linux-kernel - Re: [PATCH v5 1/3] mtd: spi-nor: atmel: remove global protection flag

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Message-ID: <7b5159c1-5457-b43c-2bf2-1a17ed6df34a@microchip.com>
Date:   Tue, 24 Nov 2020 19:09:09 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>,
        <boris.brezillon@...labora.com>
Subject: Re: [PATCH v5 1/3] mtd: spi-nor: atmel: remove global protection flag

On 10/3/20 6:32 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> This is considered bad for the following reasons:
>  (1) We only support the block protection with BPn bits for write
>      protection. Not all Atmel parts support this.
>  (2) Newly added flash chip will automatically inherit the "has
>      locking" support and thus needs to explicitly tested. Better
>      be opt-in instead of opt-out.
>  (3) There are already supported flashes which doesn't support
>      the locking scheme. So I assume this wasn't properly tested
>      before adding that chip; which enforces my previous argument
>      that locking support should be an opt-in.
> 
> Remove the global flag and add individual flags to all flashes which
> supports BP locking. In particular the following flashes don't support
> the BP scheme:
>  - AT26F004
>  - AT25SL321
>  - AT45DB081D
> 
> Please note, that some flashes which are marked as SPI_NOR_HAS_LOCK just
> support Global Protection, i.e. not our supported block protection
> locking scheme. This is to keep backwards compatibility with the
> current "unlock all at boot" mechanism. In particular the following
> flashes doesn't have BP bits:
>  - AT25DF041A
>  - AT25DF321
>  - AT25DF321A
>  - AT25DF641
>  - AT26DF081A
>  - AT26DF161A
>  - AT26DF321
> 
> Signed-off-by: Michael Walle <michael@...le.cc>

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

> ---
> changes since v4:
>  - none
> 
> changes since v3/v2/v1:
>  - there was no such version because this patch was bundled with another
>    patch
> 
> changes since RFC:
>  - mention the flashes which just support the "Global Unprotect" in the
>    commit message
> 
>  drivers/mtd/spi-nor/atmel.c | 28 +++++++++-------------------
>  1 file changed, 9 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/atmel.c b/drivers/mtd/spi-nor/atmel.c
> index 3f5f21a473a6..49d392c6c8bc 100644
> --- a/drivers/mtd/spi-nor/atmel.c
> +++ b/drivers/mtd/spi-nor/atmel.c
> @@ -10,37 +10,27 @@
> 
>  static const struct flash_info atmel_parts[] = {
>         /* Atmel -- some are (confusingly) marketed as "DataFlash" */
> -       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K) },
> -       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K) },
> +       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/587164/ATMELCorporation/AT25FS010/1
BP bits are at bit 2, 3, 5 and 6.
BP0, BP1, BP3, BP4 and WPEN, are nonvolatile cells

> +       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/587165/ATMELCorporation/AT25FS040/1
BP bits are at bit 2, 3, 4, 5, and 6.
BP0, BP1, BP2, BP3, BP4 are nonvolatile cells

> 
> -       { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K) },
> -       { "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K) },
> -       { "at25df321a", INFO(0x1f4701, 0, 64 * 1024,  64, SECT_4K) },
> -       { "at25df641",  INFO(0x1f4800, 0, 64 * 1024, 128, SECT_4K) },
> +       { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/975331/Adesto/AT25DF041A/1
Global Protect/Unprotect using Write SR command:
Global Unlock: write 0x00 to SR
Global Lock: Read SR. If SR.SPRL is 1 write 0xff to SR, else write 0x7f.

Upon device power-up or after a device reset, each Sector Protection
Register will default to the logical “1” state indicating that all
sectors are protected and cannot be programmed or erased.


> +       { "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/609207/ATMELCorporation/AT25DF321/1
Global Protect/Unprotect same as in at25df041a.

> +       { "at25df321a", INFO(0x1f4701, 0, 64 * 1024,  64, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/829669/Adesto/AT25DF321A/1
Global Protect/Unprotect same as in at25df041a.

> +       { "at25df641",  INFO(0x1f4800, 0, 64 * 1024, 128, SECT_4K | SPI_NOR_HAS_LOCK) },

https://www.adestotech.com/wp-content/uploads/doc3680.pdf
Global Protect/Unprotect same as in at25df041a.

> 
>         { "at25sl321",  INFO(0x1f4216, 0, 64 * 1024, 64,
>                              SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },

https://www.adestotech.com/wp-content/uploads/AT25SL321_112.pdf
Ok, just hw write protection.

> 
>         { "at26f004",   INFO(0x1f0400, 0, 64 * 1024,  8, SECT_4K) },

https://cdn.sos.sk/productdata/08/5e/c7c8063e/at-26-f004-ssu.pdf
OK, never worked, just Individual Sector Protection for Program/Erase Protection

> -       { "at26df081a", INFO(0x1f4501, 0, 64 * 1024, 16, SECT_4K) },
> -       { "at26df161a", INFO(0x1f4601, 0, 64 * 1024, 32, SECT_4K) },
> -       { "at26df321",  INFO(0x1f4700, 0, 64 * 1024, 64, SECT_4K) },
> +       { "at26df081a", INFO(0x1f4501, 0, 64 * 1024, 16, SECT_4K | SPI_NOR_HAS_LOCK) },

https://www.adestotech.com/wp-content/uploads/doc3600.pdf
Global Protect/Unprotect same as in at25df041a.

> +       { "at26df161a", INFO(0x1f4601, 0, 64 * 1024, 32, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/562306/ATMELCorporation/AT26DF161/1
Global Protect/Unprotect same as in at25df041a.

> +       { "at26df321",  INFO(0x1f4700, 0, 64 * 1024, 64, SECT_4K | SPI_NOR_HAS_LOCK) },

https://datasheetspdf.com/pdf-file/609208/ATMELCorporation/AT26DF321/1
Global Protect/Unprotect same as in at25df041a.

> 
>         { "at45db081d", INFO(0x1f2500, 0, 64 * 1024, 16, SECT_4K) },

https://datasheetspdf.com/pdf-file/856198/Adesto/AT45DB081D/1
OK. Individual sector protection.

>  };
> 
> -static void atmel_default_init(struct spi_nor *nor)
> -{
> -       nor->flags |= SNOR_F_HAS_LOCK;
> -}
> -
> -static const struct spi_nor_fixups atmel_fixups = {
> -       .default_init = atmel_default_init,
> -};
> -
>  const struct spi_nor_manufacturer spi_nor_atmel = {
>         .name = "atmel",
>         .parts = atmel_parts,
>         .nparts = ARRAY_SIZE(atmel_parts),
> -       .fixups = &atmel_fixups,
>  };
> --
> 2.20.1
>