2.3 config.txt Configuration File

RDK uses the configuration file config.txt to set system configurations during startup. config.txt is read during the uboot stage and supports modifications to device tree configurations, IO pin states, ION memory, CPU frequency, etc. This file is usually accessible from Linux at /boot/config.txt and must be edited as the root user. If the config.txt file does not exist but there are configuration settings, simply create it as a new text file.

Notes

Note

1. The config.txt configuration file is only applicable to the RDK X3、RDK X5 and RDK X3 Module development boards and not for the RDK Ultra development board.

2. The system version must be at least 2.1.0.

3. The miniboot version cannot be earlier than the version dated 20231126. Refer to rdk-miniboot-update for updating the miniboot on the board.

4. If you add filtering items to this configuration file, please note whether the configuration items will be filtered out when using the srpi-config tool.

Device Tree Configuration

dtdebug

If dtdebug is non-zero, it will output configuration logs during the device tree configuration process in the uboot stage.dtdebug must be configured before dtoverlay.

dtdebug=1

dtoverlay

Supports device tree overlays, providing a more flexible way to adjust the device tree.

[RDK X3] For example, to adjust the size of ION memory using ion_resize, the following configuration will modify the ION memory size to 1GB.

dtoverlay=ion_resize,size=0x40000000

[RDK X5] Use dtoverlay_spi5_spidev to add /dev/spidev5.0（Note: The CAN device has also received SPI5, so Spidev and CAN can only choose one from the other）

dtoverlay=dtoverlay_spi5_spidev

[Only X5 supports]ion

use ion_reserved_size、 ion_carveout_size 、ion_cma_size to modify the ION partition size.

boot name	dts name	dts compatible	size
ion_reserved_size	ion_reserved	ion-pool	320M
ion_carveout_size	ion_carveout	ion-carveout	320M
ion_cma_size	ion_cma	ion-cma	128M

ion=ion_reserved_size=0x14000000
ion=ion_carveout_size=0x14000000
ion=ion_cma_size=0x08000000

dtparam

Supports enabling and disabling buses such as uart, i2c, spi, i2s, etc.

Currently supported options:
[RDK X3]: uart3, spi0, spi1, spi2, i2c0, i2c1, i2c2, i2c3, i2c4, i2c5, i2s0, i2s1

[RDK X5]: uart1, uart2, uart3, uart6，spi1, spi2, i2c0, i2c1, i2c5, i2c4, i2c5, dw_i2s1

Note

The RDK X5 needs to pay attention to the pin multiplexing relationship. When all interfaces in a row are disabled, the pin functions as a GPIO pin.

Function 1	Function 2
uart3	i2c5
i2c0	pwm2
spi2	pwm0
spi2	pwm1
i2c1	pwm3

For example, to disable uart3:

dtparam=uart3=off

For example, to enable i2c5:

dtparam=i2c5=on

CPU Frequency

arm_boost

When set to 1, enables overclocking. For RDK v1.x, the maximum frequency is increased to 1.5GHz. For RDK V2.0 and RDK Module, the maximum frequency is increased to 1.8GHz. Use cat /sys/devices/system/cpu/cpufreq/scaling_boost_frequencies to retrieve the higher CPU frequencies enabled by boost.

By default, overclocking is disabled. Set arm_boost to 1 to enable, for example:

arm_boost=1

governor

The scheduling method for CPU frequency. Various options like conservative, ondemand, userspace, powersave, performance, and schedutil are available. Use cat /sys/devices/system/cpu/cpufreq/scaling_available_governors to get the available modes.

For example, setting the CPU to run in performance mode:

governor=performance

Refer to CPU Frequency Management for more information on CPU scheduling methods.

frequency

When governor is set to userspace, this option allows the CPU to run at a fixed frequency. Currently, common frequencies like 240000, 500000, 800000, 1000000, 1200000, 1500000, 1800000 can be set. Use cat /sys/devices/system/cpu/cpufreq/scaling_available_frequencies to get the list of available frequencies.

For example, setting the CPU to run at 1GHz:

governor=userspace
frequency=1000000

X5 CPU Frequency

For details about CPU scheduling methods, please refer to X5 CPU Frequency Management. If you plan to overclock, be sure to read the section on CPU Overclocking in the document to fully understand the risks and precautions.

This section only introduces the configuration method via config.txt and does not include content related to scheduling policies or the principles of overclocking.

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arm_boost

When set to 1, overclocking is enabled, increasing the maximum frequency of the RDK X5 to 1.8GHz. You can check which higher CPU frequencies are enabled after boosting by running:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_boost_frequencies

governor

The scheduling method for CPU frequency can be selected from conservative ondemand userspace powersave performance schedutil. The available modes can be obtained by running cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_governors.

For example, to set the CPU to run in performance mode:

governor=performance

frequency

When the governor is set to userspace, this option can be used to set the CPU to run at a fixed frequency. Currently, frequencies such as 300000 600000 1200000 1500000 can generally be set. The specific list of available frequencies can be obtained by running cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies.

For example, to set the CPU to run at a reduced frequency of 1.2GHz:

governor=userspace
frequency=1200000

IO Initialization

gpio

Supports configuring IO functionality, including multiplexing, input/output modes, high/low output levels, and pull-up/pull-down modes.

gpio:
ip - Input                             Set as input mode
op - Output                            Set as output mode
f0-f3 - Func0-Func3                    Set function multiplexing (f3 sets to IO mode, refer to the register manual for other functions)
dh - Driving high (for outputs)        Output high level
dl - Driving low (for outputs)         Output low level
pu - Pull up                           Enable pull-up
pd - Pull down                         Enable pull-down
pn/np - No pull                        No pull-up or pull-down

Example

Configure GPIO5 and GPIO6 on 40Pin as IO mode:

gpio=5=f3
gpio=6=f3
# For consecutive pins, you can also configure them in the following way
gpio=5-6=f3

Configure GPIO5 on 40Pin as input mode:

gpio=5=f3
gpio=5=ip

Configure GPIO6 on 40Pin as output mode and drive low level:

gpio=6=f3
gpio=6=op,dl

Configure GPIO6 on 40Pin as output mode, drive high level and set pull up:

gpio=6=f3
gpio=6=op,dl,pu

Temperature Control

throttling_temp

The temperature point at which the system CPU and BPU will throttle. When the temperature exceeds this point, the CPU and BPU will reduce their operating frequency to reduce power consumption. The CPU can go as low as 240MHz, while the BPU can go as low as 400MHz.

For example, set the downclock temperature to 86℃：

throttling_temp=86000

shutdown_temp

Shutdown temperature point of the system. If the temperature exceeds this point, the system will automatically shut down to protect the chip and hardware. It is recommended to perform heat dissipation treatment on the device to avoid system shutdown, as the device will not restart automatically after shutdown.

For example, set the shutdown temperature to 112℃：

shutdown_temp=112000

Option Filtering

Supports the use of [] to set filtering items. The filtering items need to be added at the end of the configuration file, because the part before the filtering item is considered 'all'. Once a filtering setting is added, the subsequent configurations belong to that filtering attribute until the end of the configuration file or another filtering item is set.

The supported filtering items are differentiated by hardware model, and the following filtering items are supported:

Filtering Item	Compatible Models
[all]	All hardware, default
[rdkv1]	RDK x3 v1.0, RDK x3 v1.1
[rdkv1.2]	RDK x3 v1.2
[rdkv2]	RDK x3 v2.1
[rdkmd]	RDK x3 Module
[x5-rdk]	RDK X5 V0.1

Voltage Domain

voltage_domain

Configures the voltage domain of the 40-pin, supporting configuration as 3.3V or 1.8V. If not configured, the default is 3.3V.

This configuration item needs to be used in conjunction with the jumper cap for voltage domain switching on the hardware.

Note

Only RDK Module supports this configuration.

For example, to configure the 40-pin of the RDK Module to work in 3v3 voltage mode, the following example uses [rdkmd] as the filtering item:

# Voltage domain configuration for 40 Pin, 3.3V or 1.8V, defualt 3.3V
# Only RDK Module supported
[rdkmd]
voltage_domain=3.3V