From: Chris Packham <chris.pack...@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.brezil...@free-electrons.com>
Signed-off-by: Chris Packham <chris.pack...@alliedtelesis.co.nz>
Acked-by: Boris Brezillon <boris.brezil...@free-electrons.com>
Signed-off-by: Brian Norris <computersforpe...@gmail.com>
Signed-off-by: Sasha Levin <alexander.le...@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 f8ba153f63bf..3b7ac1989f90 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -353,8 +353,12 @@ static struct mtd_part *allocate_partition(struct mtd_info 
*master,
                        const struct mtd_partition *part, int partno,
                        uint64_t cur_offset)
 {
+       int wr_alignment = (master->flags & MTD_NO_ERASE) ? master->writesize:
+                                                           master->erasesize;
        struct mtd_part *slave;
+       u32 remainder;
        char *name;
+       u64 tmp;
 
        /* allocate the partition structure */
        slave = kzalloc(sizeof(*slave), GFP_KERNEL);
@@ -449,10 +453,11 @@ static struct mtd_part *allocate_partition(struct 
mtd_info *master,
        if (slave->offset == MTDPART_OFS_APPEND)
                slave->offset = cur_offset;
        if (slave->offset == MTDPART_OFS_NXTBLK) {
+               tmp = cur_offset;
                slave->offset = cur_offset;
-               if (mtd_mod_by_eb(cur_offset, master) != 0) {
-                       /* Round up to next erasesize */
-                       slave->offset = (mtd_div_by_eb(cur_offset, master) + 1) 
* master->erasesize;
+               remainder = do_div(tmp, wr_alignment);
+               if (remainder) {
+                       slave->offset += wr_alignment - remainder;
                        printk(KERN_NOTICE "Moving partition %d: "
                               "0x%012llx -> 0x%012llx\n", partno,
                               (unsigned long long)cur_offset, (unsigned long 
long)slave->offset);
@@ -517,19 +522,22 @@ static struct mtd_part *allocate_partition(struct 
mtd_info *master,
                slave->mtd.erasesize = master->erasesize;
        }
 
-       if ((slave->mtd.flags & MTD_WRITEABLE) &&
-           mtd_mod_by_eb(slave->offset, &slave->mtd)) {
+       tmp = slave->offset;
+       remainder = 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 &= ~MTD_WRITEABLE;
-               printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an 
erase block boundary -- force read-only\n",
+               printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an 
erase/write block boundary -- force read-only\n",
                        part->name);
        }
-       if ((slave->mtd.flags & MTD_WRITEABLE) &&
-           mtd_mod_by_eb(slave->mtd.size, &slave->mtd)) {
+
+       tmp = slave->mtd.size;
+       remainder = do_div(tmp, wr_alignment);
+       if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
                slave->mtd.flags &= ~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);
        }
 
-- 
2.15.1

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