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 <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/core/host.c

···
 
 #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.
···
 #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.

drivers/mmc/core/host.h

···
 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
 

include/linux/mmc/host.h

···
 
 #include <linux/leds.h>
 #include <linux/mutex.h>
+#include <linux/timer.h>
 #include <linux/sched.h>
 #include <linux/device.h>
 #include <linux/fault-inject.h>
···
 #ifdef CONFIG_MMC_DEBUG
 	unsigned int		removed:1;	/* host is being removed */
 #endif
+	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			rescan_disable;	/* disable card detection */
 	int			rescan_entered;	/* used with nonremovable devices */
+
+	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 */
 
 	bool			trigger_card_event; /* card_event necessary */
 
···
 static inline bool mmc_card_hs400(struct mmc_card *card)
 {
 	return card->host->ios.timing == MMC_TIMING_MMC_HS400;
+}
+
+void mmc_retune_timer_stop(struct mmc_host *host);
+
+static inline void mmc_retune_needed(struct mmc_host *host)
+{
+	if (host->can_retune)
+		host->need_retune = 1;
+}
+
+static inline void mmc_retune_recheck(struct mmc_host *host)
+{
+	if (host->hold_retune <= 1)
+		host->retune_now = 1;
 }
 
 #endif /* LINUX_MMC_HOST_H */