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From: Richard Weinberger <richard@nod.at>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-mtd@lists.infradead.org,
 Boris Brezillon <boris.brezillon@bootlin.com>,
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Subject: Re: [PATCH v3 3/3] mtd: rawnand: denali: optimize timing parameters
 for data interface
Date: Mon, 18 Jun 2018 09:22:44 +0200
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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?
Mine clearly states that the factor is 4.
"The frequency of nand_x_clk is four times the frequency of nand_clk."

> 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@socionext.com>

Reviewed-by: Richard Weinberger <richard@nod.at>

Thanks,
//richard