sdio: introduce API for special power management features

This patch series provides the core changes needed to allow SDIO cards to
remain powered and active while the host system is suspended, and let them
wake up the host system when needed.  This is used to implement
wake-on-lan with SDIO wireless cards at the moment.  Patches to add that
support to the libertas driver will be posted separately.

This patch:

Some SDIO cards have the ability to keep on running autonomously when the
host system is suspended, and wake it up when needed.  This however
requires that the host controller preserve power to the card, and
configure itself appropriately for wake-up.

There is however 4 layers of abstractions involved: the host controller
driver, the MMC core code, the SDIO card management code, and the actual
SDIO function driver.  To make things simple and manageable, host drivers
must advertise their PM capabilities with a feature bitmask, then function
drivers can query and set those features from their suspend method.  Then
each layer in the suspend call chain is expected to act upon those bits
accordingly.

[akpm@linux-foundation.org: fix typo in comment]
Signed-off-by: Nicolas Pitre <nico@marvell.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 58 insertions, 3 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 30acd5265821..f4b97d3c3d0f 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1151,6 +1151,9 @@ void mmc_stop_host(struct mmc_host *host)
         cancel_delayed_work(&host->detect);
         mmc_flush_scheduled_work();
 
+        /* clear pm flags now and let card drivers set them as needed */
+        host->pm_flags = 0;
+
         mmc_bus_get(host);
         if (host->bus_ops && !host->bus_dead) {
                 if (host->bus_ops->remove)
@@ -1273,12 +1276,13 @@ int mmc_suspend_host(struct mmc_host *host, pm_message_t state)
                         mmc_claim_host(host);
                         mmc_detach_bus(host);
                         mmc_release_host(host);
+                        host->pm_flags = 0;
                         err = 0;
                 }
         }
         mmc_bus_put(host);
 
-        if (!err)
+        if (!err && !(host->pm_flags & MMC_PM_KEEP_POWER))
                 mmc_power_off(host);
 
         return err;
@@ -1296,8 +1300,10 @@ int mmc_resume_host(struct mmc_host *host)
 
         mmc_bus_get(host);
         if (host->bus_ops && !host->bus_dead) {
-                mmc_power_up(host);
-                mmc_select_voltage(host, host->ocr);
+                if (!(host->pm_flags & MMC_PM_KEEP_POWER)) {
+                        mmc_power_up(host);
+                        mmc_select_voltage(host, host->ocr);
+                }
                 BUG_ON(!host->bus_ops->resume);
                 err = host->bus_ops->resume(host);
                 if (err) {
diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
index 87c618904ee2..ff27c8c71355 100644
--- a/drivers/mmc/core/sdio_io.c
+++ b/drivers/mmc/core/sdio_io.c
@@ -640,3 +640,52 @@ void sdio_f0_writeb(struct sdio_func *func, unsigned char b, unsigned int addr,
                 *err_ret = ret;
 }
 EXPORT_SYMBOL_GPL(sdio_f0_writeb);
+
+/**
+ *      sdio_get_host_pm_caps - get host power management capabilities
+ *      @func: SDIO function attached to host
+ *
+ *      Returns a capability bitmask corresponding to power management
+ *      features supported by the host controller that the card function
+ *      might rely upon during a system suspend.  The host doesn't need
+ *      to be claimed, nor the function active, for this information to be
+ *      obtained.
+ */
+mmc_pm_flag_t sdio_get_host_pm_caps(struct sdio_func *func)
+{
+        BUG_ON(!func);
+        BUG_ON(!func->card);
+
+        return func->card->host->pm_caps;
+}
+EXPORT_SYMBOL_GPL(sdio_get_host_pm_caps);
+
+/**
+ *      sdio_set_host_pm_flags - set wanted host power management capabilities
+ *      @func: SDIO function attached to host
+ *
+ *      Set a capability bitmask corresponding to wanted host controller
+ *      power management features for the upcoming suspend state.
+ *      This must be called, if needed, each time the suspend method of
+ *      the function driver is called, and must contain only bits that
+ *      were returned by sdio_get_host_pm_caps().
+ *      The host doesn't need to be claimed, nor the function active,
+ *      for this information to be set.
+ */
+int sdio_set_host_pm_flags(struct sdio_func *func, mmc_pm_flag_t flags)
+{
+        struct mmc_host *host;
+
+        BUG_ON(!func);
+        BUG_ON(!func->card);
+
+        host = func->card->host;
+
+        if (flags & ~host->pm_caps)
+                return -EINVAL;
+
+        /* function suspend methods are serialized, hence no lock needed */
+        host->pm_flags |= flags;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(sdio_set_host_pm_flags);