linux-kernel - Re: [PATCH] ARM: dts: r8a7791: Don't disable referenced optional clocks

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Date:	Thu, 7 Apr 2016 02:15:00 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Sjoerd Simons <sjoerd.simons@...labora.co.uk>,
	Simon Horman <horms@...ge.net.au>
Cc:	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: dts: r8a7791: Don't disable referenced optional
 clocks

On 04/06/2016 03:52 PM, Sjoerd Simons wrote:

> clk_get on a disabled clock node will return EPROBE_DEFER, which can
> cause drivers to be deferred forever if such clocks are referenced in
> their clocks property.
>
> Update the various disabled external clock nodes to default to a
> frequency of 0, but don't disable them to prevent this.
>
> Signed-off-by: Sjoerd Simons <sjoerd.simons@...labora.co.uk>
>
> ---
>
>   arch/arm/boot/dts/r8a7791-koelsch.dts | 1 +
>   arch/arm/boot/dts/r8a7791-porter.dts  | 1 +
>   arch/arm/boot/dts/r8a7791.dtsi        | 5 +----
>   3 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/boot/dts/r8a7791-koelsch.dts b/arch/arm/boot/dts/r8a7791-koelsch.dts
> index 1adf877..da59c28 100644
> --- a/arch/arm/boot/dts/r8a7791-koelsch.dts
> +++ b/arch/arm/boot/dts/r8a7791-koelsch.dts
> @@ -660,6 +660,7 @@
>   };
>
>   &pcie_bus_clk {
> +	clock-frequency = <100000000>;

    Hmmm, looking at the Koelsch schematics, I don't see this clock. :-/

>   	status = "okay";
>   };
>
> diff --git a/arch/arm/boot/dts/r8a7791-porter.dts b/arch/arm/boot/dts/r8a7791-porter.dts
> index 9554d13..19b257e 100644
> --- a/arch/arm/boot/dts/r8a7791-porter.dts
> +++ b/arch/arm/boot/dts/r8a7791-porter.dts
> @@ -413,6 +413,7 @@
>   };
>
>   &pcie_bus_clk {
> +	clock-frequency = <100000000>;
>   	status = "okay";
>   };
>

    Again, looking at the Porter schematics, I don't see this clock either. :-/

> diff --git a/arch/arm/boot/dts/r8a7791.dtsi b/arch/arm/boot/dts/r8a7791.dtsi
> index 8693888..676df63 100644
> --- a/arch/arm/boot/dts/r8a7791.dtsi
> +++ b/arch/arm/boot/dts/r8a7791.dtsi
> @@ -1104,8 +1104,7 @@
>   		pcie_bus_clk: pcie_bus {
>   			compatible = "fixed-clock";
>   			#clock-cells = <0>;
> -			clock-frequency = <100000000>;
> -			status = "disabled";
> +			clock-frequency = <0>;

    If the clock has a good default frequency, I don't think you need to 
remove it. Otherwise you missed USB_EXTAL which is 48 MHz (and can be overridden).

[...]

MBR, Sergei