;
 
 remove_card:
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index d0d9f90..40144c1 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -892,7 +892,10 @@  unsigned mmc_sd_get_max_clock(struct mmc_card *card)
 {
 	unsigned max_dtr = (unsigned int)-1;
 
-	if (mmc_card_hs(card)) {
+	if (mmc_card_uhs(card)) {
+		if (max_dtr > card->sw_caps.uhs_max_dtr)
+			max_dtr = card->sw_caps.uhs_max_dtr;
+	} else if (mmc_card_hs(card)) {
 		if (max_dtr > card->sw_caps.hs_max_dtr)
 			max_dtr = card->sw_caps.hs_max_dtr;
 	} else if (max_dtr > card->csd.max_dtr) {
@@ -1059,6 +1062,9 @@  static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	card->clk_scaling_highest = mmc_sd_get_max_clock(card);
+	card->clk_scaling_lowest = host->f_min;
+
 	if (host->caps2 & MMC_CAP2_AVOID_3_3V &&
 	    host->ios.signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
 		pr_err("%s: Host failed to negotiate down from 3.3V\n",
@@ -1082,6 +1088,7 @@  static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
  */
 static void mmc_sd_remove(struct mmc_host *host)
 {
+	mmc_exit_clk_scaling(host);
 	mmc_remove_card(host->card);
 	host->card = NULL;
 }
@@ -1228,6 +1235,62 @@  static int mmc_sd_hw_reset(struct mmc_host *host)
 	return mmc_sd_init_card(host, host->card->ocr, host->card);
 }
 
+/**
+ * mmc_sd_change_bus_speed() - Change SD card bus frequency at runtime
+ * @host: pointer to mmc host structure
+ * @freq: pointer to desired frequency to be set
+ *
+ * Change the SD card bus frequency at runtime after the card is
+ * initialized. Callers are expected to make sure of the card's
+ * state (DATA/RCV/TRANSFER) beforing changing the frequency at runtime.
+ *
+ * If the frequency to change is greater than max. supported by card,
+ * *freq is changed to max. supported by card and if it is less than min.
+ * supported by host, *freq is changed to min. supported by host.
+ */
+static int mmc_sd_change_bus_speed(struct mmc_host *host, unsigned long *freq)
+{
+	int err = 0;
+	struct mmc_card *card;
+
+	mmc_claim_host(host);
+	/*
+	 * Assign card pointer after claiming host to avoid race
+	 * conditions that may arise during removal of the card.
+	 */
+	card = host->card;
+
+	/* sanity checks */
+	if (!card || !freq) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	mmc_set_clock(host, (unsigned int) (*freq));
+
+	if (!mmc_host_is_spi(card->host) && mmc_card_uhs(card)
+			&& card->host->ops->execute_tuning) {
+		/*
+		 * We try to probe host driver for tuning for any
+		 * frequency, it is host driver responsibility to
+		 * perform actual tuning only when required.
+		 */
+		err = card->host->ops->execute_tuning(card->host,
+				MMC_SEND_TUNING_BLOCK);
+
+		if (err) {
+			pr_warn("%s: %s: tuning execution failed %d. Restoring to previous clock %lu\n",
+				   mmc_hostname(card->host), __func__, err,
+				   host->clk_scaling.curr_freq);
+			mmc_set_clock(host, host->clk_scaling.curr_freq);
+		}
+	}
+
+out:
+	mmc_release_host(host);
+	return err;
+}
+
 static const struct mmc_bus_ops mmc_sd_ops = {
 	.remove = mmc_sd_remove,
 	.detect = mmc_sd_detect,
@@ -1238,6 +1301,7 @@  static int mmc_sd_hw_reset(struct mmc_host *host)
 	.alive = mmc_sd_alive,
 	.shutdown = mmc_sd_suspend,
 	.hw_reset = mmc_sd_hw_reset,
+	.change_bus_speed = mmc_sd_change_bus_speed,
 };
 
 /*
@@ -1292,6 +1356,12 @@  int mmc_attach_sd(struct mmc_host *host)
 		goto remove_card;
 
 	mmc_claim_host(host);
+	err = mmc_init_clk_scaling(host);
+	if (err) {
+		mmc_release_host(host);
+		goto remove_card;
+	}
+
 	return 0;
 
 remove_card:
diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index b5519a5..e9fe8c6 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -1705,6 +1705,43 @@  static int sdhci_msm_register_vreg(struct sdhci_msm_host *msm_host)
 
 MODULE_DEVICE_TABLE(of, sdhci_msm_dt_match);
 
+int sdhci_msm_dt_get_array(struct device *dev, const char *prop_name,
+				 u32 **out, int *len, u32 size)
+{
+	int ret = 0;
+	struct device_node *np = dev->of_node;
+	size_t sz;
+	u32 *arr = NULL;
+
+	if (!of_get_property(np, prop_name, len)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	sz = *len = *len / sizeof(*arr);
+	if (sz <= 0 || (size > 0 && (sz > size))) {
+		dev_err(dev, "%s invalid size\n", prop_name);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	arr = devm_kzalloc(dev, sz * sizeof(*arr), GFP_KERNEL);
+	if (!arr) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = of_property_read_u32_array(np, prop_name, arr, sz);
+	if (ret < 0) {
+		dev_err(dev, "%s failed reading array %d\n", prop_name, ret);
+		goto out;
+	}
+	*out = arr;
+out:
+	if (ret)
+		*len = 0;
+	return ret;
+}
+
 static const struct sdhci_ops sdhci_msm_ops = {
 	.reset = sdhci_reset,
 	.set_clock = sdhci_msm_set_clock,
diff --git a/drivers/mmc/host/sdhci-pltfm.c b/drivers/mmc/host/sdhci-pltfm.c
index 02bea61..354fc68 100644
--- a/drivers/mmc/host/sdhci-pltfm.c
+++ b/drivers/mmc/host/sdhci-pltfm.c
@@ -36,6 +36,9 @@ 
 #endif
 #include "sdhci-pltfm.h"
 
+int sdhci_msm_dt_get_array(struct device *dev, const char *prop_name,
+				 u32 **out, int *len, u32 size);
+
 unsigned int sdhci_pltfm_clk_get_max_clock(struct sdhci_host *host)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -101,6 +104,14 @@  void sdhci_get_of_property(struct platform_device *pdev)
 
 	of_property_read_u32(np, "clock-frequency", &pltfm_host->clock);
 
+	if (sdhci_msm_dt_get_array(&pdev->dev, "qcom,devfreq,freq-table",
+			&host->mmc->clk_scaling.pltfm_freq_table,
+			&host->mmc->clk_scaling.pltfm_freq_table_sz, 0))
+		pr_debug("no clock scaling frequencies were supplied\n");
+	else if (!host->mmc->clk_scaling.pltfm_freq_table ||
+			!host->mmc->clk_scaling.pltfm_freq_table_sz)
+		pr_err("bad dts clock scaling frequencies\n");
+
 	if (of_find_property(np, "keep-power-in-suspend", NULL))
 		host->mmc->pm_caps |= MMC_PM_KEEP_POWER;
 
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 162b9af..f0aafab 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2427,6 +2427,32 @@  static void sdhci_card_event(struct mmc_host *mmc)
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
+static inline void sdhci_update_power_policy(struct sdhci_host *host,
+		enum sdhci_power_policy policy)
+{
+	host->power_policy = policy;
+}
+
+static int sdhci_notify_load(struct mmc_host *mmc, enum mmc_load state)
+{
+	int err = 0;
+	struct sdhci_host *host = mmc_priv(mmc);
+
+	switch (state) {
+	case MMC_LOAD_HIGH:
+		sdhci_update_power_policy(host, SDHCI_PERFORMANCE_MODE);
+		break;
+	case MMC_LOAD_LOW:
+		sdhci_update_power_policy(host, SDHCI_POWER_SAVE_MODE);
+		break;
+	default:
+		err = -EINVAL;
+		break;
+	}
+
+	return err;
+}
+
 static const struct mmc_host_ops sdhci_ops = {
 	.request	= sdhci_request,
 	.post_req	= sdhci_post_req,
@@ -2441,6 +2467,7 @@  static void sdhci_card_event(struct mmc_host *mmc)
 	.execute_tuning			= sdhci_execute_tuning,
 	.card_event			= sdhci_card_event,
 	.card_busy	= sdhci_card_busy,
+	.notify_load = sdhci_notify_load,
 };
 
 /*****************************************************************************\
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 3b0c97a..740471f 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -346,6 +346,12 @@  enum sdhci_cookie {
 	COOKIE_MAPPED,		/* mapped by sdhci_prepare_data() */
 };
 
+enum sdhci_power_policy {
+	SDHCI_PERFORMANCE_MODE,
+	SDHCI_POWER_SAVE_MODE,
+	SDHCI_POWER_POLICY_NUM /* Always keep this one last */
+};
+
 struct sdhci_host {
 	/* Data set by hardware interface driver */
 	const char *hw_name;	/* Hardware bus name */
@@ -562,6 +568,8 @@  struct sdhci_host {
 	/* Delay (ms) between tuning commands */
 	int			tuning_delay;
 
+	enum sdhci_power_policy power_policy;
+
 	/* Host SDMA buffer boundary. */
 	u32			sdma_boundary;
 
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index de73778..c713581 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -245,6 +245,10 @@  struct mmc_card {
 	struct mmc_host		*host;		/* the host this device belongs to */
 	struct device		dev;		/* the device */
 	u32			ocr;		/* the current OCR setting */
+	unsigned long		clk_scaling_lowest;	/* lowest scaleable*/
+							/* frequency */
+	unsigned long		clk_scaling_highest;	/* highest scaleable */
+
 	unsigned int		rca;		/* relative card address of device */
 	unsigned int		type;		/* card type */
 #define MMC_TYPE_MMC		0		/* MMC card */
@@ -308,6 +312,7 @@  struct mmc_card {
 	unsigned int    nr_parts;
 
 	unsigned int		bouncesz;	/* Bounce buffer size */
+	unsigned int		part_curr;
 };
 
 static inline bool mmc_large_sector(struct mmc_card *card)
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 64300a4..321ab39 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -12,6 +12,7 @@ 
 
 #include <linux/sched.h>
 #include <linux/device.h>
+#include <linux/devfreq.h>
 #include <linux/fault-inject.h>
 
 #include <linux/mmc/core.h>
@@ -82,6 +83,12 @@  struct mmc_ios {
 
 struct mmc_host;
 
+/* states to represent load on the host */
+enum mmc_load {
+	MMC_LOAD_HIGH,
+	MMC_LOAD_LOW,
+};
+
 struct mmc_host_ops {
 	/*
 	 * It is optional for the host to implement pre_req and post_req in
@@ -161,6 +168,7 @@  struct mmc_host_ops {
 	 */
 	int	(*multi_io_quirk)(struct mmc_card *card,
 				  unsigned int direction, int blk_size);
+	int	(*notify_load)(struct mmc_host *, enum mmc_load);
 };
 
 struct mmc_cqe_ops {
@@ -260,9 +268,60 @@  struct mmc_ctx {
 	struct task_struct *task;
 };
 
+/**
+ * struct mmc_devfeq_clk_scaling - main context for MMC clock scaling logic
+ *
+ * @lock: spinlock to protect statistics
+ * @devfreq: struct that represent mmc-host as a client for devfreq
+ * @devfreq_profile: MMC device profile, mostly polling interval and callbacks
+ * @ondemand_gov_data: struct supplied to ondemmand governor (thresholds)
+ * @state: load state, can be HIGH or LOW. used to notify mmc_host_ops callback
+ * @start_busy: timestamped armed once a data request is started
+ * @measure_interval_start: timestamped armed once a measure interval started
+ * @devfreq_abort: flag to sync between different contexts relevant to devfreq
+ * @skip_clk_scale_freq_update: flag that enable/disable frequency change
+ * @freq_table_sz: table size of frequencies supplied to devfreq
+ * @freq_table: frequencies table supplied to devfreq
+ * @curr_freq: current frequency
+ * @polling_delay_ms: polling interval for status collection used by devfreq
+ * @upthreshold: up-threshold supplied to ondemand governor
+ * @downthreshold: down-threshold supplied to ondemand governor
+ * @need_freq_change: flag indicating if a frequency change is required
+ * @clk_scaling_in_progress: flag indicating if there's ongoing frequency change
+ * @is_busy_started: flag indicating if a request is handled by the HW
+ * @enable: flag indicating if the clock scaling logic is enabled for this host
+ */
+struct mmc_devfeq_clk_scaling {
+	spinlock_t	lock;
+	struct		devfreq *devfreq;
+	struct		devfreq_dev_profile devfreq_profile;
+	struct		devfreq_simple_ondemand_data ondemand_gov_data;
+	enum mmc_load	state;
+	ktime_t		start_busy;
+	ktime_t		measure_interval_start;
+	atomic_t	devfreq_abort;
+	bool		skip_clk_scale_freq_update;
+	int		freq_table_sz;
+	int		pltfm_freq_table_sz;
+	u32		*freq_table;
+	u32		*pltfm_freq_table;
+	unsigned long	total_busy_time_us;
+	unsigned long	target_freq;
+	unsigned long	curr_freq;
+	unsigned long	polling_delay_ms;
+	unsigned int	upthreshold;
+	unsigned int	downthreshold;
+	bool		need_freq_change;
+	bool		clk_scaling_in_progress;
+	bool		is_busy_started;
+	bool		enable;
+};
+
+
 struct mmc_host {
 	struct device		*parent;
 	struct device		class_dev;
+	struct mmc_devfeq_clk_scaling	clk_scaling;
 	int			index;
 	const struct mmc_host_ops *ops;
 	struct mmc_pwrseq	*pwrseq;
@@ -360,6 +419,7 @@  struct mmc_host {
 #define MMC_CAP2_CQE		(1 << 23)	/* Has eMMC command queue engine */
 #define MMC_CAP2_CQE_DCMD	(1 << 24)	/* CQE can issue a direct command */
 #define MMC_CAP2_AVOID_3_3V	(1 << 25)	/* Host must negotiate down from 3.3V */
+#define MMC_CAP2_CLK_SCALE      (1 << 26)       /* Allow dynamic clk scaling */
 
 	int			fixed_drv_type;	/* fixed driver type for non-removable media */
 
@@ -523,6 +583,16 @@  static inline int mmc_regulator_set_vqmmc(struct mmc_host *mmc,
 u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max);
 int mmc_regulator_get_supply(struct mmc_host *mmc);
 
+static inline void mmc_host_clear_sdr104(struct mmc_host *host)
+{
+	host->caps &= ~MMC_CAP_UHS_SDR104;
+}
+
+static inline void mmc_host_set_sdr104(struct mmc_host *host)
+{
+	host->caps |= MMC_CAP_UHS_SDR104;
+}
+
 static inline int mmc_card_is_removable(struct mmc_host *host)
 {
 	return !(host->caps & MMC_CAP_NONREMOVABLE);