linux-kernel - Re: [PATCH v2 11/53] mtd: nand: denali: fix bitflips calculation in handle

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Date:   Thu, 23 Mar 2017 16:02:02 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     linux-mtd@...ts.infradead.org,
        Laurent Monat <laurent.monat@...uantique.com>,
        thorsten.christiansson@...uantique.com,
        Enrico Jorns <ejo@...gutronix.de>,
        Jason Roberts <jason.e.roberts@...el.com>,
        Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Graham Moore <grmoore@...nsource.altera.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Chuanxiao Dong <chuanxiao.dong@...el.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH v2 11/53] mtd: nand: denali: fix bitflips calculation in handle_ecc()

Hi Boris,

2017-03-23 5:57 GMT+09:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
> On Wed, 22 Mar 2017 23:07:18 +0900
> Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:
>
>> +     do {
>> +             err_addr = ioread32(denali->flash_reg + ECC_ERROR_ADDRESS);
>> +             err_sector = ECC_SECTOR(err_addr);
>> +             err_byte = ECC_BYTE(err_addr);
>> +
>> +             err_cor_info = ioread32(denali->flash_reg + ERR_CORRECTION_INFO);
>> +             err_cor_value = ECC_CORRECTION_VALUE(err_cor_info);
>> +             err_device = ECC_ERR_DEVICE(err_cor_info);
>> +
>> +             /* reset the bitflip counter when crossing ECC sector */
>> +             if (err_sector != prev_sector)
>> +                     bitflips = 0;
>> +
>> +             if (ECC_ERROR_UNCORRECTABLE(err_cor_info)) {
>> +                     /*
>> +                      * if the error is not correctable, need to look at the
>> +                      * page to see if it is an erased page. if so, then
>> +                      * it's not a real ECC error
>> +                      */
>> +                     ret = -EBADMSG;
>
> You should never return -EBADMSG directly. Just increment
> ecc_stats.failed and let the core return -EBADMSG to the upper layer.
>

Here, -EBADMSG is used like that returned from  ->ecc.correct()


Please notice denali_read_page() never returns -EBADMSG.

 -EBADMSG is used as a mark "we need erased page check".


I think nand_read_page_syndrome() does similar;
-EBADMSG is used internally.



-- 
Best Regards
Masahiro Yamada