linux-kernel - [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

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Message-Id: <20211026055551.3053598-2-sean@geanix.com>
Date:   Tue, 26 Oct 2021 07:55:48 +0200
From:   Sean Nyekjaer <sean@...nix.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     Sean Nyekjaer <sean@...nix.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

From: Boris Brezillon <boris.brezillon@...labora.com>

The BBT scan logic use the MTD helpers before the MTD layer had a
chance to initialize the device, and that leads to issues when
accessing the uninitialized suspend lock. Let's temporarily set the
suspend/resume hooks to NULL to skip the lock acquire/release step.

Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Tested-by: Sean Nyekjaer <sean@...nix.com>
Signed-off-by: Boris Brezillon <boris.brezillon@...labora.com>
Signed-off-by: Sean Nyekjaer <sean@...nix.com>
---
 drivers/mtd/nand/raw/nand_bbt.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
index b7ad030225f8..93d385703469 100644
--- a/drivers/mtd/nand/raw/nand_bbt.c
+++ b/drivers/mtd/nand/raw/nand_bbt.c
@@ -1397,8 +1397,28 @@ static int nand_create_badblock_pattern(struct nand_chip *this)
  */
 int nand_create_bbt(struct nand_chip *this)
 {
+	struct mtd_info *mtd = nand_to_mtd(this);
+	int (*suspend) (struct mtd_info *) = mtd->_suspend;
+	void (*resume) (struct mtd_info *) = mtd->_resume;
 	int ret;
 
+	/*
+	 * The BBT scan logic use the MTD helpers before the MTD layer had a
+	 * chance to initialize the device, and that leads to issues when
+	 * accessing the uninitialized suspend lock. Let's temporarily set the
+	 * suspend/resume hooks to NULL to skip the lock acquire/release step.
+	 *
+	 * FIXME: This is an ugly hack, so please don't copy this pattern to
+	 * other MTD implementations. The proper fix would be to implement a
+	 * generic BBT scan logic at the NAND level that's not using any of the
+	 * MTD helpers to access pages. We also might consider doing a two
+	 * step initialization at the MTD level (mtd_device_init() +
+	 * mtd_device_register()) so some of the fields are initialized
+	 * early.
+	 */
+	mtd->_suspend = NULL;
+	mtd->_resume = NULL;
+
 	/* Is a flash based bad block table requested? */
 	if (this->bbt_options & NAND_BBT_USE_FLASH) {
 		/* Use the default pattern descriptors */
@@ -1422,7 +1442,13 @@ int nand_create_bbt(struct nand_chip *this)
 			return ret;
 	}
 
-	return nand_scan_bbt(this, this->badblock_pattern);
+	ret = nand_scan_bbt(this, this->badblock_pattern);
+
+	/* Restore the suspend/resume hooks. */
+	mtd->_suspend = suspend;
+	mtd->_resume = resume;
+
+	return ret;
 }
 EXPORT_SYMBOL(nand_create_bbt);
 
-- 
2.33.0