mtd: maps: pcmciamtd: 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 pcmciamtd_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, 12 insertions, 1 deletions

diff --git a/drivers/mtd/maps/pcmciamtd.c b/drivers/mtd/maps/pcmciamtd.c
index e8e9fec23553..7d5cf369f0ad 100644
--- a/drivers/mtd/maps/pcmciamtd.c
+++ b/drivers/mtd/maps/pcmciamtd.c
@@ -295,13 +295,24 @@ static void pcmcia_copy_to(struct map_info *map, unsigned long to, const void *f
 }
 
 
+static DEFINE_SPINLOCK(pcmcia_vpp_lock);
+static int pcmcia_vpp_refcnt;
 static void pcmciamtd_set_vpp(struct map_info *map, int on)
 {
         struct pcmciamtd_dev *dev = (struct pcmciamtd_dev *)map->map_priv_1;
         struct pcmcia_device *link = dev->p_dev;
+        unsigned long flags;
 
         pr_debug("dev = %p on = %d vpp = %d\n\n", dev, on, dev->vpp);
-        pcmcia_fixup_vpp(link, on ? dev->vpp : 0);
+        spin_lock_irqsave(&pcmcia_vpp_lock, flags);
+        if (on) {
+                if (++pcmcia_vpp_refcnt == 1)   /* first nested 'on' */
+                        pcmcia_fixup_vpp(link, dev->vpp);
+        } else {
+                if (--pcmcia_vpp_refcnt == 0)   /* last nested 'off' */
+                        pcmcia_fixup_vpp(link, 0);
+        }
+        spin_unlock_irqrestore(&pcmcia_vpp_lock, flags);
 }