linux-kernel - Re: [PATCH 5/8] arm64: dts: imx8mm-kontron: Fix CAN SPI clock frequency

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Message-ID: <20211005071230.GC20743@dragon>
Date:   Tue, 5 Oct 2021 15:12:31 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Frieder Schrempf <frieder@...s.de>
Cc:     devicetree@...r.kernel.org,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>, stable@...r.kernel.org,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH 5/8] arm64: dts: imx8mm-kontron: Fix CAN SPI clock
 frequency

On Thu, Sep 30, 2021 at 05:56:28PM +0200, Frieder Schrempf wrote:
> From: Frieder Schrempf <frieder.schrempf@...tron.de>
> 
> The MCP2515 can be used with an SPI clock of up to 10 MHz. Set the
> limit accordingly to prevent any performance issues caused by the
> really low clock speed of 100 kHz.

Could you share some testing result of this change?

> 
> Fixes: 21c4f45b335f ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")

It's really an optimization rather than fix, isn't it?

Shawn

> Cc: stable@...r.kernel.org
> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
> ---
>  arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
> index f2c8ccefd1bf..dbf11e03ecce 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
> @@ -98,7 +98,7 @@ can0: can@0 {
>  		clocks = <&osc_can>;
>  		interrupt-parent = <&gpio4>;
>  		interrupts = <28 IRQ_TYPE_EDGE_FALLING>;
> -		spi-max-frequency = <100000>;
> +		spi-max-frequency = <10000000>;
>  		vdd-supply = <&reg_vdd_3v3>;
>  		xceiver-supply = <&reg_vdd_5v>;
>  	};
> -- 
> 2.33.0
>