linux-kernel - Re: [PATCH] arm: dts: socfpga: denali needs nand_x

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Message-ID: <3320422.EJ8D6C0VHL@blindfold>
Date:   Fri, 22 Jun 2018 17:58:46 +0200
From:   Richard Weinberger <richard@....at>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marek Vašut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Subject: Re: [PATCH] arm: dts: socfpga: denali needs nand_x_clk too

Masahiro,

Am Freitag, 22. Juni 2018, 16:37:21 CEST schrieb Masahiro Yamada:
> Hi Richard,
> 
> 
> 2018-06-19 21:07 GMT+09:00 Richard Weinberger <richard@....at>:
> > The denali NAND flash controller needs at least two clocks to operate,
> > nand_clk and nand_x_clk.
> > Since 1bb88666775e ("mtd: nand: denali: handle timing parameters by
> > setup_data_interface()") nand_x_clk is used to derive timing settings.
> >
> > Signed-off-by: Richard Weinberger <richard@....at>
> > ---
> > Strictly speaking denali needs a ecc_clk too, but AFAIK such a clock
> > is not present on this SoC.
> > But my SoCFPGA knowledge is very limited.
> >
> > Thanks,
> > //richard
> > ---
> >  arch/arm/boot/dts/socfpga.dtsi | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/boot/dts/socfpga.dtsi b/arch/arm/boot/dts/socfpga.dtsi
> > index 486d4e7433ed..562f7b375bbd 100644
> > --- a/arch/arm/boot/dts/socfpga.dtsi
> > +++ b/arch/arm/boot/dts/socfpga.dtsi
> > @@ -754,7 +754,8 @@
> >                         reg-names = "nand_data", "denali_reg";
> >                         interrupts = <0x0 0x90 0x4>;
> >                         dma-mask = <0xffffffff>;
> > -                       clocks = <&nand_clk>;
> > +                       clocks = <&nand_clk>, <&nand_x_clk>;
> > +                       clock-names = "nand", "nand_x";
> 
> 
> IMHO, this should be
> 
>                           clocks = <&nand_clk>, <&nand_x_clk>, <&nand_x_clk>;
>                           clock-names = "nand", "nand_x", "ecc";
> 
> 
> 
> A clock consumer (Denali in this case) should generally
> take the same number of clocks across SoCs.
> 
> It is just some SoCs tie clocks together.
> 
> It is the case for my UniPhier platform;
> "nand_x" and "ecc" are tied up because they are both 200MHz.
> 
> 
> SOCFPGA supports HW ECC correction, thus it surely needs ecc clock.

Good point!

Thanks,
//richard