linux-kernel - Re: [PATCH v1] mtd: rawnand: Add Macronix NAND read retry support

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Date:   Tue, 14 May 2019 10:16:09 +0800
From:   masonccyang@...c.com.tw
To:     "Miquel Raynal" <miquel.raynal@...tlin.com>
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, richard@....at
Subject: Re: [PATCH v1] mtd: rawnand: Add Macronix NAND read retry support

Hi Miquel,

> > > > > > +
> > > > > > +      if (mxic->reliability_func & MACRONIX_READ_RETRY_BIT) {
> > > > > > +         chip->read_retries = MACRONIX_READ_RETRY_MODE + 1; 
> > > > > 
> > > > > Why +1 here, I am missing something? 
> > > > 
> > > > 
> > > > Without + 1, read retry mode is up to 4 rather than 5.
> > > > But this NAND device support read retry mode up to 5.
> > > > 
> > > 
> > > If there are 5 modes, you need to set 5 to chip->read_retries, not 
6.
> > > 
> > > If only 4 modes are used, there is probably a bug in the core that
> > > must be fixed, please do not workaround it in the driver! 
> > 
> > 
> > It seems some patches is needed in nand_base.c
> > 
-------------------------------------------------------------------------------------
> > diff --git a/drivers/mtd/nand/raw/nand_base.c 
> > b/drivers/mtd/nand/raw/nand_base.c
> > index ddd396e..56be3a9 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -3101,7 +3101,8 @@ static int nand_setup_read_retry(struct 
nand_chip 
> > *chip, int retry_mode)
> >  {
> >         pr_debug("setting READ RETRY mode %d\n", retry_mode);
> > 
> > -       if (retry_mode >= chip->read_retries)
> > +       if (retry_mode > chip->read_retries)
> 
> If I understand correctly, chip->read_retries is the total number of
> 'modes' so the last valid mode is indeed chip->read_retries -1.
> 
> I thought the problem would come from the core but I was wrong, you
> actually need a MACRONIX_NUM_READ_RETRY_MODES set to 6. Please have two
> defines if you need both (the first one being something like
> MACRONIX_MAXIMUM_READ_RETRY_MODE set to 5).

I have checked one of Micron's datasheet and it defined read-retry number 
= 8,
mode 0 ~ 7, 0 mean to disable read-retry.
Therefore, I will patch MACRONIX_NUM_READ_RETRY_MODES = 6.

thanks & best regards,
Mason

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This e-mail and any attachments may contain confidential information and/or personal data, which is protected by applicable laws. Please be reminded that duplication, disclosure, distribution, or use of this e-mail (and/or its attachments) or any part thereof is prohibited. If you receive this e-mail in error, please notify us immediately and delete this mail as well as its attachment(s) from your system. In addition, please be informed that collection, processing, and/or use of personal data is prohibited unless expressly permitted by personal data protection laws. Thank you for your attention and cooperation.

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