linux-kernel - Re: [PATCH v6 4/5] mtd: spi-nor: atmel: Fix unlock

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Message-ID: <ba9850c1-a684-6376-7331-2e09567dcb73@microchip.com>
Date:   Sat, 28 Nov 2020 08:25:09 +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 v6 4/5] mtd: spi-nor: atmel: Fix unlock_all() for
 AT25FS010/040

On 11/26/20 10:26 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> These flashes have some weird BP bits mapping which aren't supported in
> the current locking code. Just add a simple unlock op to unprotect the
> entire flash array which is needed for legacy behavior.
> 
> Signed-off-by: Michael Walle <michael@...le.cc>
> ---
> changes since v5
>  - new patch
> 
>  drivers/mtd/spi-nor/atmel.c | 53 +++++++++++++++++++++++++++++++++++--
>  drivers/mtd/spi-nor/core.c  |  2 +-
>  drivers/mtd/spi-nor/core.h  |  1 +
>  3 files changed, 53 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/atmel.c b/drivers/mtd/spi-nor/atmel.c
> index 49d392c6c8bc..fe6a4653823d 100644
> --- a/drivers/mtd/spi-nor/atmel.c
> +++ b/drivers/mtd/spi-nor/atmel.c
> @@ -8,10 +8,59 @@
> 
>  #include "core.h"
> 
> +/*
> + * The Atmel AT25FS010/AT25FS040 parts have some weird configuration for the
> + * block protection bits. We don't support them. But legacy behaviour in linux
> + * is to unlock the whole flash array on startup. Therefore, we have to support
> + * exactly this operation.
> + */
> +static int atmel_at25fs_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
> +{
> +       return -EOPNOTSUPP;
> +}
> +
> +static int atmel_at25fs_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
> +{
> +       /* We only support unlocking the whole flash array */
> +       if (ofs || len != nor->params->size)
> +               return -EINVAL;
> +
> +       /*
> +        * Write 0x00 to the status register to try to disable the write
> +        * protection. This will fail if SRWD (the datasheet calls it WPEN) is
> +        * set. But there is nothing we can do.
> +        */

can't we do the same as you did in 5/5?
+       ret = spi_nor_read_sr(nor, nor->bouncebuf);
+       if (ret)
+               return ret;
+
+       sr = nor->bouncebuf[0];
+
+       if (sr & SR_SRWD) {
+               sr &= ~SR_SRWD;
+               ret = spi_nor_write_sr_and_check(nor, sr);
+               if (ret)
+                       return ret;
+       }

If SRWD is set to 1, we first try to set it to 0. If WP# is asserted, we
will catch this in spi_nor_write_sr_and_check()

> +       nor->bouncebuf[0] = 0;
> +
> +       return spi_nor_write_sr(nor, nor->bouncebuf, 1);

and then you can use spi_nor_write_sr_and_check here

> +}
> +
> +static int atmel_at25fs_is_locked(struct spi_nor *nor, loff_t ofs, uint64_t len)
> +{
> +       return -EOPNOTSUPP;
> +}
> +
> +static const struct spi_nor_locking_ops atmel_at25fs_locking_ops = {
> +       .lock = atmel_at25fs_lock,
> +       .unlock = atmel_at25fs_unlock,
> +       .is_locked = atmel_at25fs_is_locked,
> +};
> +
> +static void atmel_at25fs_default_init(struct spi_nor *nor)
> +{
> +       nor->params->locking_ops = &atmel_at25fs_locking_ops;
> +}
> +
> +static const struct spi_nor_fixups atmel_at25fs_fixups = {
> +       .default_init = atmel_at25fs_default_init,
> +};
> +
>  static const struct flash_info atmel_parts[] = {
>         /* Atmel -- some are (confusingly) marketed as "DataFlash" */
> -       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K | SPI_NOR_HAS_LOCK) },
> -       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },
> +       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K | SPI_NOR_HAS_LOCK)
> +               .fixups = &atmel_at25fs_fixups },
> +       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK)
> +               .fixups = &atmel_at25fs_fixups },
> 
>         { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },
>         { "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K | SPI_NOR_HAS_LOCK) },
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 5bee7c8da4dc..8c06a28a90de 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -861,7 +861,7 @@ int spi_nor_wait_till_ready(struct spi_nor *nor)
>   *
>   * Return: 0 on success, -errno otherwise.
>   */
> -static int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len)
> +int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len)
>  {
>         int ret;
> 
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index 0a775a7b5606..16b350e1d865 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -430,6 +430,7 @@ void spi_nor_unlock_and_unprep(struct spi_nor *nor);
>  int spi_nor_sr1_bit6_quad_enable(struct spi_nor *nor);
>  int spi_nor_sr2_bit1_quad_enable(struct spi_nor *nor);
>  int spi_nor_sr2_bit7_quad_enable(struct spi_nor *nor);
> +int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len);
> 
>  int spi_nor_xread_sr(struct spi_nor *nor, u8 *sr);
>  ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
> --
> 2.20.1
>