linux-kernel - Re: [PATCH] ARM: dts: at91: sama5d2: use the divided clock for SMC

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Date:   Tue, 20 Nov 2018 18:16:12 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Romain Izard <romain.izard.pro@...il.com>
Cc:     Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Tudor Ambarus <Tudor.Ambarus@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: at91: sama5d2: use the divided clock for SMC

Hello Romain,

On 20/11/2018 17:57:37+0100, Romain Izard wrote:
> The SAMA5D2 is different from SAMA5D3 and SAMA5D4, as there are two
> different clocks for the peripherals in the SoC. The Static Memory
> controller is connected to the divided master clock.
> 
> Unfortunately, the device tree does not correctly show this and uses the
> master clock directly. This clock is then used by the code for the NAND
> controller to calculate the timings for the controller, and we end up with
> slow NAND Flash access.
> 
> Fix the device tree, and the performance of Flash access is improved.
> 
> Signed-off-by: Romain Izard <romain.izard.pro@...il.com>
> ---
>  arch/arm/boot/dts/sama5d2.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/boot/dts/sama5d2.dtsi b/arch/arm/boot/dts/sama5d2.dtsi
> index 61f68e5c48e9..b405992eb601 100644
> --- a/arch/arm/boot/dts/sama5d2.dtsi
> +++ b/arch/arm/boot/dts/sama5d2.dtsi
> @@ -308,7 +308,7 @@
>  				  0x1 0x0 0x60000000 0x10000000
>  				  0x2 0x0 0x70000000 0x10000000
>  				  0x3 0x0 0x80000000 0x10000000>;
> -			clocks = <&mck>;
> +			clocks = <&h32ck>;

You will have to rebase on top of at91-dt. And if I'm not mistaken, this
line should be:

+			clocks = <&pmc PMC_TYPE_CORE PMC_MCK2>;

>  			status = "disabled";
>  
>  			nand_controller: nand-controller {
> -- 
> 2.17.1
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com