mtd: maps: l440gx: Add reference counter to set_vpp()

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=5fbabf3f45a15c2b39170980cee01368138f4d79
Commit:     5fbabf3f45a15c2b39170980cee01368138f4d79
Parent:     876fe76d793d03077eb61ba3afab4a383f46c554
Author:     Paul Parsons <lost.distance at yahoo.com>
AuthorDate: Wed Mar 7 14:12:50 2012 +0000
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Tue Mar 27 00:52:49 2012 +0100

    mtd: maps: l440gx: 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 l440gx_set_vpp() calls to be nested by adding a reference
    counter.
    
    Signed-off-by: Paul Parsons <lost.distance at yahoo.com>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/maps/l440gx.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/maps/l440gx.c b/drivers/mtd/maps/l440gx.c
index dd0360b..74bd98e 100644
--- a/drivers/mtd/maps/l440gx.c
+++ b/drivers/mtd/maps/l440gx.c
@@ -27,17 +27,21 @@ static struct mtd_info *mymtd;
 
 
 /* Is this really the vpp port? */
+static DEFINE_SPINLOCK(l440gx_vpp_lock);
+static int l440gx_vpp_refcnt;
 static void l440gx_set_vpp(struct map_info *map, int vpp)
 {
-	unsigned long l;
+	unsigned long flags;
 
-	l = inl(VPP_PORT);
+	spin_lock_irqsave(&l440gx_vpp_lock, flags);
 	if (vpp) {
-		l |= 1;
+		if (++l440gx_vpp_refcnt == 1)   /* first nested 'on' */
+			outl(inl(VPP_PORT) | 1, VPP_PORT);
 	} else {
-		l &= ~1;
+		if (--l440gx_vpp_refcnt == 0)   /* last nested 'off' */
+			outl(inl(VPP_PORT) & ~1, VPP_PORT);
 	}
-	outl(l, VPP_PORT);
+	spin_unlock_irqrestore(&l440gx_vpp_lock, flags);
 }
 
 static struct map_info l440gx_map = {