linux-kernel - [PATCH 1/2] mmc: add functions to enable/disable aggressive clock gating

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Message-Id: <e13e177c732ee8ad2d6fe389c9bac21877f60c59.1313400777.git.mika.westerberg@linux.intel.com>
Date:	Mon, 15 Aug 2011 13:03:37 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	linux-mmc@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, cjb@...top.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 1/2] mmc: add functions to enable/disable aggressive clock gating

There are few places where we want to make sure that no clock gating takes
place. For example when we are updating several related fields in ios
structure and we don't want to accidentally pass the partially filled ios
to the host driver.

To solve this we add two functions to enable/disable the aggressive clock
gating where this is needed.

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
---
 drivers/mmc/core/host.c  |   39 ++++++++++++++++++++++++++++++++++++++-
 drivers/mmc/core/host.h  |   11 +++++++++++
 include/linux/mmc/host.h |    1 +
 3 files changed, 50 insertions(+), 1 deletions(-)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index b29d3e8..ee52246 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -178,7 +178,7 @@ void mmc_host_clk_gate(struct mmc_host *host)
 	spin_lock_irqsave(&host->clk_lock, flags);
 	host->clk_requests--;
 	if (mmc_host_may_gate_card(host->card) &&
-	    !host->clk_requests)
+	    !host->clk_requests && !host->clk_disabled)
 		schedule_work(&host->clk_gate_work);
 	spin_unlock_irqrestore(&host->clk_lock, flags);
 }
@@ -204,6 +204,42 @@ unsigned int mmc_host_clk_rate(struct mmc_host *host)
 }
 
 /**
+ *	mmc_host_clk_gate_disable - temporarily disable clock gating
+ *	@host: host to disable clock gating
+ *
+ *	Function temporarily disables aggressive clock gating. This is to
+ *	prevent clock gating worker to kick in for example in a middle of
+ *	ios structure update.
+ *
+ *	After this function returns, it is guaranteed that no clock gating
+ *	takes place until it is re-enabled again.
+ */
+void mmc_host_clk_gate_disable(struct mmc_host *host)
+{
+	spin_lock_irq(&host->clk_lock);
+	WARN_ON(host->clk_disabled);
+	host->clk_disabled = true;
+	spin_unlock_irq(&host->clk_lock);
+
+	cancel_work_sync(&host->clk_gate_work);
+}
+
+/**
+ *	mmc_host_clk_gate_enable - re-enables clock gating
+ *	@host: host to re-enable clock gating
+ *
+ *	Allows aggressive clock gating framework to continue gating the
+ *	host clock.
+ */
+void mmc_host_clk_gate_enable(struct mmc_host *host)
+{
+	spin_lock_irq(&host->clk_lock);
+	WARN_ON(!host->clk_disabled);
+	host->clk_disabled = false;
+	spin_unlock_irq(&host->clk_lock);
+}
+
+/**
  *	mmc_host_clk_init - set up clock gating code
  *	@host: host with potential clock to control
  */
@@ -213,6 +249,7 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
 	/* Hold MCI clock for 8 cycles by default */
 	host->clk_delay = 8;
 	host->clk_gated = false;
+	host->clk_disabled = false;
 	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
 	spin_lock_init(&host->clk_lock);
 	mutex_init(&host->clk_gate_mutex);
diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
index de199f9..7148b24 100644
--- a/drivers/mmc/core/host.h
+++ b/drivers/mmc/core/host.h
@@ -19,6 +19,8 @@ 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_clk_gate_disable(struct mmc_host *host);
+void mmc_host_clk_gate_enable(struct mmc_host *host);
 
 #else
 static inline void mmc_host_clk_ungate(struct mmc_host *host)
@@ -33,6 +35,15 @@ static inline unsigned int mmc_host_clk_rate(struct mmc_host *host)
 {
 	return host->ios.clock;
 }
+
+static inline void mmc_host_clk_gate_disable(struct mmc_host *host)
+{
+}
+
+static inline void mmc_host_clk_gate_enable(struct mmc_host *host)
+{
+}
+
 #endif
 
 void mmc_host_deeper_disable(struct work_struct *work);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 1d09562..dea6350 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -240,6 +240,7 @@ struct mmc_host {
 	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 */
+	bool			clk_disabled;	/* gating is temporarily disabled */
 #endif
 
 	/* host specific block data */
-- 
1.7.5.4

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