linux-kernel - Re: [PATCH v3 1/3] mtd: rawnand: denali_dt: add more clocks based on IP datasheet

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Message-ID: <20180619111444.5303c8ed@xps13>
Date:   Tue, 19 Jun 2018 11:14:44 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>, linux-kbuild@...r.kernel.org,
        Richard Weinberger <richard@....at>,
        "linux-stable #4 . 14+" <stable@...r.kernel.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v3 1/3] mtd: rawnand: denali_dt: add more clocks based
 on IP datasheet

On Fri, 15 Jun 2018 10:18:50 +0900, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:

> According to the Denali User's Guide, this IP needs three clocks:
> 
>  - clk: controller core clock
> 
>  - clk_x: bus interface clock
> 
>  - ecc_clk: clock at which ECC circuitry is run
> 
> Currently, denali_dt.c requires a single anonymous clock and its
> frequency.  However, the driver needs to get the frequency of "clk_x"
> not "clk".  This is confusing because people tend to assume the
> anonymous clock means the core clock.  In fact, I got a report of
> SOCFPGA breakage because the timing parameters are calculated based
> on a wrong frequency.
> 
> Instead of the cheesy implementation, the clocks in the real hardware
> should be represented in the driver and the DT-binding.
> 
> However, adding new clocks would break the existing platforms.  For the
> backward compatibility, the driver still accepts a single clock just as
> before.  If clk_x is missing, clk_x_rate is set to a hardcoded value.
> This is fine for existing DT of Socionext UniPhier, and also fixes the
> issue of Altera (Intel) SOCFPGA because both platforms use 200 MHz for
> the bus interface clock.
> 
> Fixes: 1bb88666775e ("mtd: nand: denali: handle timing parameters by setup_data_interface()")
> Cc: linux-stable <stable@...r.kernel.org> #4.14+
> Reported-by: Richard Weinberger <richard@....at>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 

Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks,
Miquèl