diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index bb22ffd..1018ccc1 100644
--- a/drivers/mmc/core/Kconfig
+++ b/drivers/mmc/core/Kconfig
@@ -16,3 +16,14 @@ config MMC_UNSAFE_RESUME
 
 	  This option sets a default which can be overridden by the
 	  module parameter "removable=0" or "removable=1".
+
+config MMC_CLKGATE
+	bool "MMC host clock gating (EXPERIMENTAL)"
+	depends on EXPERIMENTAL
+	help
+	  This will attempt to agressively gate the clock to the MMC card.
+	  This is done to save power due to gating off the logic and bus
+	  noise when the MMC card is not in use. Your host driver has to
+	  support handling this in order for it to be of any use.
+
+	  If unsure, say N.
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 8f86d70..e74e767 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -130,6 +130,8 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
 
 		if (mrq->done)
 			mrq->done(mrq);
+
+		mmc_host_clk_gate(host);
 	}
 }
 
@@ -190,6 +192,7 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
 			mrq->stop->mrq = mrq;
 		}
 	}
+	mmc_host_clk_ungate(host);
 	host->ops->request(host, mrq);
 }
 
@@ -296,7 +299,7 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
 
 		timeout_us = data->timeout_ns / 1000;
 		timeout_us += data->timeout_clks * 1000 /
-			(card->host->ios.clock / 1000);
+			(mmc_host_clk_rate(card->host) / 1000);
 
 		if (data->flags & MMC_DATA_WRITE)
 			/*
@@ -641,6 +644,40 @@ void mmc_set_clock(struct mmc_host *host, unsigned int hz)
 	mmc_set_ios(host);
 }
 
+#ifdef CONFIG_MMC_CLKGATE
+/*
+ * This gates the clock by setting it to 0 Hz.
+ */
+void mmc_gate_clock(struct mmc_host *host)
+{
+	host->clk_old = host->ios.clock;
+	host->ios.clock = 0;
+	host->clk_gated = true;
+	mmc_set_ios(host);
+}
+
+/*
+ * This restores the clock from gating by using the cached
+ * clock value.
+ */
+void mmc_ungate_clock(struct mmc_host *host)
+{
+	/*
+	 * We should previously have gated the clock, so the clock
+	 * shall be 0 here!
+	 * The clock may however be 0 during intialization,
+	 * when some request operations are performed before setting
+	 * the frequency. When ungate is requested in that situation
+	 * we just ignore the call.
+	 */
+	if (host->clk_old) {
+		BUG_ON(host->ios.clock);
+		mmc_set_clock(host, host->clk_old);
+	}
+	host->clk_gated = false;
+}
+#endif
+
 /*
  * Change the bus mode (open drain/push-pull) of a host.
  */
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 77240cd..9972808 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -33,6 +33,8 @@ void mmc_init_erase(struct mmc_card *card);
 
 void mmc_set_chip_select(struct mmc_host *host, int mode);
 void mmc_set_clock(struct mmc_host *host, unsigned int hz);
+void mmc_gate_clock(struct mmc_host *host);
+void mmc_ungate_clock(struct mmc_host *host);
 void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
 void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
 void mmc_set_bus_width_ddr(struct mmc_host *host, unsigned int width,
diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index eed1405..998797e 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -183,6 +183,11 @@ void mmc_add_host_debugfs(struct mmc_host *host)
 			&mmc_clock_fops))
 		goto err_node;
 
+#ifdef CONFIG_MMC_CLKGATE
+	if (!debugfs_create_u32("clk_delay", (S_IRUSR | S_IWUSR),
+				root, &host->clk_delay))
+		goto err_node;
+#endif
 	return;
 
 err_node:
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 10b8af2..dc39605 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2003 Russell King, All Rights Reserved.
  *  Copyright (C) 2007-2008 Pierre Ossman
+ *  Copyright (C) 2010 Linus Walleij
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -50,6 +51,187 @@ void mmc_unregister_host_class(void)
 static DEFINE_IDR(mmc_host_idr);
 static DEFINE_SPINLOCK(mmc_host_lock);
 
+#ifdef CONFIG_MMC_CLKGATE
+
+/*
+ * Enabling clock gating will make the core call out to the host
+ * once up and once down when it performs a request or card operation
+ * intermingled in any fashion. The driver will see this through
+ * set_ios() operations with ios.clock field set to 0 to gate
+ * (disable) the block clock, and to the old frequency to enable
+ * it again.
+ */
+static void mmc_host_clk_gate_delayed(struct mmc_host *host)
+{
+	unsigned long tick_ns;
+	unsigned long freq = host->ios.clock;
+	unsigned long flags;
+	int users;
+
+	if (!freq) {
+		pr_err("%s: frequency set to 0 in disable function, "
+		       "this means the clock is already disabled.\n",
+		       mmc_hostname(host));
+		return;
+	}
+	/*
+	 * New requests may have appeared while we were scheduling,
+	 * then there is no reason to delay the check before
+	 * clk_disable().
+	 */
+	spin_lock_irqsave(&host->clk_lock, flags);
+	users = host->clk_requests;
+	/*
+	 * Delay 8 bus cycles (from MMC spec) before attempting
+	 * to disable the MMCI block clock. The reference count
+	 * may have gone up again after this delay due to
+	 * rescheduling!
+	 */
+	if (!users) {
+		spin_unlock_irqrestore(&host->clk_lock, flags);
+		tick_ns = DIV_ROUND_UP(1000000000, freq);
+		ndelay(host->clk_delay * tick_ns);
+	} else {
+		/* New users appeared while waiting for this work */
+		host->clk_pending_gate = false;
+		spin_unlock_irqrestore(&host->clk_lock, flags);
+		return;
+	}
+	spin_lock_irqsave(&host->clk_lock, flags);
+	if (!host->clk_requests) {
+		spin_unlock_irqrestore(&host->clk_lock, flags);
+		/* this will set host->ios.clock to 0 */
+		mmc_gate_clock(host);
+		spin_lock_irqsave(&host->clk_lock, flags);
+		pr_debug("%s: disabled MCI clock\n",
+			 mmc_hostname(host));
+	}
+	host->clk_pending_gate = false;
+	spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
+/*
+ * Internal work. Work to disable the clock at some later point.
+ */
+static void mmc_host_clk_gate_work(struct work_struct *work)
+{
+	struct mmc_host *host = container_of(work, struct mmc_host,
+					      clk_disable_work);
+
+	mmc_host_clk_gate_delayed(host);
+}
+
+/*
+ *	mmc_host_clk_ungate - make sure the host ios.clock is
+ *	restored to some non-zero value past this call.
+ *	@host: host to ungate.
+ *
+ *	Increase clock reference count and ungate clock if first user.
+ */
+void mmc_host_clk_ungate(struct mmc_host *host)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&host->clk_lock, flags);
+	if (host->clk_gated) {
+		spin_unlock_irqrestore(&host->clk_lock, flags);
+		mmc_ungate_clock(host);
+		spin_lock_irqsave(&host->clk_lock, flags);
+		pr_debug("%s: ungated MCI clock\n",
+			 mmc_hostname(host));
+	}
+	host->clk_requests++;
+	spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
+/*
+ *	mmc_host_clk_gate - call the host driver with ios.clock
+ *	set to zero as often as possible so as to make it
+ *	possible to gate off hardware MCI clocks.
+ *	@host: host to gate.
+ *
+ *	Decrease clock reference count and schedule disablement of clock.
+ */
+void mmc_host_clk_gate(struct mmc_host *host)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&host->clk_lock, flags);
+	host->clk_requests--;
+	if (!host->clk_requests) {
+		host->clk_pending_gate = true;
+		schedule_work(&host->clk_disable_work);
+	}
+	spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
+/*
+ *	mmc_host_clk_rate - get current clock frequency setting no matter
+ *	whether it's gated or not.
+ *	@host: host to get the clock frequency for.
+ */
+unsigned int mmc_host_clk_rate(struct mmc_host *host)
+{
+	unsigned long freq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&host->clk_lock, flags);
+	if (host->clk_gated)
+		freq = host->clk_old;
+	else
+		freq = host->ios.clock;
+	spin_unlock_irqrestore(&host->clk_lock, flags);
+	return freq;
+}
+
+/*
+ *	mmc_host_clk_init - set up clock gating code
+ *	@host: host with potential hardware clock to control
+ */
+static inline void mmc_host_clk_init(struct mmc_host *host)
+{
+	host->clk_requests = 0;
+	host->clk_delay = 8; /* hold MCI clock in 8 cycles by default */
+	host->clk_gated = false;
+	host->clk_pending_gate = false;
+	INIT_WORK(&host->clk_disable_work, mmc_host_clk_gate_work);
+	spin_lock_init(&host->clk_lock);
+}
+
+/*
+ *	mmc_host_clk_exit - shut down clock gating code
+ *	@host: host with potential hardware clock to control
+ */
+static inline void mmc_host_clk_exit(struct mmc_host *host)
+{
+	if (cancel_work_sync(&host->clk_disable_work))
+		mmc_host_clk_gate_delayed(host);
+	BUG_ON(host->clk_requests > 0);
+}
+
+#else
+inline void mmc_host_clk_ungate(struct mmc_host *host)
+{
+}
+
+inline void mmc_host_clk_gate(struct mmc_host *host)
+{
+}
+
+inline unsigned int mmc_host_clk_rate(struct mmc_host *host)
+{
+	return host->ios.clock;
+}
+
+static inline void mmc_host_clk_init(struct mmc_host *host)
+{
+}
+
+static inline void mmc_host_clk_exit(struct mmc_host *host)
+{
+}
+#endif
+
 /**
  *	mmc_alloc_host - initialise the per-host structure.
  *	@extra: sizeof private data structure
@@ -82,6 +264,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 	host->class_dev.class = &mmc_host_class;
 	device_initialize(&host->class_dev);
 
+	mmc_host_clk_init(host);
+
 	spin_lock_init(&host->lock);
 	init_waitqueue_head(&host->wq);
 	INIT_DELAYED_WORK(&host->detect, mmc_rescan);
@@ -163,6 +347,8 @@ void mmc_remove_host(struct mmc_host *host)
 	device_del(&host->class_dev);
 
 	led_trigger_unregister_simple(host->led);
+
+	mmc_host_clk_exit(host);
 }
 
 EXPORT_SYMBOL(mmc_remove_host);
@@ -183,4 +369,3 @@ void mmc_free_host(struct mmc_host *host)
 }
 
 EXPORT_SYMBOL(mmc_free_host);
-
diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
index 8c87e11..0529b1f 100644
--- a/drivers/mmc/core/host.h
+++ b/drivers/mmc/core/host.h
@@ -10,9 +10,13 @@
  */
 #ifndef _MMC_CORE_HOST_H
 #define _MMC_CORE_HOST_H
+#include <linux/mmc/host.h>
 
 int mmc_register_host_class(void);
 void mmc_unregister_host_class(void);
+void mmc_host_clk_ungate(struct mmc_host *host);
+void mmc_host_clk_gate(struct mmc_host *host);
+unsigned int mmc_host_clk_rate(struct mmc_host *host);
 
 void mmc_host_deeper_disable(struct work_struct *work);
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 6d87f68..c38c400 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -171,6 +171,16 @@ struct mmc_host {
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */
 
+#ifdef CONFIG_MMC_CLKGATE
+	int			clk_requests;	/* internal reference counter */
+	unsigned int		clk_delay;	/* number of MCI clk hold cycles */
+	bool			clk_gated;	/* clock gated */
+	bool			clk_pending_gate; /* pending clock gating */
+	struct work_struct	clk_disable_work; /* delayed clock disablement */
+	unsigned int		clk_old;	/* old clock value cache */
+	spinlock_t		clk_lock;	/* lock for clk fields */
+#endif
+
 	/* host specific block data */
 	unsigned int		max_seg_size;	/* see blk_queue_max_segment_size */
 	unsigned short		max_segs;	/* see blk_queue_max_segments */
