linux-kernel - Re: [PATCH 2/5] mtd: rawnand: qcom: remove driver specific block

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Message-ID: <453b3e058e972dc0644f06c2f0969802@codeaurora.org>
Date:   Fri, 09 Nov 2018 11:48:32 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     linux-arm-msm@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org, Richard Weinberger <richard@....at>,
        Andy Gross <andy.gross@...aro.org>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 2/5] mtd: rawnand: qcom: remove driver specific
 block_markbad function

On 2018-11-04 21:26, Boris Brezillon wrote:
> Hi Abhishek,
> 
> On Fri, 20 Jul 2018 15:03:48 +0200
> Boris Brezillon <boris.brezillon@...tlin.com> wrote:
> 
>> On Fri, 20 Jul 2018 17:46:38 +0530
>> Abhishek Sahu <absahu@...eaurora.org> wrote:
>> 
>> > Hi Boris,
>> >
>> > On 2018-07-19 03:13, Boris Brezillon wrote:
>> > > On Wed, 18 Jul 2018 23:23:50 +0200
>> > > Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>> > >
>> > >> Boris,
>> > >>
>> > >> Can you please check the change in qcom_nandc_write_oob() is
>> > >> valid? I think it is but as this is a bit of a hack I prefer double
>> > >> checking.
>> > >
>> > > Indeed, it's hack-ish.
>> > >
>> > >>
>> > >> Thanks,
>> > >> Miquèl
>> > >>
>> > >>
>> > >> Abhishek Sahu <absahu@...eaurora.org> wrote on Fri,  6 Jul 2018
>> > >> 13:21:56 +0530:
>> > >>
>> > >> > The NAND base layer calls write_oob() by setting bytes at
>> > >> > chip->badblockpos with value non 0xFF for updating bad block status.
>> > >> > The QCOM NAND controller skips the bad block bytes while doing normal
>> > >> > write with ECC enabled. When initial support for this driver was
>> > >> > added, the driver specific function was added temporarily for
>> > >> > block_markbad() with assumption to change for raw read in NAND base
>> > >> > layer. Moving to raw read for block_markbad() seems to take more time
>> > >> > so this patch removes driver specific block_markbad() function by
>> > >> > using following HACK in write_oob() function.
>> > >> >
>> > >> > Check for BBM bytes in OOB and accordingly do raw write for updating
>> > >> > BBM bytes in NAND flash or normal write for updating available OOB
>> > >> > bytes.
>> > >
>> > > Why don't we change that instead of patching the qcom driver to guess
>> > > when the core tries to mark a block bad? If you're afraid of breaking
>> > > existing drivers that might rely on the "write/read BBM in non-raw
>> > > mode" solution (I'm sure some drivers are), you can always add a new
>> > > flag in chip->options (NAND_ACCESS_BBM_IN_RAW_MODE) and only use raw
>> > > accessors when this flag is set.
>> > >
>> >
>> >   We started with that Only
>> >
>> >   http://patchwork.ozlabs.org/patch/508565/
>> >
>> >   and since we didn't conclude, we went for driver
>> >   specific bad block check and mark bad block functions.
>> >
>> >   Now, we wanted to get rid of driver specific functions
>> >
>> >   1. For bad block check, we found the way to get the BBM bytes
>> >      with ECC read. Controller updates BBM in separate register
>> >      which we can read and update the same in OOB. Patch #1 of
>> >      series does the same.
>> >
>> >   2. For bad block mark, there is no way to update in ECC mode
>> >      that's why we went for HACK to get rid of driver specific
>> >      function.
>> >
>> >   If adding flag is fine now then this HACK won't be required.
>> 
>> Yep. I'm fine with that. Can you rebase the patch you pointed out on 
>> top
>> of nand/next and move the flag to chip->options instead of
>> chip->bbt_options + prefix it with NAND_ instead of NAND_BBT_?
> 
> I'm currently trying to get rid of chip->block_bad() (now placed in
> chip->legacy.block_bad()), and I wanted to know if you were still
> planning to submit the changes we discussed in this thread. If you
> don't have time, please let me know and I'll try to do it.
> 

  Sorry Boris, I couldn't work on these patches.

  Currently, I am working on non open source projects so
  I can't submit any patches in open source till this project
  completion due to legal guidelines.

  If this is urgent then you can try. I will help in
  QCOM related stuffs and testing.

  Thanks,
  Abhishek