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

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Message-ID: <ada61e0f-b512-e1ee-08fa-5bd287d695b5@microchip.com>
Date:   Tue, 19 Apr 2022 13:02:31 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>
CC:     <michael@...le.cc>, <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 15:32, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 19/04/22 12:08PM, Tudor.Ambarus@...rochip.com wrote:
>> 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?
> 
> We are not sure the protocol changed correctly so we can't rely on
> spi_nor_wait_until_ready(). We read the ID instead to be sure.
> 

But it is still recommended to check for the WIP bit, isn't it?

cheers,
ta