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Subject[PATCH RFC 3/8] dt-bindings: exynos: Add ASV tables binding documentation
Date
This patch adds documentation of the Exynos ASV (Adaptive Voltage Supply)
tables DT binding.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
---
.../devicetree/bindings/arm/samsung/asv.txt | 76 +++++++++++++++++++
1 file changed, 76 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/samsung/asv.txt

diff --git a/Documentation/devicetree/bindings/arm/samsung/asv.txt b/Documentation/devicetree/bindings/arm/samsung/asv.txt
new file mode 100644
index 000000000000..0db907263a91
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/samsung/asv.txt
@@ -0,0 +1,76 @@
+Exynos Adaptive Supply Voltage (ASV) tables
+-------------------------------------------
+
+The Adaptive Supply Voltage (ASV) on Exynos SoCs is a technique of adjusting
+operating points, i.e. the power supply voltage for given clock frequency,
+in order to better match actual capabilities of the hardware and optimize power
+consumption. This applies to subsystem of the SoC like: CPU clusters, GPU,
+the memory controller or camera ISP. During production process the SoC chip
+is assigned to one of several bins (ASV groups) and the group information
+is encoded in the SoC CHIPID block registers and/or OTP memory. This information
+is then used by the OS to select more finely matching operating points for
+devices.
+
+This binding describes data used to create actual operating points for the
+subsystems. The data is in form of two-dimensional arrays of M x N cells,
+where the first column contains frequency values and subsequent columns
+associated with ASV groups contain corresponding voltage values.
+
+ frequency group0 group1 ... group(N-1)
+ 0 1 2 ... N-1
+0 <f0 V00 V01 ... V0n>,
+1 <f1 V10 V11 ... V1n>,
+... < ... >,
+M-1 <fm Vm0 Vm1 ... Vmn>,
+
+In simplest form the actual operating points set may be created by selecting
+whole column for the voltage values, however also parts of multiple columns may
+be combined by the OS to create series of voltage values corresponding to
+frequencies in column 0.
+
+The ASV tables are defined as sub-nodes of parent node containing all tables.
+
+* Main node
+
+Required properties:
+ - compatible : should at least contain "samsung,exynos-asv-v1".
+
+* Table node
+
+Required properties:
+ - samsung,asv-table-size : specifies dimension of the table, the first cell is
+ total number of rows (M), the second cell is total number of columns (N),
+ - samsung,asv-table-id : ID of the table, lower 8-bits is an index (revision)
+ of the table, remaining bits (31...8) specify a subsystem the table applies
+ to: 0 - ARM/Eagle (big) CPU cluster, 1 - KFC (little) CPU cluster,
+ - samsung,asv-data : the ASV table data as described earlier in this document.
+ First cell is frequency value, then N-1 voltage values. Such sequence
+ is repeated M times.
+
+Optional properties:
+ - samsung,asv-common-data : a list of frequency, voltage pairs used to describe
+ operating points where voltage is same for all N-1 ASV groups. This allows
+ to avoid data duplication is the "samsung,asv-data" property.
+
+Example:
+
+&chipid {
+ asv {
+ compatible = "samsung,exynos-asv-v1";
+ asv-table-0 {
+ samsung,asv-table-size = <8 6>;
+ samsung,asv-table-id = <0x0>;
+ samsung,asv-data =
+ /* ASV0 ASV1 ASV2 ASV3 ASV4 */
+ <1700 1187500 1175000 1162500 1150000 1137500 >,
+ <1500 1125000 1112500 1100000 1087500 1075000 >,
+ <1300 1075000 1062500 1050000 1037500 1025000 >,
+ <1000 987500 975000 962500 950000 937500 >,
+ < 900 950000 937500 925000 925000 925000 >,
+ < 700 925000 912500 912500 912500 912500 >;
+ /* ASV0...15 */
+ samsung,asv-common-data = <600 900000>,
+ <500 900000>;
+ };
+ };
+};
--
2.17.1
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