linux-kernel - Re: [PATCH] ARM: dts: at91: sama5d2 Xplained: add QSPI0 + SPI NOR memory nodes

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Message-ID: <20181211154033.076506aa@bbrezillon>
Date:   Tue, 11 Dec 2018 15:40:33 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     <Tudor.Ambarus@...rochip.com>
Cc:     <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <Ludovic.Desroches@...rochip.com>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <Cyrille.Pitchen@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mtd@...ts.infradead.org>, <broonie@...nel.org>,
        <linux-spi@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: at91: sama5d2 Xplained: add QSPI0 + SPI NOR
 memory nodes

On Mon, 10 Dec 2018 17:15:29 +0000
<Tudor.Ambarus@...rochip.com> wrote:

> From: Cyrille Pitchen <cyrille.pitchen@...rochip.com>
> 
> This patch configures the QSPI0 controller pin muxing and declares
> a jedec,spi-nor memory.
> 
> sama5d2 Xplained RevB and RevC use the Macronix MX25L25673G flash
> memory which advertises a maximum frequency of 80MHz for Quad IO
> Fast Read. Set the spi-max-frequency to 80MHz knowing that actually
> the QSPI drver will set the SPI bus clock to 166MHz / 3 = 55.3MHz.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...rochip.com>
> [tudor.ambarus@...rochip.com:
> - drop partitions,
> - add spi-rx/tx-bus-width
> - change spi-max-frequency to match the 80MHz limit advertised by
>   MX25L25673G for Quad IO Fast Read,
> - reword commit message and subject.]
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
> ---
>  arch/arm/boot/dts/at91-sama5d2_xplained.dts | 31 +++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/at91-sama5d2_xplained.dts b/arch/arm/boot/dts/at91-sama5d2_xplained.dts
> index 518e2b095ccf..171bc82cfbbf 100644
> --- a/arch/arm/boot/dts/at91-sama5d2_xplained.dts
> +++ b/arch/arm/boot/dts/at91-sama5d2_xplained.dts
> @@ -108,6 +108,21 @@
>  		};
>  
>  		apb {
> +			qspi0: spi@...20000 {
> +				pinctrl-names = "default";
> +				pinctrl-0 = <&pinctrl_qspi0_default>;
> +				/* status = "okay"; */ /* conflict with sdmmc1 */
> +
> +				flash@0 {
> +					compatible = "jedec,spi-nor";
> +					reg = <0>;
> +					spi-max-frequency = <80000000>;
> +					spi-tx-bus-width = <4>;
> +					spi-rx-bus-width = <4>;
> +					m25p,fast-read;
> +				};

I'm a bit lost. What's the point of defining this if the QSPI
controller is not enabled?