linux-kernel - Re: [PATCH 1/2] mtd: nand: add generic helpers to check, match, maximize ECC settings

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Date:   Thu, 18 May 2017 15:27:11 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     linux-mtd@...ts.infradead.org, Enrico Jorns <ejo@...gutronix.de>,
        Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Marek Vasut <marek.vasut@...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>,
        Brian Norris <computersforpeace@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH 1/2] mtd: nand: add generic helpers to check, match,
 maximize ECC settings

Hi Boris,



2017-05-15 20:54 GMT+09:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
> Hi Masahiro,
>
> Sorry for the late reply.
>
> On Mon, 8 May 2017 12:40:47 +0900
> Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:
>
>> Hi Boris,
>>
>>
>> 2017-04-29 1:32 GMT+09:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
>>
>> >> +     for (setting = caps->ecc_settings; setting->step; setting++) {
>> >> +             /* If chip->ecc.size is already set, respect it. */
>> >> +             if (chip->ecc.size && setting->step != chip->ecc.size)
>> >> +                     continue;
>> >> +
>> >> +             /* If chip->ecc.strength is already set, respect it. */
>> >> +             if (chip->ecc.strength &&
>> >> +                 setting->strength != chip->ecc.strength)
>> >> +                     continue;
>> >
>> > Hm, I don't get it. If chip->ecc.strength and chip->ecc.size are
>> > explicitly set, you should just call nand_check_ecc_caps() and skip
>> > nand_try_to_match_ecc_req(). Why would you call
>> > nand_try_to_match_ecc_req() in this case?
>>
>>
>> I want to call this function if
>> ecc.size is specified but ecc.strength is not
>> (or vice versa).
>
> That's not a valid combination. I accepted the case where
> nand-ecc-step-size is not defined in the DT just because sometime you
> only have one possible setting which is imposed by the controller. In
> this case ecc.size should be explicitly set by the driver not left to 0.
>
>>
>>
>> If both ecc.size and ecc.strength are already specified,
>> you are right, no need to call this function.
>> This function can check the sanity of the specified
>> combination of (step, strength), but this is the same
>> as what nand_check_ecc_caps() does.


I am working on the next version because I really need to
merge all of my Denali controller patches for my SoCs.


One question about this part.


       /* If chip->ecc.size is already set, respect it. */
       if (chip->ecc.size && step_size != chip->ecc.size)
               continue;

Does this make sense for nand_try_to_maximize_ecc()?

(In other words, can nand-ecc-maximize stand together with nand-ecc-step-size?)


-- 
Best Regards
Masahiro Yamada