linux-kernel - Re: [PATCH] mtd: rawnand: Add Macronix NAND read retry and randomizer support

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Message-ID: <20190409114701.744c2c8c@collabora.com>
Date:   Tue, 9 Apr 2019 11:47:01 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     masonccyang@...c.com.tw
Cc:     bbrezillon@...nel.org, computersforpeace@...il.com,
        dwmw2@...radead.org, juliensu@...c.com.tw,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        marek.vasut@...il.com, miquel.raynal@...tlin.com, richard@....at,
        zhengxunli@...c.com.tw
Subject: Re: [PATCH] mtd: rawnand: Add Macronix NAND read retry and
 randomizer support

On Tue, 9 Apr 2019 17:35:39 +0800
masonccyang@...c.com.tw wrote:

> > > +
> > > +static const struct kobj_attribute sysfs_mxic_nand =
> > > +   __ATTR(nand_random, S_IRUGO | S_IWUSR,
> > > +          mxic_nand_rand_type_show,
> > > +          mxic_nand_rand_type_store);  
> > 
> > No, we don't want to expose that through a sysfs file, especially since
> > changing the randomizer config means making the NAND unreadable for
> > those that have used it before the change.
> >   
> 
> Our on-die randomizer is still readable from user after the function 
> is enabled.

You mean the memory is still readable no matter the randomizer state.
Not sure how that's possible, but okay.

> This randomizer is just like a internal memory cell 
> reliability enhanced.

Why don't you enable it by default then?

> It could be enable at any time with OTP bit function and that's why
> we patch it by sys-fs.

Sorry, but that's not a good reason to expose that through sysfs.