Re: [PATCH v3 04/13] of: document new emc-timings subnode in nvidia,tegra124-car
From: Alexandre Courbot
Date: Thu Nov 06 2014 - 04:16:11 EST
On 11/06/2014 06:11 PM, Tomeu Vizoso wrote:
On 6 November 2014 07:37, Alexandre Courbot <acourbot@xxxxxxxxxx> wrote:
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@xxxxxxxxxxxxx>
---
.../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?
Well, it's not that different from using the register address. I think
it helps with readability more than an arbitrary index.
+
+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?
Oh, actually it was already in the file. I took this idea from here
for patch 05.
My bad, missed it!
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