Re: [PATCH v15 4/8] mtd: spi-nor: Do not change nor->addr_nbytes at SFDP parsing time

[<Tudor.Ambarus@microchip.com>]

On 5/31/22 14:30, Pratyush Yadav wrote:
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> 
> On 10/05/22 07:10AM, tkuw584924@gmail.com wrote:
>> From: Tudor Ambarus <tudor.ambarus@microchip.com>
>>
>> At the SFDP parsing time we should not change members of struct spi_nor,
>> but instead fill members of struct spi_nor_flash_parameters which could
>> leter on be used by callers. The caller will then decide if SFDP params
> 
> s/leter/later/
> 
>> should be used and more importantly when they should be used. Clean the
>> code flow and don't initialize nor->addr_nbytes at SFDP parsing time.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
>> Tested-By: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
>> ---
>>  drivers/mtd/spi-nor/core.c |  5 ++---
>>  drivers/mtd/spi-nor/core.h |  2 ++
>>  drivers/mtd/spi-nor/sfdp.c | 18 ++++++------------
>>  3 files changed, 10 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 7db6b41d7c30..dd71deba9f11 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -2272,8 +2272,8 @@ static int spi_nor_default_setup(struct spi_nor *nor,
>>
>>  static int spi_nor_set_addr_nbytes(struct spi_nor *nor)
>>  {
>> -     if (nor->addr_nbytes) {
>> -             /* already configured from SFDP */
>> +     if (nor->params->addr_nbytes) {
>> +             nor->addr_nbytes = nor->params->addr_nbytes;
>>       } else if (nor->read_proto == SNOR_PROTO_8_8_8_DTR) {
>>               /*
>>                * In 8D-8D-8D mode, one byte takes half a cycle to transfer. So
>> @@ -2518,7 +2518,6 @@ static void spi_nor_sfdp_init_params_deprecated(struct spi_nor *nor)
>>
>>       if (spi_nor_parse_sfdp(nor)) {
>>               memcpy(nor->params, &sfdp_params, sizeof(*nor->params));
>> -             nor->addr_nbytes = 0;
>>               nor->flags &= ~SNOR_F_4B_OPCODES;
>>       }
>>  }
>> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
>> index fe7683fe1b4d..41df8bc8e008 100644
>> --- a/drivers/mtd/spi-nor/core.h
>> +++ b/drivers/mtd/spi-nor/core.h
>> @@ -345,6 +345,7 @@ struct spi_nor_otp {
>>   * @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.
>> + * @addr_nbytes:     number of address bytes to send.
>>   * @rdsr_dummy:              dummy cycles needed for Read Status Register command
>>   *                   in octal DTR mode.
>>   * @rdsr_addr_nbytes:        dummy address bytes needed for Read Status Register
>> @@ -377,6 +378,7 @@ struct spi_nor_flash_parameter {
>>       u64                             size;
>>       u32                             writesize;
>>       u32                             page_size;
>> +     u8                              addr_nbytes;
>>       u8                              rdsr_dummy;
>>       u8                              rdsr_addr_nbytes;
>>
>> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
>> index 058ce218d2af..90d7c25f7281 100644
>> --- a/drivers/mtd/spi-nor/sfdp.c
>> +++ b/drivers/mtd/spi-nor/sfdp.c
>> @@ -178,19 +178,16 @@ static int spi_nor_read_raw(struct spi_nor *nor, u32 addr, size_t len, u8 *buf)
>>  static int spi_nor_read_sfdp(struct spi_nor *nor, u32 addr,
>>                            size_t len, void *buf)
>>  {
>> -     u8 addr_nbytes;
>>       int ret;
>>
>> -     addr_nbytes = nor->addr_nbytes;
>> -
>>       nor->read_opcode = SPINOR_OP_RDSFDP;
>>       nor->addr_nbytes = 3;
>>       nor->read_dummy = 8;
>>
>>       ret = spi_nor_read_raw(nor, addr, len, buf);
>>
>> -     nor->addr_nbytes = addr_nbytes;
>>       /* Restore setup to its uninitialized state. */
>> +     nor->addr_nbytes = 0;
>>       nor->read_opcode = 0;
>>       nor->read_dummy = 0;
>>
>> @@ -461,11 +458,11 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>>       switch (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK) {
>>       case BFPT_DWORD1_ADDRESS_BYTES_3_ONLY:
>>       case BFPT_DWORD1_ADDRESS_BYTES_3_OR_4:
>> -             nor->addr_nbytes = 3;
>> +             params->addr_nbytes = 3;
>>               break;
>>
>>       case BFPT_DWORD1_ADDRESS_BYTES_4_ONLY:
>> -             nor->addr_nbytes = 4;
>> +             params->addr_nbytes = 4;
>>               break;
>>
>>       default:
>> @@ -652,7 +649,7 @@ static u8 spi_nor_smpt_addr_nbytes(const struct spi_nor *nor, const u32 settings
>>               return 4;
>>       case SMPT_CMD_ADDRESS_LEN_USE_CURRENT:
>>       default:
>> -             return nor->addr_nbytes;
>> +             return nor->params->addr_nbytes;
>>       }
>>  }
>>
>> @@ -689,7 +686,6 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
>>       u32 addr;
>>       int err;
>>       u8 i;
>> -     u8 addr_nbytes;
>>       u8 read_data_mask, map_id;
>>
>>       /* Use a kmalloc'ed bounce buffer to guarantee it is DMA-able. */
>> @@ -697,8 +693,6 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
>>       if (!buf)
>>               return ERR_PTR(-ENOMEM);
>>
>> -     addr_nbytes = nor->addr_nbytes;
>> -
>>       map_id = 0;
>>       /* Determine if there are any optional Detection Command Descriptors */
>>       for (i = 0; i < smpt_len; i += 2) {
>> @@ -753,8 +747,8 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
>>       /* fall through */
>>  out:
>>       kfree(buf);
>> -     nor->addr_nbytes = addr_nbytes;
>>       /* Restore setup to its uninitialized state. */
>> +     nor->addr_nbytes = 0;
> 
> Same as before, I don't think this function should know or care about
> the default or uninitialised values.
> 

well, maybe. nor->addr_nbytes comes with value zero when this method is called.
We gratuitously save it's zero value in a local variable and then we restore
it. The restore of the value could signify to the reader that nor->addr_nbytes
is already initialized with a sane value, which is not the case, so I find the
code more readable in my version. But I don't mind too much, so I'll drop this
particular change.

Thanks,
ta
 
>>       nor->read_dummy = 0;
>>       nor->read_opcode = 0;
>>       return ret;
>> @@ -1096,7 +1090,7 @@ static int spi_nor_parse_4bait(struct spi_nor *nor,
>>        * Spansion memory. However this quirk is no longer needed with new
>>        * SFDP compliant memories.
>>        */
>> -     nor->addr_nbytes = 4;
>> +     params->addr_nbytes = 4;
> 
> Patch looks good at first glance but I have not looked very carefully if
> it might cause some small issues.
> 
>>       nor->flags |= SNOR_F_4B_OPCODES | SNOR_F_HAS_4BAIT;
>>
>>       /* fall through */
>> --
>> 2.25.1
>>
> 
> issi.c's is25lp256_post_bfpt_fixups() also sets nor->addr_nbytes. Should
> that be updated to use params->addr_nbytes instead?
> 
> --
> Regards,
> Pratyush Yadav
> Texas Instruments Inc.

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