mtd: devices: elm: check for device's presence before configuration

In case the driver is not probed - due to config mismatches or errors
in the DTS files - dev_get_drvdata() returns NULL, leading to an Ooops
during boot.

Make elm_config() return an error in such cases to propagate the error
up to the user, so it can fall back to software mode.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

2 files changed, 11 insertions, 3 deletions

diff --git a/drivers/mtd/devices/elm.c b/drivers/mtd/devices/elm.c
index 2ec5da9ee248..dccef9fdc1f2 100644
--- a/drivers/mtd/devices/elm.c
+++ b/drivers/mtd/devices/elm.c
@@ -81,14 +81,21 @@ static u32 elm_read_reg(struct elm_info *info, int offset)
  * @dev:        ELM device
  * @bch_type:   Type of BCH ecc
  */
-void elm_config(struct device *dev, enum bch_ecc bch_type)
+int elm_config(struct device *dev, enum bch_ecc bch_type)
 {
         u32 reg_val;
         struct elm_info *info = dev_get_drvdata(dev);
 
+        if (!info) {
+                dev_err(dev, "Unable to configure elm - device not probed?\n");
+                return -ENODEV;
+        }
+
         reg_val = (bch_type & ECC_BCH_LEVEL_MASK) | (ELM_ECC_SIZE << 16);
         elm_write_reg(info, ELM_LOCATION_CONFIG, reg_val);
         info->bch_type = bch_type;
+
+        return 0;
 }
 EXPORT_SYMBOL(elm_config);
 
diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 8e820ddf4e08..b97ef3b68ec6 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1701,8 +1701,9 @@ static int omap3_init_bch(struct mtd_info *mtd, int ecc_opt)
                 elm_node = of_find_node_by_phandle(be32_to_cpup(parp));
                 pdev = of_find_device_by_node(elm_node);
                 info->elm_dev = &pdev->dev;
-                elm_config(info->elm_dev, bch_type);
-                info->is_elm_used = true;
+
+                if (elm_config(info->elm_dev, bch_type) == 0)
+                        info->is_elm_used = true;
         }
 
         if (info->is_elm_used && (mtd->writesize <= 4096)) {