2.5 Commercial release configurations
Some features are intended for use only during the development and debugging stages. These features must be
disabled prior to commercial release to improve performance and user experience.
Disabling kernel debug feature to optimize HLOS performance
By default, the kernel configuration file includes many settings that are useful during the development and
debugging phase but may affect performance.
To disable the default kernel debugging settings, use LINUX/android/kernel/arch/arm/configs/msm8226-
perf_defconfig instead of msm8226_defconfig.
Enabling Subsystem Restart (SSR)
When a subsystem (mode, wifi, video core, etc.) crashes, the subsystem can be configured to automatically notify
the AP. The AP then restarts the applicable subsystem. This provides a better user experience.
1. To enable subsystem restart prior to commercial release, open the
android/device/qcom/msmXXXX/system.prop file.
2. Modify the persist.sys.ssr.restart_level property as follows:
persist.sys.ssr.restart_level=modem,wcnss,adsp,venus or 1
This enables subsystem restart for modem, wifi, adsp, and video subsystems. This is the recommended setting
for commercial release.
During engineering development, this property should be set to 1 as shown below. This enables subsystem panic
which is useful for engineering releases.
persist.sys.ssr.restart_level=1
Subsystem panic means that when each subsystem encounters a problem which triggers a reset, the AP will catch
this event and will call kernel panic. As a result, the device can enter download mode to capture ramdump.
Disabling Download Mode
During development and debugging, Download mode is used to get memory dump for crash analysis. For a
production device, Download mode is not needed since the device should just reboot.
80-NP616-2 A
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Confidential and Proprietary – Qualcomm Technologies, Inc.
MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATIONSoftware Customization Guidelines
Use one of the following methods to disable download mode:

Modify the arch/arm/mach-msm/restart.c file as follows:
static int download_mode = 1;
change 1 -> 0
Modifying the download_mode value is the preferred method because you have the ability to dynamically
obtain a memory dump for a launched phone. Download mode can be enabled from the shell:
echo 1 > /sys/module/restart/parameters/download_mode

Remove CONFIG_MSM_DLOAD_MODE=y from
LINUX/android/kernel/arch/arm/configs/msm8226_defconfig
Using this method, Download mode is completely disabled. It cannot be enabled dynamically so you will not
be able to switch to Download mode for image programming.
If needed, Firehose can be used for image programming. QFIL (QPST 2.7 Build 416 or later) supports Firehose.
QFIL uses adb reboot edl to switch to emergency download mode.