mmc: allow host claim / release nesting

This change allows the MMC host to be claimed in situations where the host
may or may not have already been claimed.  Also 'mmc_try_claim_host()' is
now exported.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Acked-by: Matt Fleming <matt@console-pimps.org>
Cc: Ian Molton <ian@mnementh.co.uk>
Cc: "Roberto A. Foglietta" <roberto.foglietta@gmail.com>
Cc: Jarkko Lavinen <jarkko.lavinen@nokia.com>
Cc: Denis Karpov <ext-denis.2.karpov@nokia.com>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Philip Langdale <philipl@overt.org>
Cc: "Madhusudhan" <madhu.cr@ti.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>

3 files changed, 28 insertions, 9 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index fb24a096dba8..02f2b1871a38 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -461,16 +461,18 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
         while (1) {
                 set_current_state(TASK_UNINTERRUPTIBLE);
                 stop = abort ? atomic_read(abort) : 0;
-                if (stop || !host->claimed)
+                if (stop || !host->claimed || host->claimer == current)
                         break;
                 spin_unlock_irqrestore(&host->lock, flags);
                 schedule();
                 spin_lock_irqsave(&host->lock, flags);
         }
         set_current_state(TASK_RUNNING);
-        if (!stop)
+        if (!stop) {
                 host->claimed = 1;
-        else
+                host->claimer = current;
+                host->claim_cnt += 1;
+        } else
                 wake_up(&host->wq);
         spin_unlock_irqrestore(&host->lock, flags);
         remove_wait_queue(&host->wq, &wait);
@@ -481,29 +483,43 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
 
 EXPORT_SYMBOL(__mmc_claim_host);
 
-static int mmc_try_claim_host(struct mmc_host *host)
+/**
+ *      mmc_try_claim_host - try exclusively to claim a host
+ *      @host: mmc host to claim
+ *
+ *      Returns %1 if the host is claimed, %0 otherwise.
+ */
+int mmc_try_claim_host(struct mmc_host *host)
 {
         int claimed_host = 0;
         unsigned long flags;
 
         spin_lock_irqsave(&host->lock, flags);
-        if (!host->claimed) {
+        if (!host->claimed || host->claimer == current) {
                 host->claimed = 1;
+                host->claimer = current;
+                host->claim_cnt += 1;
                 claimed_host = 1;
         }
         spin_unlock_irqrestore(&host->lock, flags);
         return claimed_host;
 }
+EXPORT_SYMBOL(mmc_try_claim_host);
 
 static void mmc_do_release_host(struct mmc_host *host)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&host->lock, flags);
-        host->claimed = 0;
-        spin_unlock_irqrestore(&host->lock, flags);
-
-        wake_up(&host->wq);
+        if (--host->claim_cnt) {
+                /* Release for nested claim */
+                spin_unlock_irqrestore(&host->lock, flags);
+        } else {
+                host->claimed = 0;
+                host->claimer = NULL;
+                spin_unlock_irqrestore(&host->lock, flags);
+                wake_up(&host->wq);
+        }
 }
 
 void mmc_host_deeper_disable(struct work_struct *work)
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 7ac8b500d55c..e4898e9eeb59 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -139,6 +139,7 @@ extern unsigned int mmc_align_data_size(struct mmc_card *, unsigned int);
 
 extern int __mmc_claim_host(struct mmc_host *host, atomic_t *abort);
 extern void mmc_release_host(struct mmc_host *host);
+extern int mmc_try_claim_host(struct mmc_host *host);
 
 /**
  *      mmc_claim_host - exclusively claim a host
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 338a9b3d51e4..631a2fea5264 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -182,6 +182,8 @@ struct mmc_host {
         struct mmc_card         *card;          /* device attached to this host */
 
         wait_queue_head_t       wq;
+        struct task_struct      *claimer;       /* task that has host claimed */
+        int                     claim_cnt;      /* "claim" nesting count */
 
         struct delayed_work     detect;