@@ -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.
@@ -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 +617,12 @@ static inline void mmc_set_ios(struct mmc_host *host)
ios->power_mode, ios->chip_select, ios->vdd,
ios->bus_width, ios->timing);
+ /*
+ * We get a new frequency while the clock is gated,
+ * so make sure we regard this as ungating it.
+ */
+ if (ios->clock > 0 && host->clk_gated)
+ host->clk_gated = false;
host->ops->set_ios(host, ios);
}
@@ -641,6 +650,40 @@ 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.
*/
@@ -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,
@@ -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:
@@ -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 +52,206 @@ 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 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 (!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: gated 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_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 - 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 (mmc_host_may_gate_card(host->card) &&
+ !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 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 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_disable_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 +284,8 @@ 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 +367,8 @@ 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 +389,3 @@ void mmc_free_host(struct mmc_host *host)
}
EXPORT_SYMBOL(mmc_free_host);
-
@@ -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
@@ -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 */