mmc: host: Add facility to support re-tuning

Currently, there is core support for tuning during
initialization. There can also be a need to re-tune
periodically (e.g. sdhci) or to re-tune after the
host controller is powered off (e.g. after PM
runtime suspend / resume) or to re-tune in response
to CRC errors.

The main requirements for re-tuning are:
  - ability to enable / disable re-tuning
  - ability to flag that re-tuning is needed
  - ability to re-tune before any request
  - ability to hold off re-tuning if the card is busy
  - ability to hold off re-tuning if re-tuning is in
  progress
  - ability to run a re-tuning timer

To support those requirements 7 members are added to struct
mmc_host:

  unsigned int		can_retune:1;	/* re-tuning can be used */
  unsigned int		doing_retune:1;	/* re-tuning in progress */
  unsigned int		retune_now:1;   /* do re-tuning at next req */
  int			need_retune;	/* re-tuning is needed */
  int			hold_retune;	/* hold off re-tuning */
  unsigned int		retune_period;  /* re-tuning period in secs */
  struct timer_list	retune_timer;	/* for periodic re-tuning */

need_retune is an integer so it can be set without needing
synchronization. hold_retune is a integer to allow nesting.

Various simple functions are provided to set / clear those
variables.

Subsequent patches take those functions into use.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

2 files changed, 74 insertions, 0 deletions

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 8be0df758e68..e90e02fc596a 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -301,6 +301,73 @@ static inline void mmc_host_clk_sysfs_init(struct mmc_host *host)
 
 #endif
 
+void mmc_retune_enable(struct mmc_host *host)
+{
+	host->can_retune = 1;
+	if (host->retune_period)
+		mod_timer(&host->retune_timer,
+			  jiffies + host->retune_period * HZ);
+}
+
+void mmc_retune_disable(struct mmc_host *host)
+{
+	host->can_retune = 0;
+	del_timer_sync(&host->retune_timer);
+	host->retune_now = 0;
+	host->need_retune = 0;
+}
+
+void mmc_retune_timer_stop(struct mmc_host *host)
+{
+	del_timer_sync(&host->retune_timer);
+}
+EXPORT_SYMBOL(mmc_retune_timer_stop);
+
+void mmc_retune_hold(struct mmc_host *host)
+{
+	if (!host->hold_retune)
+		host->retune_now = 1;
+	host->hold_retune += 1;
+}
+
+void mmc_retune_release(struct mmc_host *host)
+{
+	if (host->hold_retune)
+		host->hold_retune -= 1;
+	else
+		WARN_ON(1);
+}
+
+int mmc_retune(struct mmc_host *host)
+{
+	int err;
+
+	if (host->retune_now)
+		host->retune_now = 0;
+	else
+		return 0;
+
+	if (!host->need_retune || host->doing_retune || !host->card)
+		return 0;
+
+	host->need_retune = 0;
+
+	host->doing_retune = 1;
+
+	err = mmc_execute_tuning(host->card);
+
+	host->doing_retune = 0;
+
+	return err;
+}
+
+static void mmc_retune_timer(unsigned long data)
+{
+	struct mmc_host *host = (struct mmc_host *)data;
+
+	mmc_retune_needed(host);
+}
+
 /**
  *	mmc_of_parse() - parse host's device-tree node
  *	@host: host whose node should be parsed.
@@ -504,6 +571,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 #ifdef CONFIG_PM
 	host->pm_notify.notifier_call = mmc_pm_notify;
 #endif
+	setup_timer(&host->retune_timer, mmc_retune_timer, (unsigned long)host);
 
 	/*
 	 * By default, hosts do not support SGIO or large requests.
diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
index f2ab9e578126..992bf5397633 100644
--- a/drivers/mmc/core/host.h
+++ b/drivers/mmc/core/host.h
@@ -15,5 +15,11 @@
 int mmc_register_host_class(void);
 void mmc_unregister_host_class(void);
 
+void mmc_retune_enable(struct mmc_host *host);
+void mmc_retune_disable(struct mmc_host *host);
+void mmc_retune_hold(struct mmc_host *host);
+void mmc_retune_release(struct mmc_host *host);
+int mmc_retune(struct mmc_host *host);
+
 #endif