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SubjectRe: [PATCH v2 1/3] UBI: Do not zero out EC and VID on ECC-ed NOR flashes
Date
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
>
> For NOR flashes EC and VID are zeroed out before an erase is issued to
> make sure UBI does not mistakenly treat the PEB as used and associate it
> with an LEB.
>
> But on some flashes, like the Cypress Semper S28 SPI NOR flash family,
> multi-pass page programming is not allowed on the default ECC scheme.
> This means zeroing out these magic numbers will result in the flash
> throwing a page programming error.
>
> Do not zero out EC and VID for such flashes. A writesize > 1 is an
> indication of an ECC-ed flash.
>
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> ---
>
> Notes:
> Changes in v2:
>
> - Use mtd->writesize to check if multi-pass programming can be done
> instead of using MTD_NO_MULTI_PASS_WRITE.
> - Remove the assertion that a NOR flash most have writesize of 1.
>
> drivers/mtd/ubi/build.c | 4 +---
> drivers/mtd/ubi/io.c | 9 ++++++++-
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
> index e85b04e9716b..25fd7816b1f4 100644
> --- a/drivers/mtd/ubi/build.c
> +++ b/drivers/mtd/ubi/build.c
> @@ -628,10 +628,8 @@ static int io_init(struct ubi_device *ubi, int max_beb_per1024)
> ubi->bad_peb_limit = get_bad_peb_limit(ubi, max_beb_per1024);
> }
>
> - if (ubi->mtd->type == MTD_NORFLASH) {
> - ubi_assert(ubi->mtd->writesize == 1);
> + if (ubi->mtd->type == MTD_NORFLASH)
> ubi->nor_flash = 1;
> - }
>
> ubi->min_io_size = ubi->mtd->writesize;
> ubi->hdrs_min_io_size = ubi->mtd->writesize >> ubi->mtd->subpage_sft;
> diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
> index 14d890b00d2c..2f3312c31e51 100644
> --- a/drivers/mtd/ubi/io.c
> +++ b/drivers/mtd/ubi/io.c
> @@ -535,7 +535,14 @@ int ubi_io_sync_erase(struct ubi_device *ubi, int pnum, int torture)
> return -EROFS;
> }
>
> - if (ubi->nor_flash) {
> + /*
> + * If the flash is ECC-ed then we have to erase the ECC block before we
> + * can write to it. But the write is in preparation to an erase in the
> + * first place. This means we cannot zero out EC and VID before the
> + * erase and we just have to hope the flash starts erasing from the
> + * start of the page.
> + */
> + if (ubi->nor_flash && ubi->mtd->writesize == 1) {

Are there any SPI NORs with ECC block size of 4 bytes? Should we call
nor_erase_prepare() in this case?

Anyway, there's none in SPI NOR as of now, so:

Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>

> err = nor_erase_prepare(ubi, pnum);
> if (err)
> return err;
> --
> 2.28.0
>

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