linux-kernel - Re: [PATCH v3 5/5] mtd: rawnand: brcmnand: Fix mtd oobsize

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Date:   Tue, 4 Jul 2023 17:50:28 -0700
From:   William Zhang <william.zhang@...adcom.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        Linux MTD List <linux-mtd@...ts.infradead.org>,
        f.fainelli@...il.com, rafal@...ecki.pl, kursad.oney@...adcom.com,
        joel.peshkin@...adcom.com, computersforpeace@...il.com,
        anand.gore@...adcom.com, dregan@...l.com, kamal.dasu@...adcom.com,
        tomer.yacoby@...adcom.com, dan.beygelman@...adcom.com,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        linux-kernel@...r.kernel.org,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Kamal Dasu <kdasu.kdev@...il.com>
Subject: Re: [PATCH v3 5/5] mtd: rawnand: brcmnand: Fix mtd oobsize

Hi Miquel,

On 07/04/2023 08:30 AM, Miquel Raynal wrote:
> Hi William,
> 
> william.zhang@...adcom.com wrote on Tue, 27 Jun 2023 12:37:38 -0700:
> 
>> brcmnand controller can only access the flash spare area up to certain
>> bytes based on the ECC level. It can be less than the actual flash spare
>> area size. For example, for many NAND chip supporting ECC BCH-8, it has
>> 226 bytes spare area. But controller can only uses 218 bytes. So brcmand
>> driver overrides the mtd oobsize with the controller's accessible spare
>> area size. When the nand base driver utilizes the nand_device object, it
>> resets the oobsize back to the actual flash spare aprea size from
>> nand_memory_organization structure and controller may not able to access
>> all the oob area as mtd advises.
>>
>> This change fixes the issue by overriding the oobsize in the
>> nand_memory_organization structure to the controller's accessible spare
>> area size.
> 
> I am clearly not a big fan of this solution. memorg should be and
> remain a read only object. Can you please find another solution?
> 
I was debating on this too but I don't see option because there is no 
other hooks after nanddev_init to set the mtd->oobsize as far as I can 
see and I see there were similar fixes for other controller drivers 
after the nand device object init was committed, for example:
Fixes: 629a442cad5f ("mtd: rawnand: Fill memorg during detection")

I will think through this again but I am open to any suggestion.

>>
>> Fixes: a7ab085d7c16 ("mtd: rawnand: Initialize the nand_device object")
>> Signed-off-by: William Zhang <william.zhang@...adcom.com>
>>
>> ---
>>
>> Changes in v3: None
>> Changes in v2: None
>>
>>   drivers/mtd/nand/raw/brcmnand/brcmnand.c | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> index 407bf79cbaf4..39c7f547db1f 100644
>> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> @@ -2647,6 +2647,8 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
>>   	struct nand_chip *chip = &host->chip;
>>   	const struct nand_ecc_props *requirements =
>>   		nanddev_get_ecc_requirements(&chip->base);
>> +	struct nand_memory_organization *memorg =
>> +		nanddev_get_memorg(&chip->base);
>>   	struct brcmnand_controller *ctrl = host->ctrl;
>>   	struct brcmnand_cfg *cfg = &host->hwcfg;
>>   	char msg[128];
>> @@ -2668,10 +2670,11 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
>>   	if (cfg->spare_area_size > ctrl->max_oob)
>>   		cfg->spare_area_size = ctrl->max_oob;
>>   	/*
>> -	 * Set oobsize to be consistent with controller's spare_area_size, as
>> -	 * the rest is inaccessible.
>> +	 * Set mtd and memorg oobsize to be consistent with controller's
>> +	 * spare_area_size, as the rest is inaccessible.
>>   	 */
>>   	mtd->oobsize = cfg->spare_area_size * (mtd->writesize >> FC_SHIFT);
>> +	memorg->oobsize = mtd->oobsize;
>>   
>>   	cfg->device_size = mtd->size;
>>   	cfg->block_size = mtd->erasesize;
> 
> 
> Thanks,
> Miquèl
> 

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