linux-kernel - Re: [PATCH] ARM: dts: lpc32xx: Revert set default clock rate of HCLK PLL

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Date:   Fri, 10 May 2019 15:15:58 +0200
From:   Gregory CLEMENT <gregory.clement@...tlin.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Vladimir Zapolskiy <vz@...ia.com>
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sylvain Lemieux <slemieux.tyco@...il.com>
Subject: Re: [PATCH] ARM: dts: lpc32xx: Revert set default clock rate of HCLK PLL

Hi Alexandre,

> This reverts commit c17e9377aa81664d94b4f2102559fcf2a01ec8e7.
>
> The lpc32xx clock driver is not able to actually change the PLL rate as
> this would require reparenting ARM_CLK, DDRAM_CLK, PERIPH_CLK to SYSCLK,
> then stop the PLL, update the register, restart the PLL and wait for the
> PLL to lock and finally reparent ARM_CLK, DDRAM_CLK, PERIPH_CLK to HCLK
> PLL.
>
> Currently, the HCLK driver simply updates the registers but this has no
> real effect and all the clock rate calculation end up being wrong. This is
> especially annoying for the peripheral (e.g. UARTs, I2C, SPI).
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

Tested-by: Gregory CLEMENT <gregory.clement@...tlin.com>

Gregory

> ---
>  arch/arm/boot/dts/lpc32xx.dtsi | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/arch/arm/boot/dts/lpc32xx.dtsi b/arch/arm/boot/dts/lpc32xx.dtsi
> index 20b38f4ade37..a49c97e5a38a 100644
> --- a/arch/arm/boot/dts/lpc32xx.dtsi
> +++ b/arch/arm/boot/dts/lpc32xx.dtsi
> @@ -323,9 +323,6 @@
>  
>  					clocks = <&xtal_32k>, <&xtal>;
>  					clock-names = "xtal_32k", "xtal";
> -
> -					assigned-clocks = <&clk LPC32XX_CLK_HCLK_PLL>;
> -					assigned-clock-rates = <208000000>;
>  				};
>  			};
>  
> -- 
> 2.21.0
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com

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