linux-kernel - Re: [PATCH] ARM: dts: meson8: Use a higher default GPU clock frequency

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Date:   Mon, 26 Jul 2021 09:56:50 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org
Cc:     khilman@...libre.com, jbrunet@...libre.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Demetris Ierokipides <ierokipides.dem@...il.com>
Subject: Re: [PATCH] ARM: dts: meson8: Use a higher default GPU clock
 frequency

On 11/07/2021 23:40, Martin Blumenstingl wrote:
> We are seeing "imprecise external abort (0x1406)" errors during boot
> (which then cause the whole board to hang) on Meson8 (but not Meson8m2).
> These are observed while trying to access the GPU's registers when the
> MALI clock is running at it's default setting of 24MHz. The 3.10 vendor
> kernel uses 318.75MHz as "default" GPU frequency. Using that makes the
> "imprecise external aborts" go away.
> Add the assigned-clocks and assigned-clock-rates properties to also bump
> the MALI clock to 318.75MHz before accessing any of it's registers.
> 
> Fixes: 7d3f6b536e72c9 ("ARM: dts: meson8: add the Mali-450 MP6 GPU")
> Reported-by: Demetris Ierokipides <ierokipides.dem@...il.com>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>  arch/arm/boot/dts/meson8.dtsi | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/meson8.dtsi b/arch/arm/boot/dts/meson8.dtsi
> index 157a950a55d3..686c7b7c79d5 100644
> --- a/arch/arm/boot/dts/meson8.dtsi
> +++ b/arch/arm/boot/dts/meson8.dtsi
> @@ -304,8 +304,13 @@ mali: gpu@...00 {
>  					  "pp2", "ppmmu2", "pp4", "ppmmu4",
>  					  "pp5", "ppmmu5", "pp6", "ppmmu6";
>  			resets = <&reset RESET_MALI>;
> +
>  			clocks = <&clkc CLKID_CLK81>, <&clkc CLKID_MALI>;
>  			clock-names = "bus", "core";
> +
> +			assigned-clocks = <&clkc CLKID_MALI>;
> +			assigned-clock-rates = <318750000>;
> +
>  			operating-points-v2 = <&gpu_opp_table>;
>  			#cooling-cells = <2>; /* min followed by max */
>  		};
> 

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>