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: NDaniel Mack <zonque@gmail.com>
Acked-by: NPeter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

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);
 

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)) {

include/linux/platform_data/elm.h

@@ -50,5 +50,5 @@ struct elm_errorvec {
 
 void elm_decode_bch_error_page(struct device *dev, u8 *ecc_calc,
 		struct elm_errorvec *err_vec);
-void elm_config(struct device *dev, enum bch_ecc bch_type);
+int elm_config(struct device *dev, enum bch_ecc bch_type);
 #endif /* __ELM_H */