Mediatek MT8173 Quad Core big.LITTLE ARM Cortex A72/A53 Processor Code Submitted to Linux Mainline

[Update: MT8173 processor has now been announced, and it’s using Cortex A72 and A53 instead of A57/A53, as initially shown in the Linux kernel source code]

Mediatek is not exactly known to compliant with open source licences, or be involved with the open source community. But the company is certainly going into the right direction with their cooperation with Google leading to source code release for Android One smartphones, and the recently launched Mediatek Labs for community projects, starting with LinkIt One IoT platform. Mediatek is also regularly submitting code to the Linux ARM Kernel mailing list, and yesterday code was submitted for Mediatek MT8173 SoC, a 64-bit ARMv8 processor with two Cortex 53 and two Cortex 57 cores in big.LITTLE configuration. As far as I know, it could be the first Mediatek SoC with “big” Cortex A57 cores.

Code snippet from mt8173.dtsi related to CPU cores:

cpus {
+		#address-cells = &lt;1&gt;;
+		#size-cells = &lt;0&gt;;
+
+		cpu0: cpu@0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a53";
+			reg = &lt;0x000&gt;;
+			enable-method = "psci";
+		};
+
+		cpu1: cpu@1 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a53";
+			reg = &lt;0x001&gt;;
+			enable-method = "psci";
+		};
+
+		cpu2: cpu@2 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = &lt;0x100&gt;;
+			enable-method = "psci";
+		};
+
+		cpu3: cpu@3 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = &lt;0x101&gt;;
+			enable-method = "psci";
+		};
+	};

cpus {

+ #address-cells = <1>;

+ #size-cells = <0>;

+ cpu0: cpu@0 {

+ device_type = "cpu";

+ compatible = "arm,cortex-a53";

+ reg = <0x000>;

+ enable-method = "psci";

+ };

+ cpu1: cpu@1 {

+ device_type = "cpu";

+ compatible = "arm,cortex-a53";

+ reg = <0x001>;

+ enable-method = "psci";

+ };

+ cpu2: cpu@2 {

+ device_type = "cpu";

+ compatible = "arm,cortex-a57";

+ reg = <0x100>;

+ enable-method = "psci";

+ };

+ cpu3: cpu@3 {

+ device_type = "cpu";

+ compatible = "arm,cortex-a57";

+ reg = <0x101>;

+ enable-method = "psci";

+ };

A short DTS file was also submitted for MT8173 tablet EVB (evaluation board):

+#include "mt8173.dtsi"
+
+/ {
+	model = "mediatek,mt8173-evb";
+
+	aliases {
+		serial0 = &amp;uart0;
+		serial1 = &amp;uart1;
+		serial2 = &amp;uart2;
+		serial3 = &amp;uart3;
+	};
+
+	memory {
+		reg = &lt;0 0x40000000 0 0x40000000&gt;;
+	};
+};

+#include "mt8173.dtsi"

+/ {

+ model = "mediatek,mt8173-evb";

+ aliases {

+ serial0 = &uart0;

+ serial1 = &uart1;

+ serial2 = &uart2;

+ serial3 = &uart3;

+ };

+ memory {

+ reg = <0 0x40000000 0 0x40000000>;

+ };

+};

The memory section normally defines the location and size of the RAM (0x40000000 correspond to 1GB), but in this device tree file the location and size is shown twice, maybe because its a 64-bit platform addressed with 2x 1GB RAM (TBC) using 32-bit buses. An explanation of this would be welcomed.

That’s about all I know for know, except the new processor shares a lot with MT8135 and other MT65xx series. My search for MTK8173 / MT8173 did not yield interesting results so far.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.