[PATCH RESEND] sdhci-clk-gating-support

[PATCH RESEND] sdhci-clk-gating-support

[MADHAV SINGHCHAUHAN]

I fixed the all issues after running checkpatch.pl and resending it.

From 1fae693a2eef37d878066b09c89f95f57f945f64 Mon Sep 17 00:00:00 2001
From: Madhav Singh <singh.madhav@samsung.com>
Date: Fri, 2 Jul 2010 19:33:19 +0530
Subject: [PATCH] sdhci-clk-gating-support
 This patch implements clock gating support in sdhci layer.It will enable the clock when
 host controller start sending request to attached device and will disable it once it
 finish the command.

Signed-off-by: Madhav Chauhan <singh.madhav@samsung.com> , Nitish Ambastha <nitish.a@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 drivers/mmc/host/sdhci.c |   34 ++++++++++++++++++++++++++++++++++
 drivers/mmc/host/sdhci.h |    7 +++++++
 2 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index c6d1bd8..37ed265 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1103,6 +1103,8 @@ static void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
 
 	spin_lock_irqsave(&host->lock, flags);
 
+	sdhci_clk_enable(host);	/*Enable clock as transfer starts now*/
+
 	WARN_ON(host->mrq != NULL);
 
 #ifndef SDHCI_USE_LEDS_CLASS
@@ -1310,6 +1312,8 @@ static void sdhci_tasklet_finish(unsigned long param)
 		sdhci_reset(host, SDHCI_RESET_DATA);
 	}
 
+	sdhci_clk_disable(host);	/*Disable clock as command has been processed*/
+
 	host->mrq = NULL;
 	host->cmd = NULL;
 	host->data = NULL;
@@ -1597,6 +1601,8 @@ int sdhci_suspend_host(struct sdhci_host *host, pm_message_t state)
 
 	sdhci_disable_card_detection(host);
 
+	sdhci_clk_enable(host);	/* Enable clock */
+
 	ret = mmc_suspend_host(host->mmc);
 	if (ret)
 		return ret;
@@ -1626,6 +1632,9 @@ int sdhci_resume_host(struct sdhci_host *host)
 	mmiowb();
 
 	ret = mmc_resume_host(host->mmc);
+
+	sdhci_clk_disable(host);	/*Now device has wake up disable it*/
+
 	sdhci_enable_card_detection(host);
 
 	return ret;
@@ -1654,6 +1663,9 @@ struct sdhci_host *sdhci_alloc_host(struct device *dev,
 		return ERR_PTR(-ENOMEM);
 
 	host = mmc_priv(mmc);
+	host->user = 0;		/*For Clock gating*/
+	host->clk_restore = 0;
+
 	host->mmc = mmc;
 
 	return host;
@@ -1984,6 +1996,28 @@ void sdhci_free_host(struct sdhci_host *host)
 
 EXPORT_SYMBOL_GPL(sdhci_free_host);
 
+void sdhci_clk_enable(struct sdhci_host *host)
+{
+	if (!host->user) {
+		if (host->clk_restore && host->clock == 0)
+			sdhci_set_clock(host, host->clk_restore);
+	}
+	host->user++;
+}
+EXPORT_SYMBOL_GPL(sdhci_clk_enable);
+
+void sdhci_clk_disable(struct sdhci_host *host)
+{
+	host->user--;
+	if (!host->user)
+		if (host->clock != 0) {
+			host->clk_restore = host->clock;
+			sdhci_set_clock(host, 0);
+		}
+}
+EXPORT_SYMBOL_GPL(sdhci_clk_disable);
+
+
 /*****************************************************************************\
  *                                                                           *
  * Driver init/exit                                                          *
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index c846813..5912e28 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -292,6 +292,9 @@ struct sdhci_host {
 
 	struct timer_list	timer;		/* Timer for timeouts */
 
+	unsigned int		clk_restore;	/*For Clock Gating*/
+	unsigned int		user;
+
 	unsigned long		private[0] ____cacheline_aligned;
 };
 
@@ -410,6 +413,10 @@ static inline void *sdhci_priv(struct sdhci_host *host)
 extern int sdhci_add_host(struct sdhci_host *host);
 extern void sdhci_remove_host(struct sdhci_host *host, int dead);
 
+/*For Clock Gating*/
+extern void sdhci_clk_enable(struct sdhci_host *host);
+extern void sdhci_clk_disable(struct sdhci_host *host);
+
 #ifdef CONFIG_PM
 extern int sdhci_suspend_host(struct sdhci_host *host, pm_message_t state);
 extern int sdhci_resume_host(struct sdhci_host *host);
-- 
1.6.0.4
 
 

Re: [PATCH RESEND] sdhci-clk-gating-support

[Chris Ball]

Hi Madhav,

> +       host->user = 0;         /*For Clock gating*/
> +       host->clk_restore = 0;

Also, it's not obvious to me why two variables are necessary.  What's
wrong with just setting host->clk_restore when disabling clock, and
testing whether it's non-zero instead of testing host->user?
(host->user would need a more descriptive name, too.)

Thanks,

- Chris.
-- 
Chris Ball   <cjb@laptop.org>
One Laptop Per Child

Re: [PATCH RESEND] sdhci-clk-gating-support

[Madhav]

> Hi Madhav,
>
>> +       host->user = 0;         /*For Clock gating*/
>> +       host->clk_restore = 0;
> Also, it's not obvious to me why two variables are necessary.  What's
> wrong with just setting host->clk_restore when disabling clock, and
> testing whether it's non-zero instead of testing host->user?
> (host->user would need a more descriptive name, too.)
we used host->user for making enable disable in a proper sequence i.e. 
enable-disable-enable and
were facing some issues as we were using workqueue.So in current version we 
tested the patch
without host->user and it works fine so we can remove it.
>Some general points:
> * have you measured whether there's a performance impact from
>   bringing the clock up and down for every request?
I will test  this and update you soon.
> * I'd expect this to be implemented as an MMC capability, so
>   that it can be avoided on specific controllers.
Yes we can do this just we need to add one macro for clock gating capability 
in struct mmc_host  and
also looking for any other  good alternative  for the same. Do we have such 
host controllers for them we
should avoid this??

>
> Thanks,
>
> - Chris.
> -- 
> Chris Ball   <cjb@laptop.org>
> One Laptop Per Child