mtd: fix MTD suspend

Commits 3fe4bae88460869a8e553397cd9057a4ee7ca341 and
079c985e7a6f4ce60f931cebfdd5ee3c3 broke MTD suspend in 2 ways:

1. When the '->suspend' method is not present, we return -EOPNOTSUPP, but
   the callers of 'mtd_suspend()' expects 0 instead.
2. Checking of the 'mtd' parameter against NULL has been incorrectly removed
   in 'mtd_cls_suspend()'.

This patch fixes the breakages. This has been found, analyzed, reported
and tested by Rafael J. Wysocki <rjw@sisk.pl>.

Note, this patch is not needed in the stable tree because it causes a
regression introduced during the v3.3 merge window.

Reported-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

2 files changed, 2 insertions, 4 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 6ae9ca01388b..9a9ce71a71fc 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -119,7 +119,7 @@ static int mtd_cls_suspend(struct device *dev, pm_message_t state)
 {
         struct mtd_info *mtd = dev_get_drvdata(dev);
 
-        return mtd_suspend(mtd);
+        return mtd ? mtd_suspend(mtd) : 0;
 }
 
 static int mtd_cls_resume(struct device *dev)
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 1a81fde8f333..d8c7aad7331c 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -427,9 +427,7 @@ static inline int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 
 static inline int mtd_suspend(struct mtd_info *mtd)
 {
-        if (!mtd->suspend)
-                return -EOPNOTSUPP;
-        return mtd->suspend(mtd);
+        return mtd->suspend ? mtd->suspend(mtd) : 0;
 }
 
 static inline void mtd_resume(struct mtd_info *mtd)