mtd: spi-nor: core: Allow flashes to specify MTD writesize

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@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201201102711.8727-3-p.yadav@ti.com

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 7b4850f9422339b0e715e9bcff33e13a7015c47a..ae991ff458a093a1d0d735589e82452d7f7e9510 100644 (file)
--- 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;
 
@@ -3430,7 +3431,7 @@ 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 0a775a7b5606139d8da7365d66645413677cde35..5ab3f269a23cc853cdcc3ae78175cf38946e4040 100644 (file)
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -193,6 +193,8 @@ struct spi_nor_locking_ops {
  * Serial Flash Discoverable Parameters (SFDP) tables.
  *
  * @size:              the flash memory density in bytes.
+ * @writesize          Minimal writable flash unit size. Defaults to 1. Set to
+ *                     ECC unit size for ECC-ed flashes.
  * @page_size:         the page size of the SPI NOR flash memory.
  * @rdsr_dummy:                dummy cycles needed for Read Status Register command.
  * @rdsr_addr_nbytes:  dummy address bytes needed for Read Status Register
@@ -219,6 +221,7 @@ struct spi_nor_locking_ops {
  */
 struct spi_nor_flash_parameter {
        u64                             size;
+       u32                             writesize;
        u32                             page_size;
        u8                              rdsr_dummy;
        u8                              rdsr_addr_nbytes;