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SubjectRe: [PATCH v3 04/13] of: document new emc-timings subnode in nvidia,tegra124-car
On 10/30/2014 01:22 AM, Tomeu Vizoso wrote:
> The EMC clock needs some extra information for changing its rate.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> ---
> .../bindings/clock/nvidia,tegra124-car.txt | 46 +++++++++++++++++++++-
> 1 file changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/clock/nvidia,tegra124-car.txt b/Documentation/devicetree/bindings/clock/nvidia,tegra124-car.txt
> index ded5d62..42e0588 100644
> --- a/Documentation/devicetree/bindings/clock/nvidia,tegra124-car.txt
> +++ b/Documentation/devicetree/bindings/clock/nvidia,tegra124-car.txt
> @@ -19,12 +19,35 @@ Required properties :
> In clock consumers, this cell represents the bit number in the CAR's
> array of CLK_RST_CONTROLLER_RST_DEVICES_* registers.
>
> +The node should contain a "emc-timings" subnode for each supported RAM type (see
> +field RAM_CODE in register PMC_STRAPPING_OPT_A), with its unit address being its
> +RAM_CODE.
> +
> +Required properties for "emc-timings" nodes :
> +- nvidia,ram-code : Should contain the value of RAM_CODE this timing set
> + is used for.
> +
> +Each "emc-timings" node should contain a "timing" subnode for every supported
> +EMC clock rate. The "timing" subnodes should have the clock rate in Hz as their
> +unit address.

This seems to be a quite liberal use of unit addresses (same in the next
patch) - is this allowed by DT?

> +
> +Required properties for "timing" nodes :
> +- clock-frequency : Should contain the memory clock rate to which this timing
> +relates.
> +- nvidia,parent-clock-frequency : Should contain the rate at which the current
> +parent of the EMC clock should be running at this timing.
> +- clocks : Must contain an entry for each entry in clock-names.
> + See ../clocks/clock-bindings.txt for details.
> +- clock-names : Must include the following entries:
> + - emc-parent : the clock that should be the parent of the EMC clock at this
> +timing.
> +
> Example SoC include file:
>
> / {
> - tegra_car: clock {
> + tegra_car: clock@0,60006000 {
> compatible = "nvidia,tegra124-car";
> - reg = <0x60006000 0x1000>;
> + reg = <0x0 0x60006000 0x0 0x1000>;
> #clock-cells = <1>;
> #reset-cells = <1>;
> };
> @@ -60,4 +83,23 @@ Example board file:
> &tegra_car {
> clocks = <&clk_32k> <&osc>;
> };
> +
> + clock@0,60006000 {
> + emc-timings@3 {
> + nvidia,ram-code = <3>;
> +
> + timing@12750000 {
> + clock-frequency = <12750000>;
> + nvidia,parent-clock-frequency = <408000000>;
> + clocks = <&tegra_car TEGRA124_CLK_PLL_P>;
> + clock-names = "emc-parent";
> + };
> + timing@20400000 {
> + clock-frequency = <20400000>;
> + nvidia,parent-clock-frequency = <408000000>;
> + clocks = <&tegra_car TEGRA124_CLK_PLL_P>;
> + clock-names = "emc-parent";
> + };
> + };
> + };

At first it seems confusing to see a top-level node without a compatible
property, until you realize it has already been defined before.

In patch 05, you put "Example board file:" above a similar node, which
is enough to lift that ambiguity - could you do the same here?


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