Linux/AM5726: Power reduction in U-boot

Ronak Patel

Expert 1100 points

Part Number: AM5726

Tool/software: Linux

Hello,

I need to do power consumption at u-boot level as well as at kernel level.

How can I do the lowest OPP in u-boot?

At kernel level, I changed the governor in powersave mode.

Here powersave mode is running at 1GHz and maximum is 1.5GHz.

If I want to add lower than 1 GHz support in powersave mode how can I do?

I need to compromise boot time while OPP is low, but when the board will boot up, I will change the governor from powersave mode to ondemand mode.

Please do the needful.

Regards,

-- Ronak

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

The PM experts have been notified. They will respond here.

0 Pavel Botev over 6 years ago

TI__Guru**** 170625 points

Hi Ronak,

Do you use ti-processor-sdk-linux-am57xx-evm-03.03.00.04?

Ronak Patel said:
How can I do the lowest OPP in u-boot?

Lowest OPP for which domain (MPU, DSPEVE, IVA, GPU)? Regarding Cortex-A15 MPU, u-boot is using the lowest OPP (OPP_NOM) at 1000MHz. And these 1000MHz are the max frequency possible for OPP_NOM.

Or do you mean that you need to reduce this 1000MHz frequency in u-boot?

Ronak Patel said:
At kernel level, I changed the governor in powersave mode.

Ronak Patel said:
If I want to add lower than 1 GHz support in powersave mode how can I do?

You can update the OPP table according to your specific needs. See the below pointers:

http://processors.wiki.ti.com/index.php/Linux_Core_Power_Management_User's_Guide_%28v4.4%29#Operating_Points

Regards,
Pavel

0 Michael Erdahl over 6 years ago

TI__Genius 13455 points

Ronak,

In U-Boot, take a look at UBOOT/arch/arm/cpu/armv7/omap5/hw_data.c

Modify the crystal DPLL multiplier field for the crystal installed on your board. For example, I use the following to define a 500MHz MPU clock with a 20MHz crystal:

/* OPP NOM FREQUENCY for OMAP5 ES2.0, and DRA7 ES1.0 */
static const struct dpll_params mpu_dpll_params_1ghz[NUM_SYS_CLKS] = {
...
        {200, 3, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1},	/* 20 MHz   */
...
};

In the Linux kernel, you will need to start with modifying the cpu0_opp_table in LINUX/arch/arm/boot/dts/dra7.dtsi

In my experience it is slightly more tricky to add a new frequency, in addition to the frequencies already defined. For now, you can test replacing the 1.0GHz entry with one at 500MHz to characterize your power savings, and I can get back with you on further modifications to support 500MHz as a fourth frequency option.

BTW, do not modify the voltage below OPP_NOM - we do not define a lower voltage at 500MHz operation.

	cpu0_opp_table: opp_table0 {
		compatible = "operating-points-v2";
		opp-shared;

		opp_nom@500000000 {
			opp-hz = /bits/ 64 <500000000>;
			opp-microvolt = <1060000 850000 1150000>;
			opp-supported-hw = <0xFF 0x01>;
			opp-suspend;
		};

		opp_od@1176000000 {
			opp-hz = /bits/ 64 <1176000000>;
			opp-microvolt = <1160000 885000 1160000>;
			opp-supported-hw = <0xFF 0x02>;
		};

		opp_high@1500000000 {
			opp-hz = /bits/ 64 <1500000000>;
			opp-microvolt = <1210000 950000 1250000>;
			opp-supported-hw = <0xFF 0x04>;
		};
	};

Regards,
Mike

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Linux/AM5726: Power reduction in U-boot