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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Chris Packham <chris.packham@alliedtelesis.co.nz>,
        Brian Norris <computersforpeace@gmail.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 058/293] mtd: handle partitioning on devices
 with 0 erasesize
Thread-Topic: [PATCH AUTOSEL for 4.9 058/293] mtd: handle partitioning on
 devices with 0 erasesize
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Date:   Mon, 9 Apr 2018 00:23:36 +0000
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From: Chris Packham <chris.packham@alliedtelesis.co.nz>

[ Upstream commit 1eeef2d7483a7e3f8d2dd2a5b9939b3b814dc549 ]

erasesize is meaningful for flash devices but for SRAM there is no
concept of an erase block so erasesize is set to 0. When partitioning
these devices instead of ensuring partitions fall on erasesize
boundaries we ensure they fall on writesize boundaries.

Helped-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/mtd/mtdpart.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index fccdd49bb964..4bb63503aabf 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -385,8 +385,12 @@ static struct mtd_part *allocate_partition(struct mtd_=
info *master,
 			const struct mtd_partition *part, int partno,
 			uint64_t cur_offset)
 {
+	int wr_alignment =3D (master->flags & MTD_NO_ERASE) ? master->writesize:
+							    master->erasesize;
 	struct mtd_part *slave;
+	u32 remainder;
 	char *name;
+	u64 tmp;
=20
 	/* allocate the partition structure */
 	slave =3D kzalloc(sizeof(*slave), GFP_KERNEL);
@@ -488,10 +492,11 @@ static struct mtd_part *allocate_partition(struct mtd=
_info *master,
 	if (slave->offset =3D=3D MTDPART_OFS_APPEND)
 		slave->offset =3D cur_offset;
 	if (slave->offset =3D=3D MTDPART_OFS_NXTBLK) {
+		tmp =3D cur_offset;
 		slave->offset =3D cur_offset;
-		if (mtd_mod_by_eb(cur_offset, master) !=3D 0) {
-			/* Round up to next erasesize */
-			slave->offset =3D (mtd_div_by_eb(cur_offset, master) + 1) * master->era=
sesize;
+		remainder =3D do_div(tmp, wr_alignment);
+		if (remainder) {
+			slave->offset +=3D wr_alignment - remainder;
 			printk(KERN_NOTICE "Moving partition %d: "
 			       "0x%012llx -> 0x%012llx\n", partno,
 			       (unsigned long long)cur_offset, (unsigned long long)slave->offse=
t);
@@ -556,19 +561,22 @@ static struct mtd_part *allocate_partition(struct mtd=
_info *master,
 		slave->mtd.erasesize =3D master->erasesize;
 	}
=20
-	if ((slave->mtd.flags & MTD_WRITEABLE) &&
-	    mtd_mod_by_eb(slave->offset, &slave->mtd)) {
+	tmp =3D slave->offset;
+	remainder =3D do_div(tmp, wr_alignment);
+	if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 		/* Doesn't start on a boundary of major erase size */
 		/* FIXME: Let it be writable if it is on a boundary of
 		 * _minor_ erase size though */
 		slave->mtd.flags &=3D ~MTD_WRITEABLE;
-		printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase bloc=
k boundary -- force read-only\n",
+		printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/writ=
e block boundary -- force read-only\n",
 			part->name);
 	}
-	if ((slave->mtd.flags & MTD_WRITEABLE) &&
-	    mtd_mod_by_eb(slave->mtd.size, &slave->mtd)) {
+
+	tmp =3D slave->mtd.size;
+	remainder =3D do_div(tmp, wr_alignment);
+	if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 		slave->mtd.flags &=3D ~MTD_WRITEABLE;
-		printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase block =
-- force read-only\n",
+		printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write =
block -- force read-only\n",
 			part->name);
 	}
=20
--=20
2.15.1