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Message-ID: <4207d4eb-31d5-31c0-1a7f-67ec00b63f58@sholland.org>
Date:   Mon, 2 Jan 2023 09:59:29 -0600
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To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        Brian Norris <computersforpeace@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mtd@lists.infradead.org, linux-sunxi@lists.linux.dev
References: <20221229181526.53766-1-samuel@sholland.org>
 <20221229181526.53766-5-samuel@sholland.org> <20230102101132.66aa1a1d@xps-13>
From:   Samuel Holland <samuel@sholland.org>
Subject: Re: [PATCH 4/7] mtd: rawnand: sunxi: Fix ECC strength maximization
In-Reply-To: <20230102101132.66aa1a1d@xps-13>
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Hi Miquèl,

On 1/2/23 03:11, Miquel Raynal wrote:
> Hi Samuel,
> 
> samuel@sholland.org wrote on Thu, 29 Dec 2022 12:15:23 -0600:
> 
>> This is already accounted for in the subtraction for OOB, since the BBM
>> overlaps the first OOB dword. With this change, the driver picks the
>> same ECC strength as the vendor driver.
>>
>> Fixes: 4796d8655915 ("mtd: nand: sunxi: Support ECC maximization")
>> Signed-off-by: Samuel Holland <samuel@sholland.org>
>> ---
>>
>>  drivers/mtd/nand/raw/sunxi_nand.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
>> index 1bddeb1be66f..1ecf2cee343b 100644
>> --- a/drivers/mtd/nand/raw/sunxi_nand.c
>> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
>> @@ -1643,8 +1643,7 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
>>  		ecc->size = 1024;
>>  		nsectors = mtd->writesize / ecc->size;
>>  
>> -		/* Reserve 2 bytes for the BBM */
>> -		bytes = (mtd->oobsize - 2) / nsectors;
>> +		bytes = mtd->oobsize / nsectors;
> 
> I'm sorry but I don't think we can make this work. This change would
> break all existing users...

OK, it is not too much of an issue because I can manually specify the
ECC parameters in the devicetree. Do you think it makes sense to fix
this when adding new hardware variants/compatible strings?

Regards,
Samuel