Re: [PATCH v3 04/13] of: document new emc-timings subnode in nvidia,tegra124-car
From: Alexandre Courbot
Date: Fri Nov 07 2014 - 00:31:42 EST
On 11/07/2014 12:12 AM, Rob Herring wrote:
On Thu, Nov 6, 2014 at 12:37 AM, 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?
No, unit address should match a reg property.
Mmm, would you have any suggestion as to how this can be fixed? Right
now what I can think of is either to replace the "clock-frequency"
property by "reg" (which would be confusing), or to use a different
naming scheme, e.g. timing-12750000. IIUC the naming is not essential
for properly parsing these nodes, so maybe the second solution is the
way to go?
+
+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 {
The comma here is wrong. Commas should be used when you have something
like PCI bus:dev:func for addressing.
compatible = "nvidia,tegra124-car";
- reg = <0x60006000 0x1000>;
+ reg = <0x0 0x60006000 0x0 0x1000>;
The number of cell's is really irrelevant to the example.
#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";
Why do you need both clocks and hardcoded values? clock-frequency is
the desired freq you want to set TEGRA124_CLK_PLL_P to?
That would be nvidia,parent-clock-frequency IIUC, while clock-frequency
is the resulting EMC clock.
The clocks property really belongs as part of the memory controller
node or a memory device node.
I would tend to agree here. Tomeu, does it make sense to move these
properties to the EMC driver instead?
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