mmc: add support for card-detection polling

Some hosts (and boards that use mmc_spi) do not use interrupts on the CD
line, so they can't trigger mmc_detect_change. We want to poll the card
and see if there was a change. 1 second poll interval seems resonable.

This patch also implements .get_cd() host operation, that could be used
by the hosts that are able to report card-detect status without need to
talk MMC.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

2 files changed, 20 insertions, 3 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 01ced4c5a61d..ede5d1e2e20d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -638,6 +638,9 @@ void mmc_rescan(struct work_struct *work)
                  */
                 mmc_bus_put(host);
 
+                if (host->ops->get_cd && host->ops->get_cd(host) == 0)
+                        goto out;
+
                 mmc_claim_host(host);
 
                 mmc_power_up(host);
@@ -652,7 +655,7 @@ void mmc_rescan(struct work_struct *work)
                 if (!err) {
                         if (mmc_attach_sdio(host, ocr))
                                 mmc_power_off(host);
-                        return;
+                        goto out;
                 }
 
                 /*
@@ -662,7 +665,7 @@ void mmc_rescan(struct work_struct *work)
                 if (!err) {
                         if (mmc_attach_sd(host, ocr))
                                 mmc_power_off(host);
-                        return;
+                        goto out;
                 }
 
                 /*
@@ -672,7 +675,7 @@ void mmc_rescan(struct work_struct *work)
                 if (!err) {
                         if (mmc_attach_mmc(host, ocr))
                                 mmc_power_off(host);
-                        return;
+                        goto out;
                 }
 
                 mmc_release_host(host);
@@ -683,6 +686,9 @@ void mmc_rescan(struct work_struct *work)
 
                 mmc_bus_put(host);
         }
+out:
+        if (host->caps & MMC_CAP_NEEDS_POLL)
+                mmc_schedule_delayed_work(&host->detect, HZ);
 }
 
 void mmc_start_host(struct mmc_host *host)
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 7ab962fa1d73..6188e19d2331 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -51,8 +51,18 @@ struct mmc_ios {
 
 struct mmc_host_ops {
         void    (*request)(struct mmc_host *host, struct mmc_request *req);
+        /*
+         * Avoid calling these three functions too often or in a "fast path",
+         * since underlaying controller might implement them in an expensive
+         * and/or slow way.
+         *
+         * Also note that these functions might sleep, so don't call them
+         * in the atomic contexts!
+         */
         void    (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
         int     (*get_ro)(struct mmc_host *host);
+        int     (*get_cd)(struct mmc_host *host);
+
         void    (*enable_sdio_irq)(struct mmc_host *host, int enable);
 };
 
@@ -94,6 +104,7 @@ struct mmc_host {
 #define MMC_CAP_SD_HIGHSPEED    (1 << 3)        /* Can do SD high-speed timing */
 #define MMC_CAP_SDIO_IRQ        (1 << 4)        /* Can signal pending SDIO IRQs */
 #define MMC_CAP_SPI             (1 << 5)        /* Talks only SPI protocols */
+#define MMC_CAP_NEEDS_POLL      (1 << 6)        /* Needs polling for card-detection */
 
         /* host specific block data */
         unsigned int            max_seg_size;   /* see blk_queue_max_segment_size */