linux-kernel - Re: [PATCH v3 6/9] mtd: spi-nor: core: Add helpers to read/write any register

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Date:   Tue, 19 Apr 2022 12:08:09 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>
CC:     <p.yadav@...com>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Nicolas.Ferre@...rochip.com>,
        <Takahiro.Kuwano@...ineon.com>
Subject: Re: [PATCH v3 6/9] mtd: spi-nor: core: Add helpers to read/write any
 register

On 4/19/22 14:46, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Am 2022-04-19 13:19, schrieb Michael Walle:
>> Am 2022-04-11 11:10, schrieb Tudor Ambarus:
>>> There are manufacturers that use registers indexed by address. Some of
>>> them support "read/write any register" opcodes. Provide core methods
>>> that
>>> can be used by all manufacturers. SPI NOR controller ops are
>>> intentionally
>>> not supported as we intend to move all the SPI NOR controller drivers
>>> under the SPI subsystem.
>>>
>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
>>> Tested-by: Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>
>>> Reviewed-by: Pratyush Yadav <p.yadav@...com>
>>
>> I still don't like it because the function doesn't do
>> anything what the function name might suggest. The read
>> just executes an op, the write executes an op with a
>> write enable before. All the behavior is determined by the
>> 'op' argument.
>>
>> Anyway,
>> Reviewed-by: Michael Walle <michael@...le.cc>
>>
>>> ---
>>> v3: no changes
>>>
>>>  drivers/mtd/spi-nor/core.c | 41
>>> ++++++++++++++++++++++++++++++++++++++
>>>  drivers/mtd/spi-nor/core.h |  4 ++++
>>>  2 files changed, 45 insertions(+)
>>>
>>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>>> index 6165dc7bfd17..42794328d3b6 100644
>>> --- a/drivers/mtd/spi-nor/core.c
>>> +++ b/drivers/mtd/spi-nor/core.c
>>> @@ -307,6 +307,47 @@ ssize_t spi_nor_write_data(struct spi_nor *nor,
>>> loff_t to, size_t len,
>>>      return nor->controller_ops->write(nor, to, len, buf);
>>>  }
>>>
>>> +/**
>>> + * spi_nor_read_reg() - read register to flash memory
>>> + * @nor:        pointer to 'struct spi_nor'.
>>> + * @op:             SPI memory operation. op->data.buf must be DMA-able.
>>> + * @proto:  SPI protocol to use for the register operation.
>>> + *
>>> + * Return: zero on success, -errno otherwise
>>> + */
>>> +int spi_nor_read_reg(struct spi_nor *nor, struct spi_mem_op *op,
>>> +                 enum spi_nor_protocol proto)
>>> +{
>>> +    if (!nor->spimem)
>>> +            return -EOPNOTSUPP;
>>> +
>>> +    spi_nor_spimem_setup_op(nor, op, proto);
>>> +    return spi_nor_spimem_exec_op(nor, op);
>>> +}
>>> +
>>> +/**
>>> + * spi_nor_write_reg() - write register to flash memory
>>> + * @nor:        pointer to 'struct spi_nor'
>>> + * @op:             SPI memory operation. op->data.buf must be DMA-able.
>>> + * @proto:  SPI protocol to use for the register operation.
>>> + *
>>> + * Return: zero on success, -errno otherwise
>>> + */
>>> +int spi_nor_write_reg(struct spi_nor *nor, struct spi_mem_op *op,
>>> +                  enum spi_nor_protocol proto)
>>> +{
>>> +    int ret;
>>> +
>>> +    if (!nor->spimem)
>>> +            return -EOPNOTSUPP;
>>> +
>>> +    ret = spi_nor_write_enable(nor);
>>> +    if (ret)
>>> +            return ret;
>>> +    spi_nor_spimem_setup_op(nor, op, proto);
>>> +    return spi_nor_spimem_exec_op(nor, op);
> 
> After seeing your next two patches. Shouldn't the
> spi_nor_wait_until_ready() call be here too?
> 

I thought of this too, but seems that for a reason that I don't
remember, we don't call for spi_nor_wait_until_ready after we
write the octal DTR bit. Pratyush, do you remember why?

Thanks,
ta