Texas Instruments AM335 Series Design Manual page 12

Linux Power Optimization Features
There are two options for loading the CM3 firmware: through the file system or by including it in the Kernel
itself. If using the Processor SDK, the firmware is included in /lib/firmware and the root filesystem should
handle loading it automatically. Placing any version of
to load automatically during boot. However, due to changes in the upstream kernel it is now required that
CONFIG_FW_LOADER_USER_HELPER_FALLBACK be enabled if the CONFIG_WKUP_M3_IPC is
being built-in to the kernel so that the firmware can be loaded once userspace and the root filesystem
becomes avaiable. The kernel configuration should be as follows, and enables not only the runtime
loading of CM3 firmware, but also suspend and resume:
CM3 Firmware Runtime Load Configuration
# Firmware Loading from rootfs
CONFIG_FW_LOADER_USER_HELPER=y
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
# AMx3 Power Config Options
CONFIG_MAILBOX=y
CONFIG_OMAP2PLUS_MBOX=y
CONFIG_WKUP_M3_RPROC=y
CONFIG_SOC_TI=y
CONFIG_WKUP_M3_IPC=y
CONFIG_TI_EMIF_SRAM=y
CONFIG_AMX3_PM=y
CONFIG_RTC_DRV_OMAP=y
Another option is to bake the CM3 firmware directly into the kernel. Using make menuconfig,
select
Device Drivers ---> Generic Driver
In this menu, find the following section and add the appropriate firmware name and directory:
...
-*- Userspace firmware loading support
[*] Include in-kernel firmware blobs in the kernel binary
(am335x-pm-firmware.elf) External firmware blobs to build into the kernel binary
(firmware) Firmware blobs root directory
During the boot process, if the CM3 firmware was properly loaded, you will see the following message:
CM3 Firmware Load Successful
wkup_m3_ipc 44e11324.wkup_m3_ipc: CM3 Firmware Version = 0x191
wkup_m3_rproc Driver
This driver is responsible for loading and booting the CM3 firmware on the wkup_m3 inside the SoC using
the remoteproc framework.
Source Location:
The source code for this driver can be found in:
drivers/remoteproc/wkup_m3_rproc.c
wkup_m3_ipc Driver
This driver exposes an API to be used by the PM code to provide board and SoC specific data from the
kernel to the CM3 firmware, request certain power state transitions, and query the status of any previous
power state transitions performed by the CM3 firmware.
Source Location:
The source code for this driver can be found in:
drivers/soc/ti/wkup_m3_ipc.c
12
AM335x Low Power Design Guide
am335x-pm-firmware.elf
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SPRAC74A – February 2017 – Revised March 2017
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