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

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Message-ID: <OFF725800E.8B26D2E9-ON48258462.000B94B2-48258462.000FCB85@mxic.com.tw>
Date:   Mon, 26 Aug 2019 10:52:31 +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,
> 
> 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.

> 
> 
> Thanks,
> Miquèl

thanks for your time and comments.

best regards,
Mason

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