linux-kernel - Re: [PATCH v3 3/3] mtd: rawnand: denali: optimize timing parameters for data interface

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Message-ID: <CAK7LNAR8QTP6nMuR9j5-+Yxg5yzP2Dyq-rKGN-MaYg8xgr-3Ng@mail.gmail.com>
Date:   Mon, 18 Jun 2018 22:53:17 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Richard Weinberger <richard@....at>
Cc:     linux-mtd <linux-mtd@...ts.infradead.org>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH v3 3/3] mtd: rawnand: denali: optimize timing parameters
 for data interface

Hi Richard,


2018-06-18 16:22 GMT+09:00 Richard Weinberger <richard@....at>:
> Am Freitag, 15. Juni 2018, 03:18:52 CEST schrieb Masahiro Yamada:
>> This commit improves the ->setup_data_interface() hook.
>>
>> The denali_setup_data_interface() needs the frequency of clk_x
>> and the ratio of clk_x / clk.
>>
>> The latter is currently hardcoded in the driver, like this:
>>
>>   #define DENALI_CLK_X_MULT       6
>>
>> The IP datasheet requires that clk_x / clk be 4, 5, or 6.  I just
>> chose 6 because it is the most defensive value, but it is not optimal.
>> By getting the clock rate of both "clk" and "clk_x", the driver can
>> compute the timing values more precisely.
>
> What datasheet do you have, is it public?

No.  Not available in public.

I got the datasheet
because Socionext (formerly, Panasonic) bought this IP.


> Mine clearly states that the factor is 4.
> "The frequency of nand_x_clk is four times the frequency of nand_clk."

I checked
"Denali NAND Flash Memory Controller User's Guide"
released by Denali.

I also get access to a newer version
"Cadence Design IP - NAND Flash Memory Controller User's Guide"
because Cadence acquired Denali.


My datasheet says:
"clk_x - Cadence NAND Flash Memory Controller bus
interface clock. This runs at a configured
multiple of clk as is phase aligned. Configured
multiple can be between 4-6 times."



Various parts of this IP are configurable.
Is yours talking about this IP,
or about a particular configuration for SOCFPGA?



>> To not break the existing platforms, the fallback value, 50 MHz is
>> provided.  It is true for all upstreamed platforms.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>
> Reviewed-by: Richard Weinberger <richard@....at>
>
> Thanks,
> //richard
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-- 
Best Regards
Masahiro Yamada