7 files changed, 315 insertions, 2 deletions

diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index bb22ffd76ef8..ef103871517f 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 aggressively 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 a3a780faf85a..722af2dce3bb 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)
                         /*
@@ -614,6 +617,8 @@ static inline void mmc_set_ios(struct mmc_host *host)
                  ios->power_mode, ios->chip_select, ios->vdd,
                  ios->bus_width, ios->timing);
 
+        if (ios->clock > 0)
+                mmc_set_ungated(host);
         host->ops->set_ios(host, ios);
 }
 
@@ -641,6 +646,61 @@ 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)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&host->clk_lock, flags);
+        host->clk_old = host->ios.clock;
+        host->ios.clock = 0;
+        host->clk_gated = true;
+        spin_unlock_irqrestore(&host->clk_lock, flags);
+        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 initialization,
+         * 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);
+                /* This call will also set host->clk_gated to false */
+                mmc_set_clock(host, host->clk_old);
+        }
+}
+
+void mmc_set_ungated(struct mmc_host *host)
+{
+        unsigned long flags;
+
+        /*
+         * We've been given a new frequency while the clock is gated,
+         * so make sure we regard this as ungating it.
+         */
+        spin_lock_irqsave(&host->clk_lock, flags);
+        host->clk_gated = false;
+        spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
+#else
+void mmc_set_ungated(struct mmc_host *host)
+{
+}
+#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 77240cd11bcf..026c975b99a9 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -33,6 +33,9 @@ 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_ungated(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 eed1405fd742..998797ed67a6 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 10b8af27e03a..92e33703e437 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
@@ -20,6 +21,7 @@
 #include <linux/suspend.h>
 
 #include <linux/mmc/host.h>
+#include <linux/mmc/card.h>
 
 #include "core.h"
 #include "host.h"
@@ -50,6 +52,204 @@ 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;
+
+        if (!freq) {
+                pr_debug("%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);
+
+        /*
+         * Delay n bus cycles (at least 8 from MMC spec) before attempting
+         * to disable the MCI block clock. The reference count may have
+         * gone up again after this delay due to rescheduling!
+         */
+        if (!host->clk_requests) {
+                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 */
+                spin_unlock_irqrestore(&host->clk_lock, flags);
+                return;
+        }
+        mutex_lock(&host->clk_gate_mutex);
+        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: gated MCI clock\n", mmc_hostname(host));
+        }
+        spin_unlock_irqrestore(&host->clk_lock, flags);
+        mutex_unlock(&host->clk_gate_mutex);
+}
+
+/*
+ * 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_gate_work);
+
+        mmc_host_clk_gate_delayed(host);
+}
+
+/**
+ *      mmc_host_clk_ungate - ungate hardware MCI clocks
+ *      @host: host to ungate.
+ *
+ *      Makes sure the host ios.clock is restored to a non-zero value
+ *      past this call. Increase clock reference count and ungate clock
+ *      if we're the first user.
+ */
+void mmc_host_clk_ungate(struct mmc_host *host)
+{
+        unsigned long flags;
+
+        mutex_lock(&host->clk_gate_mutex);
+        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);
+        mutex_unlock(&host->clk_gate_mutex);
+}
+
+/**
+ *      mmc_host_may_gate_card - check if this card may be gated
+ *      @card: card to check.
+ */
+static bool mmc_host_may_gate_card(struct mmc_card *card)
+{
+        /* If there is no card we may gate it */
+        if (!card)
+                return true;
+        /*
+         * Don't gate SDIO cards! These need to be clocked at all times
+         * since they may be independent systems generating interrupts
+         * and other events. The clock requests counter from the core will
+         * go down to zero since the core does not need it, but we will not
+         * gate the clock, because there is somebody out there that may still
+         * be using it.
+         */
+        if (mmc_card_sdio(card))
+                return false;
+
+        return true;
+}
+
+/**
+ *      mmc_host_clk_gate - gate off hardware MCI clocks
+ *      @host: host to gate.
+ *
+ *      Calls the host driver with ios.clock set to zero as often as possible
+ *      in order to gate off hardware MCI clocks. Decrease clock reference
+ *      count and schedule disabling 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 (mmc_host_may_gate_card(host->card) &&
+            !host->clk_requests)
+                schedule_work(&host->clk_gate_work);
+        spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
+/**
+ *      mmc_host_clk_rate - get current clock frequency setting
+ *      @host: host to get the clock frequency for.
+ *
+ *      Returns current clock frequency regardless of gating.
+ */
+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 clock to control
+ */
+static inline void mmc_host_clk_init(struct mmc_host *host)
+{
+        host->clk_requests = 0;
+        /* Hold MCI clock for 8 cycles by default */
+        host->clk_delay = 8;
+        host->clk_gated = false;
+        INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
+        spin_lock_init(&host->clk_lock);
+        mutex_init(&host->clk_gate_mutex);
+}
+
+/**
+ *      mmc_host_clk_exit - shut down clock gating code
+ *      @host: host with potential clock to control
+ */
+static inline void mmc_host_clk_exit(struct mmc_host *host)
+{
+        /*
+         * Wait for any outstanding gate and then make sure we're
+         * ungated before exiting.
+         */
+        if (cancel_work_sync(&host->clk_gate_work))
+                mmc_host_clk_gate_delayed(host);
+        if (host->clk_gated)
+                mmc_host_clk_ungate(host);
+        BUG_ON(host->clk_requests > 0);
+}
+
+#else
+
+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 +282,8 @@ 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 +365,8 @@ 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 +387,3 @@ 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 8c87e1109a34..de199f911928 100644
--- a/drivers/mmc/core/host.h
+++ b/drivers/mmc/core/host.h
@@ -10,10 +10,31 @@
  */
 #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);
 
+#ifdef CONFIG_MMC_CLKGATE
+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);
+
+#else
+static inline void mmc_host_clk_ungate(struct mmc_host *host)
+{
+}
+
+static inline void mmc_host_clk_gate(struct mmc_host *host)
+{
+}
+
+static inline unsigned int mmc_host_clk_rate(struct mmc_host *host)
+{
+        return host->ios.clock;
+}
+#endif
+
 void mmc_host_deeper_disable(struct work_struct *work);
 
 #endif
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 30f6fad99a58..381c77fd4dca 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -172,6 +172,16 @@ 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 */
+        struct work_struct      clk_gate_work; /* delayed clock gate */
+        unsigned int            clk_old;        /* old clock value cache */
+        spinlock_t              clk_lock;       /* lock for clk fields */
+        struct mutex            clk_gate_mutex; /* mutex for clock gating */
+#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 */