linux-kernel - Re: [PATCH] spi-nor: add support for is25wp256d

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Message-ID: <mhng-0f1dbb5d-9aa3-41c1-9cd6-c1f79b09ee4b@palmer-si-x1c4>
Date:   Mon, 06 Aug 2018 13:58:54 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     marek.vasut@...il.com
CC:     linux-mtd@...ts.infradead.org, dwmw2@...radead.org,
        computersforpeace@...il.com, boris.brezillon@...tlin.com,
        richard@....at, linux-kernel@...r.kernel.org,
        Wesley Terpstra <wesley@...ive.com>
Subject:     Re: [PATCH] spi-nor: add support for is25wp256d

On Sat, 04 Aug 2018 02:27:54 PDT (-0700), marek.vasut@...il.com wrote:
> On 08/04/2018 03:49 AM, Palmer Dabbelt wrote:
>> From: "Wesley W. Terpstra" <wesley@...ive.com>
>>
>> This is used of the HiFive Unleashed development board.
>>
>> Signed-off-by: Wesley W. Terpstra <wesley@...ive.com>
>> Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
>> ---
>>  drivers/mtd/spi-nor/spi-nor.c | 47 ++++++++++++++++++++++++++++++++++++++++++-
>>  include/linux/mtd/spi-nor.h   |  2 ++
>>  2 files changed, 48 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index d9c368c44194..e9a3557a3c23 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -1072,6 +1072,9 @@ static const struct flash_info spi_nor_ids[] = {
>>  			SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
>>  	{ "is25wp128",  INFO(0x9d7018, 0, 64 * 1024, 256,
>>  			SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
>> +	{ "is25wp256d", INFO(0x9d7019, 0, 32 * 1024, 1024,
>
> Is there a reason for the trailing 'd' in is25wp256d ? I'd drop it.

I'm honestly not sure.  There are data sheets for both of them, but I don't see 
much of a difference

    http://www.issi.com/WW/pdf/IS25LP(WP)256D.pdf
    http://www.issi.com/WW/pdf/25LP-WP256.pdf

Following the pattern, I'd expect to see

        { "is25wp256",  INFO(0x9d7019, 0, 64 * 1024, 512,
                        SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },

versus

        { "is25wp256d", INFO(0x9d7019, 0, 32 * 1024, 1024,
                        SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ | SPI_NOR_4B_OPCODES)
        },

So in other words: the d less sections that are larger, and also has the 4B 
opcodes flag set.  From the documentation in looks like the non-d version 
supports 3 and 4 byte opcodes, so I guess it's just a different physical 
layout?

In the data sheet for both I see

    "Pages can be erased in groups of 4Kbyte sectors, 32Kbyte blocks, 64Kbyte 
    blocks, and/or the entire chip"

which indicates to me that maybe we've just selected the larger section size?  If 
so then I'll change it to the first one in the new patch.

>> +	                SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ | SPI_NOR_4B_OPCODES)
>> +	},
>>
>>  	/* Macronix */
>>  	{ "mx25l512e",   INFO(0xc22010, 0, 64 * 1024,   1, SECT_4K) },
>> @@ -1515,6 +1518,45 @@ static int macronix_quad_enable(struct spi_nor *nor)
>>  	return 0;
>>  }
>>
>> +/**
>> + * issi_unlock() - clear BP[0123] write-protection.
>> + * @nor:	pointer to a 'struct spi_nor'
>> + *
>> + * Bits [2345] of the Status Register are BP[0123].
>> + * ISSI chips use a different block protection scheme than other chips.
>> + * Just disable the write-protect unilaterally.
>> + *
>> + * Return: 0 on success, -errno otherwise.
>> + */
>> +static int issi_unlock(struct spi_nor *nor)
>> +{
>> +	int ret, val;
>> +	u8 mask = SR_BP0 | SR_BP1 | SR_BP2 | SR_BP3;
>> +
>> +	val = read_sr(nor);
>> +	if (val < 0)
>> +		return val;
>> +	if (!(val & mask))
>> +		return 0;
>> +
>> +	write_enable(nor);
>> +
>> +	write_sr(nor, val & ~mask);
>> +
>> +	ret = spi_nor_wait_till_ready(nor);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = read_sr(nor);
>> +	if (ret > 0 && !(ret & mask)) {
>> +		dev_info(nor->dev, "ISSI Block Protection Bits cleared\n");
>> +		return 0;
>
> Is the dev_info() really needed ?

Nope.  I'll spin a v2 pending the above discussion.

>> +	} else {
>> +		dev_err(nor->dev, "ISSI Block Protection Bits not cleared\n");
>> +		return -EINVAL;
>> +	}
>> +}
>
> [...]

Thanks!