Re: [PATCH v7 01/16] clk: tegra: Add binding for the Tegra124 DFLL clocksource

From: Tuomas Tynkkynen
Date: Mon Feb 16 2015 - 02:11:15 EST

On 02/13/2015 12:42 AM, Thierry Reding wrote:
On Thu, Jan 08, 2015 at 03:22:04PM +0200, Mikko Perttunen wrote:
From: Tuomas Tynkkynen <ttynkkynen@xxxxxxxxxx>

The DFLL is the main clocksource for the fast CPU cluster on Tegra124
and also provides automatic CPU rail voltage scaling as well. The DFLL
is a separate IP block from the usual Tegra124 clock-and-reset
controller, so it gets its own node in the device tree.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@xxxxxxxxxx>
Signed-off-by: Mikko Perttunen <mikko.perttunen@xxxxxxxx>
.../bindings/clock/nvidia,tegra124-dfll.txt | 69 ++++++++++++++++++++++
1 file changed, 69 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/nvidia,tegra124-dfll.txt

+Required properties:
+- compatible : should be "nvidia,tegra124-dfll-fcpu"
+- reg : Defines the following set of registers, in the order listed:
+ - registers for the DFLL control logic.
+ - registers for the I2C output logic.
+ - registers for the integrated I2C master controller.
+ - look-up table RAM for voltage register values.

Why do these all need to be separate sets? According to the TRM this is
a single IP block with a single register region, why the need to split
them apart?

On Tegra132, some of those register blocks (IIRC the first one) has moved to a different place (somewhere in the CAR register area). The TRM description indeed gives a single list of registers for the Tegra124 implementation of the DFLL. The split into 4 blocks was to make the binding more future-proof and to be closer to the real hardware design.
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