linux-kernel - Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for Arasan NAND Flash Controller

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Date:   Wed, 12 Dec 2018 14:18:25 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Naga Sureshkumar Relli <nagasure@...inx.com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "richard@....at" <richard@....at>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "nagasuresh12@...il.com" <nagasuresh12@...il.com>,
        Michal Simek <michals@...inx.com>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>
Subject: Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for
 Arasan NAND Flash Controller

Hi Naga,

Naga Sureshkumar Relli <nagasure@...inx.com> wrote on Wed, 12 Dec 2018
13:07:42 +0000:

> Hi Miquel,
> 
> > -----Original Message-----
> > From: Miquel Raynal [mailto:miquel.raynal@...tlin.com]
> > Sent: Wednesday, December 12, 2018 2:40 PM
> > To: Naga Sureshkumar Relli <nagasure@...inx.com>
> > Cc: Boris Brezillon <boris.brezillon@...tlin.com>; robh@...nel.org; richard@....at; linux-
> > kernel@...r.kernel.org; marek.vasut@...il.com; linux-mtd@...ts.infradead.org;
> > nagasuresh12@...il.com; Michal Simek <michals@...inx.com>;
> > computersforpeace@...il.com; dwmw2@...radead.org
> > Subject: Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for Arasan
> > NAND Flash Controller
> > 
> > Hi Naga,
> > 
> > Naga Sureshkumar Relli <nagasure@...inx.com> wrote on Wed, 12 Dec 2018
> > 09:04:16 +0000:
> >   
> > > Hi Miquel,
> > >  
> > > > -----Original Message-----
> > > > From: Miquel Raynal [mailto:miquel.raynal@...tlin.com]
> > > > Sent: Wednesday, December 12, 2018 1:42 PM
> > > > To: Naga Sureshkumar Relli <nagasure@...inx.com>
> > > > Cc: Boris Brezillon <boris.brezillon@...tlin.com>; robh@...nel.org;
> > > > richard@....at; linux- kernel@...r.kernel.org;
> > > > marek.vasut@...il.com; linux-mtd@...ts.infradead.org;
> > > > nagasuresh12@...il.com; Michal Simek <michals@...inx.com>;
> > > > computersforpeace@...il.com; dwmw2@...radead.org
> > > > Subject: Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support
> > > > for Arasan NAND Flash Controller
> > > >
> > > > Hi Naga,
> > > >
> > > > Naga Sureshkumar Relli <nagasure@...inx.com> wrote on Wed, 12 Dec
> > > > 2018
> > > > 05:27:03 +0000:
> > > >  
> > > > > Hi Boris & Miquel,
> > > > >
> > > > > An update to my comments on thread https://lkml.org/lkml/2018/11/15/656.
> > > > > In this I said, will take a default error count value as 16 and
> > > > > during page read, will check the error count Register value with
> > > > > this and if it is equal to or greater than the default count(16) then I am checking for  
> > Erased pages.  
> > > > > But bit[7:0] in ECC_Error_Count_Register(0x38) will update for each error occurred.
> > > > > Link:
> > > > > https://www.xilinx.com/html_docs/registers/ug1087/ug1087-zynq-ultr
> > > > > ascale-  
> > > > registers.html and check for NAND module, ECC_Error_Count_Register.  
> > > > >
> > > > > I mean previously I dependent on Total error count value
> > > > > (bit[16:8]), but we can simply check for bit[7:0] To see the error occurred or not.
> > > > > I tried with this approach and I don't see any issues with that.
> > > > > I ran ubifs with this and I am able to see the bit[7:0] count is
> > > > > updated for erased page read and then will Use
> > > > > nand_chech_erased_ecc_chunk() to see the  
> > > > bitflips.  
> > > > >
> > > > > If it is ok, I will update the driver and will send new patch, but
> > > > > do you have any other  
> > > > comments on v12?
> > > >
> > > > Is 'nandbiterrs -i' running correctly now?  
> > > Yes, but with some changes in driver.
> > > I have added the log and changes done in https://lkml.org/lkml/2018/11/23/705.  
> > 
> > No, I don't see a working nandbiterrs there, sorry.  
> The log that I have attached is from mtd_nandbiterrs test
> So as per ARASAN controller ECC mechanism, it will correct upto 24-bit. After that the test will fail.

There is a distinction between:
1/ The driver fails to correct more than 24-bit and advertise the
   caller that the page read is somehow corrupted.
2/ The driver fails to correct more than 24-bit but does not complain
   about it. In our case, the caller (the test tool) will compare the
   page written and read: if it do not match it means the driver is
   broken because the driver reported a successful operation despite
   the fact that it returned a corrupted page.

You are in the second case, we expect the driver to behave like in 1/.

> 
> I am running mtd-utils nandbiterr test now. Will let you know once I completed that.

Yes please, prefer using the userspace tools.


Thanks,
Miquèl