Re: [PATCH v6 1/2] mtd: spi-nor: Delay the initialization of bank_size

Tudor Ambarus
2023-04-03T19:47:20Z

On 4/3/23 16:31, Miquel Raynal wrote:
> Hi Tudor,
>

Hi!

> tudor.ambarus@linaro.org wrote on Mon, 3 Apr 2023 09:23:24 +0100:
>
>> On 3/31/23 20:46, Miquel Raynal wrote:
>>> Bank size is derived from the chip's size, which in
>>> spi_nor_init_default_params() can still be zero if the size is not
>>> hardcoded in a table (eg. sfdp parsing). We need to delay the
>>> initialization of this field in the "late" helpers.
>>>
>>> Based on the fact that RWW compatible devices will use the bank_size to
>>> derive in which bank an access is made, we absolutely want to avoid
>>> divisions by 0. Right now there is no such opportunity between
>>> spi_nor_init_default_params() and spi_nor_late_init_params() but it is
>>> probably safer to enforce a default value (assuming 1 bank) as early as
>>> possible, just in case some day code using this variable is moved
>>> earlier than expected.
>>>
>>> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
>>> ---
>>> I made the choice to keep a default value, to be honest this is not
>>> actually needed today, so feel free to drop the line if you don't like
>>> it, both choices seem reasonable to me.
>>> ---
>>> drivers/mtd/spi-nor/core.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>>> index 9e6a0730cdb8..f436395ca489 100644
>>> --- a/drivers/mtd/spi-nor/core.c
>>> +++ b/drivers/mtd/spi-nor/core.c
>>> @@ -2882,6 +2882,8 @@ static void spi_nor_late_init_params(struct spi_nor *nor)
>>> */
>>> if (nor->flags & SNOR_F_HAS_LOCK && !nor->params->locking_ops)
>>> spi_nor_init_default_locking_ops(nor);
>>> +
>>> + nor->params->bank_size = div64_u64(nor->params->size, nor->info->n_banks);
>>> }
>>>
>>> /**
>>> @@ -2948,7 +2950,7 @@ static void spi_nor_init_default_params(struct spi_nor *nor)
>>> /* Set SPI NOR sizes. */
>>> params->writesize = 1;
>>> params->size = (u64)info->sector_size * info->n_sectors;
>>> - params->bank_size = div64_u64(params->size, info->n_banks);
>>> + params->bank_size = params->size;
>>
>> I'll get rid of this line entirely as you overwrite it anyway in
>> late_init and it's not used in between.
>
> Yes, as said above, I'm fine with both approaches. Shall I resend or
> will you edit when applying?
>

I'll handle it.

ta