linux-kernel - Re: [PATCH v3 2/2] mtd: spi-nor: Avoid setting SRWD bit in SR if WP# signal not connected

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Message-ID: <6190c9c4-6d6e-7577-f2a4-8fbede61b405@linaro.org>
Date:   Fri, 30 Jun 2023 09:48:23 +0100
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     Michael Walle <michael@...le.cc>,
        Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
Cc:     pratyush@...nel.org, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        git@....com, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        amitrkcian2002@...il.com
Subject: Re: [PATCH v3 2/2] mtd: spi-nor: Avoid setting SRWD bit in SR if WP#
 signal not connected



On 6/27/23 07:14, Michael Walle wrote:
> Am 2023-06-25 12:02, schrieb Amit Kumar Mahapatra:
>> Setting the status register write disable (SRWD) bit in the status
>> register (SR) with WP# signal of the flash left floating or wrongly tied to
>> GND (that includes internal pull-downs), will configure the SR permanently
>> as read-only. If WP# signal is left floating or wrongly tied to GND, avoid
>> setting SRWD bit while writing the SR during flash protection.
>>
>> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
>> ---
>>  drivers/mtd/spi-nor/core.c | 3 +++
>>  drivers/mtd/spi-nor/core.h | 1 +
>>  drivers/mtd/spi-nor/swp.c  | 9 +++++++--
>>  3 files changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 0bb0ad14a2fc..520f5ab86d2b 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -2864,6 +2864,9 @@ static void spi_nor_init_flags(struct spi_nor *nor)
>>      if (flags & NO_CHIP_ERASE)
>>          nor->flags |= SNOR_F_NO_OP_CHIP_ERASE;
>>
>> +    if (of_property_read_bool(np, "no-wp"))
>> +        nor->flags |= SNOR_F_NO_WP;
>> +
> 
> Please put it below the of_property_read_bool() which is already
> there, just to keep things sorted.
> 
>>      if (flags & SPI_NOR_RWW && nor->info->n_banks > 1 &&
>>          !nor->controller_ops)
>>          nor->flags |= SNOR_F_RWW;
>> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
>> index 4fb5ff09c63a..55b5e7abce6e 100644
>> --- a/drivers/mtd/spi-nor/core.h
>> +++ b/drivers/mtd/spi-nor/core.h
>> @@ -132,6 +132,7 @@ enum spi_nor_option_flags {
>>      SNOR_F_SWP_IS_VOLATILE    = BIT(13),
>>      SNOR_F_RWW        = BIT(14),
>>      SNOR_F_ECC        = BIT(15),
>> +    SNOR_F_NO_WP        = BIT(16),
> 
> See the comment right above this enum :/
> 
>>  };
>>
>>  struct spi_nor_read_command {
>> diff --git a/drivers/mtd/spi-nor/swp.c b/drivers/mtd/spi-nor/swp.c
>> index 0ba716e84377..cfaba41d74d6 100644
>> --- a/drivers/mtd/spi-nor/swp.c
>> +++ b/drivers/mtd/spi-nor/swp.c
>> @@ -214,8 +214,13 @@ static int spi_nor_sr_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
>>
>>      status_new = (status_old & ~mask & ~tb_mask) | val;
>>
>> -    /* Disallow further writes if WP pin is asserted */
>> -    status_new |= SR_SRWD;
>> +    /*
>> +     * Disallow further writes if WP# pin is neither left floating nor
>> +     * wrongly tied to GND(that includes internal pull-downs).
> 
> nit: space missing
> 
> Otherwise looks good.
> 

Thanks, Michael.

Amit, would be good if you can address Michael's comments and
resubmit. If not, I'll amend the patch by myself when applying.

Cheers,
ta