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    SubjectRe: [PATCH 3/4] mtd: mchp23k256: add partitioning support
    Hi Chris,

    On Mon, 22 May 2017 04:52:34 +0000
    Chris Packham <Chris.Packham@alliedtelesis.co.nz> wrote:

    > On 18/05/17 03:29, Boris Brezillon wrote:
    > > Hi Chris,
    > >
    > > On Wed, 17 May 2017 17:39:07 +1200
    > > Chris Packham <chris.packham@alliedtelesis.co.nz> wrote:
    > >
    > >> Setting the of_node for the mtd device allows the generic mtd code to
    > >> setup the partitions. Additionally we must specify a non-zero erasesize
    > >> for the partitions to be writeable.
    > >>
    > >> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
    > >> ---
    > >> drivers/mtd/devices/mchp23k256.c | 5 +++++
    > >> 1 file changed, 5 insertions(+)
    > >>
    > >> diff --git a/drivers/mtd/devices/mchp23k256.c b/drivers/mtd/devices/mchp23k256.c
    > >> index 2542f5b8b63f..02c6b9dcbd3e 100644
    > >> --- a/drivers/mtd/devices/mchp23k256.c
    > >> +++ b/drivers/mtd/devices/mchp23k256.c
    > >> @@ -143,6 +143,7 @@ static int mchp23k256_probe(struct spi_device *spi)
    > >>
    > >> data = dev_get_platdata(&spi->dev);
    > >>
    > >> + mtd_set_of_node(&flash->mtd, spi->dev.of_node);
    > >> flash->mtd.dev.parent = &spi->dev;
    > >> flash->mtd.type = MTD_RAM;
    > >> flash->mtd.flags = MTD_CAP_RAM;
    > >> @@ -151,6 +152,10 @@ static int mchp23k256_probe(struct spi_device *spi)
    > >> flash->mtd._read = mchp23k256_read;
    > >> flash->mtd._write = mchp23k256_write;
    > >>
    > >> + flash->mtd.erasesize = PAGE_SIZE;
    > >> + while (flash->mtd.size & (flash->mtd.erasesize - 1))
    > >> + flash->mtd.erasesize >>= 1;
    > >> +
    > >
    > > Can we fix allocate_partition() to properly handle the
    > > master->erasesize == 0 case instead of doing that?
    > >
    >
    > Do you mean something like this?

    I had something slightly different in mind (see below).

    >
    > diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
    > index ea5e5307f667..0cd20ed6b374 100644
    > --- a/drivers/mtd/mtdpart.c
    > +++ b/drivers/mtd/mtdpart.c
    > @@ -577,6 +577,7 @@ static struct mtd_part *allocate_partition(struct
    > mtd_info *master,
    > part->name);
    > }
    > if ((slave->mtd.flags & MTD_WRITEABLE) &&
    > + master->erasesize != 0 &&
    > mtd_mod_by_eb(slave->mtd.size, &slave->mtd)) {
    > slave->mtd.flags &= ~MTD_WRITEABLE;
    >
    >
    > I'm happy to submit this as a formal patch but it could potentially
    > affect a number of devices. Whereas the snippet I initially added is
    > consistent with drivers/mtd/chips/map_ram.c.

    Well, if you're duplicating a workaround that's a good sign this should
    actually be handled in the core.

    >
    > For now I'll leave v2 as-is but I can send a v3 if needed.
    >

    --->8---
    diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
    index ea5e5307f667..378ff4a9174e 100644
    --- a/drivers/mtd/mtdpart.c
    +++ b/drivers/mtd/mtdpart.c
    @@ -393,7 +393,9 @@ 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->erasesize ? : master->writesize;
    struct mtd_part *slave;
    + u32 remainder;
    char *name;

    /* allocate the partition structure */
    @@ -499,10 +501,12 @@ 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) {
    + u64 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);
    @@ -567,19 +571,22 @@ 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);
    }

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