mmc: core: Add deferred bus resume policy.

A card driver can now specify that the underlying bus should *not*
auto-resume with the rest of the system. This is useful for reducing resume
latency as well as saving power when the card driver is not using the
bus. In the future, we'll add support for manual suspend

Signed-off-by: San Mehat <san@google.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 5db69d8849d..265a8c09f7d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1594,6 +1594,30 @@ static inline void mmc_bus_put(struct mmc_host *host)
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
+int mmc_resume_bus(struct mmc_host *host)
+{
+	if (!mmc_bus_needs_resume(host))
+		return -EINVAL;
+
+	printk("%s: Starting deferred resume\n", mmc_hostname(host));
+	host->bus_resume_flags &= ~MMC_BUSRESUME_NEEDS_RESUME;
+	mmc_bus_get(host);
+	if (host->bus_ops && !host->bus_dead) {
+		mmc_power_up(host);
+		BUG_ON(!host->bus_ops->resume);
+		host->bus_ops->resume(host);
+	}
+
+	if (host->bus_ops->detect && !host->bus_dead)
+		host->bus_ops->detect(host);
+
+	mmc_bus_put(host);
+	printk("%s: Deferred resume completed\n", mmc_hostname(host));
+	return 0;
+}
+
+EXPORT_SYMBOL(mmc_resume_bus);
+
 /*
  * Assign a mmc bus handler to a host. Only one bus handler may control a
  * host at any given time.
@@ -2638,6 +2662,9 @@ int mmc_suspend_host(struct mmc_host *host)
 {
 	int err = 0;
 
+	if (mmc_bus_needs_resume(host))
+		return 0;
+
 	cancel_delayed_work(&host->detect);
 	mmc_flush_scheduled_work();
 
@@ -2689,6 +2716,12 @@ int mmc_resume_host(struct mmc_host *host)
 	int err = 0;
 
 	mmc_bus_get(host);
+	if (host->bus_resume_flags & MMC_BUSRESUME_MANUAL_RESUME) {
+		host->bus_resume_flags |= MMC_BUSRESUME_NEEDS_RESUME;
+		mmc_bus_put(host);
+		return 0;
+	}
+
 	if (host->bus_ops && !host->bus_dead) {
 		if (!mmc_card_keep_power(host)) {
 			mmc_power_up(host);