linux-kernel - Re: [PATCH 2/2] arc: axs10x: Fix ARC PGU default clock frequency

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Date:   Thu, 2 Mar 2017 17:35:52 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Jose Abreu <Jose.Abreu@...opsys.com>
CC:     Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH 2/2] arc: axs10x: Fix ARC PGU default clock frequency

Hi Jose,

On Wed, 2017-02-22 at 18:19 +0000, Jose Abreu wrote:
> Default clock frequency for ARC PGU does not match any
> existing HDMI mode, instead the default value matches a
> DVI mode. Change the clock frequency to 74.25MHz so that
> it matches HDMI mode 1280x720@...z
> 
> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: devicetree@...r.kernel.org
> Cc: linux-snps-arc@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  arch/arc/boot/dts/axs10x_mb.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arc/boot/dts/axs10x_mb.dtsi b/arch/arc/boot/dts/axs10x_mb.dtsi
> index 9d882b1..41cfb29 100644
> --- a/arch/arc/boot/dts/axs10x_mb.dtsi
> +++ b/arch/arc/boot/dts/axs10x_mb.dtsi
> @@ -51,7 +51,7 @@
>  			pguclk: pguclk {
>  				#clock-cells = <0>;
>  				compatible = "fixed-clock";
> -				clock-frequency = <74440000>;
> +				clock-frequency = <74250000>;
>  			};
>  		};

Looks good to me but I have to note that with this change in place
monitors that don't report [correct] EDID won't work just because
if EDID is missing Linux kernel calculates pixel clock on its
own and for 1280x720@60 it gets 74.40 MHz which obviously differs from
yours 74.25 MHz and so arc_pgu_crtc_atomic_check() returns -EINVAL.

But with the fix I just sent, see
http://lists.infradead.org/pipermail/linux-snps-arc/2017-March/002173.html
everything will work again.

And once Vlad's patch for AXS PLLs gets accepted we'll finally get
support of multiple modes on AXS10x boards.

That said...

Acked-by: Alexey Brodkin <abrodkin@...opsys.com>