linux-kernel - Re: [PATCH RFC 2/3] mtd: rawnand: Add support Macronix Block Protection function

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Message-ID: <OFB4F10613.467EB346-ON48258494.0020403E-48258494.002550A2@mxic.com.tw>
Date:   Tue, 15 Oct 2019 14:47:34 +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,
        gregkh@...uxfoundation.org, juliensu@...c.com.tw,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        marcel.ziswiler@...adex.com, marek.vasut@...il.com, richard@....at,
        tglx@...utronix.de, vigneshr@...com
Subject: Re: [PATCH RFC 2/3] mtd: rawnand: Add support Macronix Block Protection
 function

Hi Miquel,

> > > > 
> > > > > Macronix AC series support using SET/GET_FEATURES to change
> > > > > Block Protection and Unprotection.
> > > > > 
> > > > > MTD default _lock/_unlock function replacement by manufacturer
> > > > > postponed initialization. 
> > > > 
> > > > Why would we do that?
> > > > 
> > > > Anyway your solution looks overkill, if we ever decide to
> > > > implement these hooks for raw nand, it is better just to not
> > > > overwrite them in nand_scan_tail() if they have been filled
> > > > previously (ie. by the manufacturer code). 
> > > 
> > > Actually you should add two NAND hooks that do the interface with 
the
> > > MTD hooks. In the NAND hooks, check that the request is to lock all 
the
> > > device, otherwise return -ENOTSUPP. 
> > 
> > sorry, can't get your point.
> > 
> > Because the NAND entire chip will be protected if PT(protection) pin 
> > is active high at power-on.
> 
> In your implementation of the locking, you should check that the
> locking request is over the entire device, unless you can lock a
> smaller portion of course.

yes, I can lock a smaller portion.
And at the power-on of device with PT pin at high voltage, all blocks are 
locked.
They have to be unlocked by set feature command.

> 
> > 
> > > 
> > > Then fill-in these two hooks from the manufacturer code, without the
> > > postponed init.
> > > 
> > 
> > But in the final of nand_scan_tail(), mtd->_lock/_unlock will be
> > filled by NULL, right ?
> 
> The NAND core should set mtd->_lock/_unlock() to NAND specific hooks so
> that the MTD layer is abstracted and and drivers do not see it. Then,
> in the NAND helper, either there is no specific hook defined by a
> manufacturer driver and you return -ENOTSUPP, or you execute the
> defined hook.

okay, patch specific manufacturer _lock/_unlock driver
in nand_manufacturer_init();

and in the final of nand_scan_tail()
if (!mtd->_lock)
        mtd->_lock = NULL;
if (!mtd->_unlock)
        mtd->_unlock = NULL;

thanks for your time and comments.
Mason

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