mtd: maps: sa1100-flash: Add reference counter to set_vpp()

This patch is part of a set which fixes unnecessary flash erase and write errors
resulting from the MTD CFI driver turning off vpp while an erase is in progress.
This patch allows sa1100_set_vpp() calls to be nested by adding a reference
counter.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/mtd/maps/sa1100-flash.c b/drivers/mtd/maps/sa1100-flash.c
index cbc3b7867910..1eaf7b6c35e5 100644
--- a/drivers/mtd/maps/sa1100-flash.c
+++ b/drivers/mtd/maps/sa1100-flash.c
@@ -36,10 +36,22 @@ struct sa_info {
         struct sa_subdev_info   subdev[0];
 };
 
+static DEFINE_SPINLOCK(sa1100_vpp_lock);
+static int sa1100_vpp_refcnt;
 static void sa1100_set_vpp(struct map_info *map, int on)
 {
         struct sa_subdev_info *subdev = container_of(map, struct sa_subdev_info, map);
-        subdev->plat->set_vpp(on);
+        unsigned long flags;
+
+        spin_lock_irqsave(&sa1100_vpp_lock, flags);
+        if (on) {
+                if (++sa1100_vpp_refcnt == 1)   /* first nested 'on' */
+                        subdev->plat->set_vpp(1);
+        } else {
+                if (--sa1100_vpp_refcnt == 0)   /* last nested 'off' */
+                        subdev->plat->set_vpp(0);
+        }
+        spin_unlock_irqrestore(&sa1100_vpp_lock, flags);
 }
 
 static void sa1100_destroy_subdev(struct sa_subdev_info *subdev)