Re: [PATCH v2 2/3] mtd: spi-nor: core: Allow flashes to specify MTD writesize

From: Pratyush Yadav
Date: Mon Nov 30 2020 - 08:15:55 EST


On 28/11/20 10:59AM, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> On 11/18/20 8:24 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > Some flashes like the Cypress S28 family use ECC. Under this ECC scheme,
> > multi-pass writes to an ECC block is not allowed. In other words, once
> > data is programmed to an ECC block, it can't be programmed again without
> > erasing it first.
> >
> > Upper layers like file systems need to be given this information so they
> > do not cause error conditions on the flash by attempting multi-pass
> > programming. This can be done by setting 'writesize' in 'struct
> > mtd_info'.
> >
> > Set the default to 1 but allow flashes to modify it in fixup hooks. If
> > more flashes show up with this constraint in the future it might be
> > worth it to add it to 'struct flash_info', but for now increasing its
> > size is not worth it.
> >
> > Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx>
> > ---
> >
> > Notes:
> > New in v2.
> >
> > drivers/mtd/spi-nor/core.c | 4 +++-
> > drivers/mtd/spi-nor/core.h | 3 +++
> > 2 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index 5bee7c8da4dc..80fbcb9c0828 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
> > @@ -3054,6 +3054,8 @@ static int spi_nor_init_params(struct spi_nor *nor)
> > if (!nor->params)
> > return -ENOMEM;
> >
> > + nor->params->writesize = 1;
> > +
>
> please do default inits in spi_nor_info_init_params(). A good place would be:
>
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2885,6 +2885,7 @@ static void spi_nor_info_init_params(struct spi_nor *nor)
> nor->flags |= SNOR_F_HAS_16BIT_SR;
>
> /* Set SPI NOR sizes. */
> + params->writesize = 1;
> params->size = (u64)info->sector_size * info->n_sectors;
> params->page_size = info->page_size;

Ok.

>
> > spi_nor_info_init_params(nor);
> >
> > spi_nor_manufacturer_init_params(nor);
> > @@ -3430,7 +3432,7 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
> > mtd->name = dev_name(dev);
> > mtd->priv = nor;
> > mtd->type = MTD_NORFLASH;
> > - mtd->writesize = 1;
> > + mtd->writesize = nor->params->writesize;
> > mtd->flags = MTD_CAP_NORFLASH;
> > mtd->size = nor->params->size;
> > mtd->_erase = spi_nor_erase;
> > diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> > index 0a775a7b5606..413ea311e632 100644
> > --- a/drivers/mtd/spi-nor/core.h
> > +++ b/drivers/mtd/spi-nor/core.h
> > @@ -197,6 +197,8 @@ struct spi_nor_locking_ops {
> > * @rdsr_dummy: dummy cycles needed for Read Status Register command.
> > * @rdsr_addr_nbytes: dummy address bytes needed for Read Status Register
> > * command.
> > + * @writesize Minimal writable flash unit size. Defaults to 1. Set to
> > + * ECC unit size for ECC-ed flashes.
> > * @hwcaps: describes the read and page program hardware
> > * capabilities.
> > * @reads: read capabilities ordered by priority: the higher index
> > @@ -222,6 +224,7 @@ struct spi_nor_flash_parameter {
> > u32 page_size;
>
> I would put writesize before or after page_size, because they are related.
> Also, it would probably avoid padding.

Ok.

> With these addressed, one can add:
>
> Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

Thanks.

> > u8 rdsr_dummy;
> > u8 rdsr_addr_nbytes;
> > + u32 writesize;
> >
> > struct spi_nor_hwcaps hwcaps;
> > struct spi_nor_read_command reads[SNOR_CMD_READ_MAX];
> > --
> > 2.28.0
> >
>

--
Regards,
Pratyush Yadav
Texas Instruments India