Re: [PATCH v2 3/3] mtd: spi-nand: macronix: Add randomizer support

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Cheng Ming Lin <linchengming884@gmail.com>
Cc: richard@nod.at,  vigneshr@ti.com,  robh@kernel.org,
	 krzk+dt@kernel.org, conor+dt@kernel.org,
	 tudor.ambarus@linaro.org, mmkurbanov@salutedevices.com,
	 Takahiro.Kuwano@infineon.com, pratyush@kernel.org,
	 linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
	 linux-kernel@vger.kernel.org, alvinzhou@mxic.com.tw,
	 Cheng Ming Lin <chengminglin@mxic.com.tw>
Subject: Re: [PATCH v2 3/3] mtd: spi-nand: macronix: Add randomizer support
Date: Wed, 10 Sep 2025 11:43:14 +0200	[thread overview]
Message-ID: <87ldmmd4nh.fsf@bootlin.com> (raw)
In-Reply-To: <CAAyq3SamY9vjQubd0BjpLb7J_W6JfKyyd987y+UioMV7UQ=94Q@mail.gmail.com> (Cheng Ming Lin's message of "Wed, 10 Sep 2025 17:26:13 +0800")

On 10/09/2025 at 17:26:13 +08, Cheng Ming Lin <linchengming884@gmail.com> wrote:

> Hi Miquel,
>
> Miquel Raynal <miquel.raynal@bootlin.com> 於 2025年9月10日 週三 下午5:12寫道：
>>
>>
>> > +static int macronix_set_randomizer(struct spinand_device *spinand)
>> > +{
>> > +     struct spi_mem_op exec_op = SPINAND_PROG_EXEC_1S_1S_0_OP(0);
>> > +     struct nand_device *nand = spinand_to_nand(spinand);
>> > +     struct device_node *dn = nanddev_get_of_node(nand);
>> > +     int randopt, ret;
>> > +     u8 cfg, status;
>> > +
>> > +     ret = spinand_read_reg_op(spinand, MACRONIX_FEATURE_ADDR_RANDOMIZER, &cfg);
>> > +     if (ret)
>> > +             return ret;
>> > +     if (cfg)
>> > +             return 0;
>> > +
>> > +     cfg = MACRONIX_CFG_ENPGM | MACRONIX_CFG_RANDEN;
>> > +     randopt = of_property_read_bool(dn, "mxic,randopt");
>>
>> Isn't that a leftover?
>
> The property "mxic,randopt" corresponds to bit2 of the configuration
> register 0x10. Its purpose is to control whether the randomizer also
> covers the initial portion of the spare area.

Do we need a DT property for that?

In any case, it must be declared in the bindings (which I do not think
it is?).

> Since the randomizer feature is only documented in Macronix datasheets,
> it is not clear whether the "randopt" bit is used by all vendors. For
> this reason, the handling is placed inside macronix.c.

Didn't we discuss in the past of a volatile version for SPI NAND
devices? I thought we could use a volatile approach instead.

Thanks,
Miquèl

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