linux-kernel - Re: [PATCH 2/2] mtd: spi-nand: macronix: Add randomizer support

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Message-ID: <CAAyq3Saj5cmHAb3NPd=ZzJEvYD873s2CFKOyoxMrKk6Tj6yakg@mail.gmail.com>
Date: Fri, 5 Sep 2025 09:14:40 +0800
From: Cheng Ming Lin <linchengming884@...il.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: vigneshr@...com, linux-mtd@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, richard@....at, alvinzhou@...c.com.tw, 
	leoyu@...c.com.tw, Cheng Ming Lin <chengminglin@...c.com.tw>
Subject: Re: [PATCH 2/2] mtd: spi-nand: macronix: Add randomizer support

Hi Miquel,

Miquel Raynal <miquel.raynal@...tlin.com> 於 2025年8月18日 週一 下午4:47寫道：
>
> Hi Chang Ming,
>
> On 11/08/2025 at 11:01:25 +08, Cheng Ming Lin <linchengming884@...il.com> wrote:
>
> > Hi Miquel,
> >
> > Miquel Raynal <miquel.raynal@...tlin.com> 於 2025年8月8日 週五 下午6:19寫道：
> >>
> >> On 08/08/2025 at 17:55:03 +08, Cheng Ming Lin <linchengming884@...il.com> wrote:
> >>
> >> > From: Cheng Ming Lin <chengminglin@...c.com.tw>
> >> >
> >> > Enable randomizer function by specific flowchart to set the default value
> >> > of RANDEN to 1.
> >> >
> >> > Randomizer introduces two new DT properties for child nodes to configure
> >> > the randomizer functionality and coverage options.
> >> >  - mxic,enable-randomizer-otp: Specify whether to activate the randomizer
> >> >                                feature.
> >> >  - mxic,randopt: Define the randomizer area per page.
> >>
> >> Can we create a global NAND DT property for that? Enabling a randomizer
> >> is quite a generic step.
> >>
> >> > The penalty of randomizer are subpage accesses prohibited and more time
> >> > period is needed in program operation and entering deep power-down mode.
> >> > i.e., tPROG 320us to 360us (randomizer enabled).
> >>
> >> Do you want to share what is the added value in terms of lifetime to
> >> enable the randomizer, given the drawbacks which are significant?
> >
> > The randomizer mainly targets extremely unbalanced data patterns,
> > which might potentially lead to data errors.
> >
> > Please refer to the attached document:
> > https://www.mxic.com.tw/Lists/ApplicationNote/Attachments/2151/AN1051V1-The%20Introduction%20of%20Randomizer%20Feature%20on%20MX30xFxG28AD_MX35xFxG24AD.pdf
>
> Thanks for the link, it may be pointed with a "Link:" tag in your commit
> to further justify this addition. However it is sparse on details. I
> would be interested by more details, such as "how many 0s? how many
> bitflips? how often/likely?"

Thank you for your feedback. Unfortunately we do not have numerical
data such as exact numbers of '0's, bitflip rates, or occurrence
probabilities to share. Instead, I would like to refer to the JEDEC
JESD22-A117E qualification standard, which provides guidance on
retention and endurance testing.

According to this document, there is no single data pattern that
represents a universal worst-case across all failure mechanisms.
Different mechanisms may stress programmed cells, erased cells, or
cells influenced by adjacent states, and thus specific patterns such
as fully programmed, checkerboard, or mostly erased are each only
worst-case for certain designs or processes.

Given that no fixed pattern can cover all cases, the use of a
randomized data pattern is considered a practical mitigation
strategy. A randomizer distributes stress more evenly across the
device by scrambling incoming data before storage and restoring it
on read. This helps reduce pattern-dependent degradation and can
therefore improve long-term flash reliability.

>
> > Figure 1 shows that continuously programming too
> > many 0s can result in data errors.
>
> Thanks,
> Miquèl

Thanks,
Cheng-Ming Lin