mtd: rawnand: protect access to rawnand devices while in suspend

Prevent rawnand access while in a suspended state.

Commit 013e6292 ("mtd: rawnand: Simplify the locking") allows the
rawnand layer to return errors rather than waiting in a blocking wait.

Tested on a iMX6ULL.

Fixes: 013e6292 ("mtd: rawnand: Simplify the locking")
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220208085213.1838273-1-sean@geanix.com

drivers/mtd/nand/raw/nand_base.c

@@ -338,16 +338,19 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
  *
  * Return: -EBUSY if the chip has been suspended, 0 otherwise
  */
-static int nand_get_device(struct nand_chip *chip)
+static void nand_get_device(struct nand_chip *chip)
 {
+	/* Wait until the device is resumed. */
+	while (1) {
 		mutex_lock(&chip->lock);
-	if (chip->suspended) {
-		mutex_unlock(&chip->lock);
-		return -EBUSY;
-	}
+		if (!chip->suspended) {
 			mutex_lock(&chip->controller->lock);
+			return;
+		}
+		mutex_unlock(&chip->lock);
 
-	return 0;
+		wait_event(chip->resume_wq, !chip->suspended);
+	}
 }
 
 /**
@@ -576,9 +579,7 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
 		nand_erase_nand(chip, &einfo, 0);
 
 		/* Write bad block marker to OOB */
-		ret = nand_get_device(chip);
-		if (ret)
-			return ret;
+		nand_get_device(chip);
 
 		ret = nand_markbad_bbm(chip, ofs);
 		nand_release_device(chip);
@@ -3826,9 +3827,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 	    ops->mode != MTD_OPS_RAW)
 		return -ENOTSUPP;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	if (!ops->datbuf)
 		ret = nand_do_read_oob(chip, from, ops);
@@ -4415,13 +4414,11 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
 			  struct mtd_oob_ops *ops)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
-	int ret;
+	int ret = 0;
 
 	ops->retlen = 0;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	switch (ops->mode) {
 	case MTD_OPS_PLACE_OOB:
@@ -4481,9 +4478,7 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
 		return -EIO;
 
 	/* Grab the lock and see if the device is available */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	/* Shift to get first page */
 	page = (int)(instr->addr >> chip->page_shift);
@@ -4570,7 +4565,7 @@ static void nand_sync(struct mtd_info *mtd)
 	pr_debug("%s: called\n", __func__);
 
 	/* Grab the lock and see if the device is available */
-	WARN_ON(nand_get_device(chip));
+	nand_get_device(chip);
 	/* Release it and go back */
 	nand_release_device(chip);
 }
@@ -4587,9 +4582,7 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
 	int ret;
 
 	/* Select the NAND device */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	nand_select_target(chip, chipnr);
 
@@ -4660,6 +4653,8 @@ static void nand_resume(struct mtd_info *mtd)
 			__func__);
 	}
 	mutex_unlock(&chip->lock);
+
+	wake_up_all(&chip->resume_wq);
 }
 
 /**
@@ -5438,6 +5433,7 @@ static int nand_scan_ident(struct nand_chip *chip, unsigned int maxchips,
 	chip->cur_cs = -1;
 
 	mutex_init(&chip->lock);
+	init_waitqueue_head(&chip->resume_wq);
 
 	/* Enforce the right timings for reset/detection */
 	chip->current_interface_config = nand_get_reset_interface_config();

include/linux/mtd/rawnand.h

@@ -1240,6 +1240,7 @@ struct nand_secure_region {
  * @lock: Lock protecting the suspended field. Also used to serialize accesses
  *        to the NAND device
  * @suspended: Set to 1 when the device is suspended, 0 when it's not
+ * @resume_wq: wait queue to sleep if rawnand is in suspended state.
  * @cur_cs: Currently selected target. -1 means no target selected, otherwise we
  *          should always have cur_cs >= 0 && cur_cs < nanddev_ntargets().
  *          NAND Controller drivers should not modify this value, but they're
@@ -1294,6 +1295,7 @@ struct nand_chip {
 	/* Internals */
 	struct mutex lock;
 	unsigned int suspended : 1;
+	wait_queue_head_t resume_wq;
 	int cur_cs;
 	int read_retries;
 	struct nand_secure_region *secure_regions;