[4/7] dt-bindings: chosen: Add clocksource and clockevent selection
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Message ID 1568123236-767-5-git-send-email-claudiu.beznea@microchip.com
State Needs Review / ACK
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  • add support for clocksource/clockevent DT selection
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Commit Message

Claudiu Beznea Sept. 10, 2019, 1:47 p.m. UTC
From: Alexandre Belloni <alexandre.belloni@bootlin.com>

Some timer drivers may behave either as clocksource or clockevent
or both. Until now, in case of platforms with multiple hardware
resources of the same type, the drivers were chosing the first
registered hardware resource as clocksource/clockevent and the
next one as clockevent/clocksource. Other were using different
compatibles (one for each functionality, although its about the
same hardware). Add DT bindings to be able to choose the
functionality of a timer.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
 Documentation/devicetree/bindings/chosen.txt | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Comments

Neil Armstrong Sept. 11, 2019, 7:34 a.m. UTC | #1
Hi,

On 10/09/2019 15:47, Claudiu Beznea wrote:
> From: Alexandre Belloni <alexandre.belloni@bootlin.com>
> 
> Some timer drivers may behave either as clocksource or clockevent
> or both. Until now, in case of platforms with multiple hardware
> resources of the same type, the drivers were chosing the first
> registered hardware resource as clocksource/clockevent and the
> next one as clockevent/clocksource. Other were using different
> compatibles (one for each functionality, although its about the
> same hardware). Add DT bindings to be able to choose the
> functionality of a timer.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
>  Documentation/devicetree/bindings/chosen.txt | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
> index 45e79172a646..aad3034cdbdf 100644
> --- a/Documentation/devicetree/bindings/chosen.txt
> +++ b/Documentation/devicetree/bindings/chosen.txt
> @@ -135,3 +135,23 @@ e.g.
>  		linux,initrd-end = <0x82800000>;
>  	};
>  };
> +
> +linux,clocksource and linux,clockevent
> +--------------------------------------
> +
> +Those nodes have a timer property. This property is a phandle to the timer to be
> +chosen as the clocksource or clockevent. This is only useful when the platform
> +has multiple identical timers and it is not possible to let linux make the
> +correct choice.
> +
> +/ {
> +	chosen {
> +		linux,clocksource {
> +			timer = <&timer0>;
> +		};
> +
> +		linux,clockevent {
> +			timer = <&timer1>;
> +		};
> +	};
> +};
> 

Why not in aliases ?

aliases {
    clocksource0 = &timer0;
    clockevent0 = &timer1;
};

since we can have multiple of each, we should not limit ourselves to 1 clkevent
and 1 clksource.

In the aliases case, each driver would expose both capabilities, and the core would select
what to enable.

Neil

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index 45e79172a646..aad3034cdbdf 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt
@@ -135,3 +135,23 @@  e.g.
 		linux,initrd-end = <0x82800000>;
 	};
 };
+
+linux,clocksource and linux,clockevent
+--------------------------------------
+
+Those nodes have a timer property. This property is a phandle to the timer to be
+chosen as the clocksource or clockevent. This is only useful when the platform
+has multiple identical timers and it is not possible to let linux make the
+correct choice.
+
+/ {
+	chosen {
+		linux,clocksource {
+			timer = <&timer0>;
+		};
+
+		linux,clockevent {
+			timer = <&timer1>;
+		};
+	};
+};