[PATCH] ARM: imx8mq: reclock ARM PLL to 800MHz

[Sascha Hauer]

On Tue, Dec 29, 2020 at 09:23:28PM +0100, Lucas Stach wrote:
> The BootROM sets up the ARM PLL to run at 1.6GHz and then uses the
> divider after the PLL the achieve a CPU clock rate of 800MHz. New Linux
> kernels (>= 5.8) switch to a clock path that bypasses the divider, as
> the divider should not be used for CPU clock frequencies >1GHz. If the
> BootROM setup is left unchanged this causes the CPU clock to jump to
> the full 1.6GHz until CPUfreq takes over and reprograms the PLL. This
> rate is outside of the chip specification and leads to crashes.
> 
> Fix this by reclocking the ARM PLL to 800MHz.
> 
> Signed-off-by: Lucas Stach <dev at lynxeye.de>
> ---
>  arch/arm/dts/imx8mq.dtsi | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Applied, thanks

Sascha

> 
> diff --git a/arch/arm/dts/imx8mq.dtsi b/arch/arm/dts/imx8mq.dtsi
> index ec8347f38fa8..e56cdfe1308e 100644
> --- a/arch/arm/dts/imx8mq.dtsi
> +++ b/arch/arm/dts/imx8mq.dtsi
> @@ -17,7 +17,9 @@
>  			  <&clk IMX8MQ_CLK_USDHC2>,
>  			  <&clk IMX8MQ_CLK_ENET_AXI>,
>  			  <&clk IMX8MQ_CLK_ENET_TIMER>,
> -			  <&clk IMX8MQ_CLK_ENET_REF>;
> +			  <&clk IMX8MQ_CLK_ENET_REF>,
> +			  <&clk IMX8MQ_ARM_PLL>,
> +			  <&clk IMX8MQ_CLK_A53_DIV>;
>  
>  	assigned-clock-parents =  <&clk IMX8MQ_SYS1_PLL_400M>,
>  				  <&clk IMX8MQ_SYS1_PLL_400M>,
> @@ -29,5 +31,7 @@
>  			       <200000000>,
>  			       <266000000>,
>  			       <25000000>,
> -			       <125000000>;
> +			       <125000000>,
> +			       <800000000>,
> +			       <800000000>;
>  };
> -- 
> 2.29.2
> 
> 
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