linux-kernel - Re: [PATCH] Add support for Macronix NAND randomizer

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Message-ID: <OFBC7B2DED.A4E37205-ON48258462.00332180-48258462.0033B2E6@mxic.com.tw>
Date:   Mon, 26 Aug 2019 17:24:41 +0800
From:   masonccyang@...c.com.tw
To:     "Miquel Raynal" <miquel.raynal@...tlin.com>
Cc:     bbrezillon@...nel.org, computersforpeace@...il.com,
        dwmw2@...radead.org, frieder.schrempf@...tron.de,
        juliensu@...c.com.tw, kstewart@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        marek.vasut@...il.com, richard@....at, tglx@...utronix.de,
        vigneshr@...com
Subject: Re: [PATCH] Add support for Macronix NAND randomizer

Hi Miquel,

> 
> Re: [PATCH] Add support for Macronix NAND randomizer
> 
> Hi Mason,
> 
> masonccyang@...c.com.tw wrote on Mon, 26 Aug 2019 10:52:31 +0800:
> 
> > Hi Miquel,
> > > 
> > > Mason Yang <masonccyang@...c.com.tw> wrote on Tue, 20 Aug 2019 
13:53:48
> > > +0800:
> > > 
> > > > Macronix NANDs support randomizer operation for user data 
scrambled,
> > > > which can be enabled with a SET_FEATURE.
> > > > 
> > > > User data written to the NAND device without randomizer is still 
> > readable
> > > > after randomizer function enabled.
> > > > The penalty of randomizer are NOP = 1 instead of NOP = 4 and more 
time 
> > period
> > > 
> > > please don't use 'NOP' here, use 'subpage accesses' instead, 
otherwise
> > > people might not understand what it means while it has a real 
impact.
> > > 
> > 
> > okay, understood. 
> > will fix it by next submitting.
> > 
> > > > is needed in program operation and entering deep power-down mode.
> > > > i.e., tPROG 300us to 340us(randomizer enabled)
> > > > 
> > > > If subpage write not available with hardware ECC, for example,
> > > > NAND chip options NAND_NO_SUBPAGE_WRITE be set in driver and
> > > > randomizer function is recommended for high-reliability.
> > > > Driver checks byte 167 of Vendor Blocks in ONFI parameter page 
table
> > > > to see if this high-reliability function is supported.
> > > > 
> > > 
> > > You did not flagged this patch as a v2 and forgot about the 
changelog. 
> > 
> > will fix, thank you.
> > 
> > > You did not listen to our comments in the last version neither. I 
was
> > > open to a solution with a specific DT property for warned users but 
I
> > > don't see it coming. 
> > 
> > Sorry I missed the previous version of "read-retry and randomizer 
support" 
> > patch. 
> > Specific DT property is a good method to control it.
> > 
> > For more high-reliability concern, randomizer is recommended to enable 
by 
> > default,
> > but sub-page write is not allowed when randomizer is enabled.
> > 
> > Since most of HW ECC did not support sub-page write and we think 
driver to 
> > check
> > chip options flags is another simple and good way to enable 
randomizer.
> 
> Sorry but this is wrong. Several controllers and NAND chips support
> subpages. And changing now the behavior with such chips would entirely
> break the concerned setups (see Boris answer about UBI complaining if
> the subpage size changes).

okay, I see.
thanks for your information.

I will patch it based on your comments in the last version.

> 
> Thanks,
> Miquèl

best regards,
Mason

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