linux-kernel - Re: [PATCH 0/3] mtd: Ingenic NAND fix for JZ4740

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Date:   Sun, 07 Nov 2021 18:43:33 +0000
From:   Paul Cercueil <paul@...pouillou.net>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Harvey Hunt <harveyhuntnexus@...il.com>, list@...ndingux.net,
        linux-mtd@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mips <linux-mips@...r.kernel.org>,
        Riccardo Mottola <riccardo.mottola@...ero.it>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, Paul Boddie <paul@...die.org.uk>
Subject: Re: [PATCH 0/3] mtd: Ingenic NAND fix for JZ4740

Hi Nikolaus,

Le dim., nov. 7 2021 at 14:47:43 +0100, H. Nikolaus Schaller 
<hns@...delico.com> a écrit :
> Hi Paul,
> 
>>  Am 09.10.2021 um 20:49 schrieb Paul Cercueil <paul@...pouillou.net>:
>> 
>>  Hi,
>> 
>>  Looks like NAND support has been broken on the JZ4740 SoC for a 
>> while;
> 
> Yes, I remember someone telling that something was fundamentally 
> broken
> and impossible to be fixed a while ago.

You mean MLC NAND, and that's still broken.

>>  it looks like it comes from the fact that the "hw_oob_first" 
>> mechanism
>>  was dropped from the NAND core and moved to the Davinci driver.
>> 
>>  It turns out the JZ4740 SoC needs it too; I didn't notice it when
>>  writing the new ingenic-nand driver (to replace the old jz4740-nand
>>  driver) most likely because my Device Tree had the "nand-ecc-mode" 
>> set
>>  to "hw_oob_first".
>> 
>>  I am not very sure about patch [1/3]; to me the original code does 
>> not
>>  make sense, and it didn't work out-of-the-box on the JZ4740 without 
>> it.
>>  By applying patch [1/3] the function 
>> nand_read_page_hwecc_oob_first()
>>  can be reused for the JZ4740 SoC as well. But I did not test patch 
>> [1/3]
>>  on Davinci.
> 
> would this also work for jz4780 NAND?

The JZ4780 NAND driver does work, but UBI refuses to use the CI20's 
NAND as it's a MLC.

-Paul