Bureaucrats, dave_user, Administrators
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|-
|1.0.0
|November 2016January 2017
|First public release
|}
[[File:SoloX-AMP.png|thumb|center|600px400px|Simplified block diagram of the AMP configuration]]
*GPT (General Purpose Timer), including associated I/Os
*some additional GPIOs.
It is also required that :*M4 firmware is booted before the Linux kernel and that the [2]*The Linux kernel has exclusive control of some other GPIOSGPIOs.
Satisfying the first requirement has been the trickiest challenge because, by default, U-Boot and Linux kernel make use of GPT timer, as per official BSP released by NXP. This is not a big deal for U-Boot, because it just uses this timer to handle timeouts and to measure time intervals. The things are more complicated with regard to the Linux kernel, because GPT is used as kernel's clock source. As such, it is involved in the scheduling process and it is dynamically reconfigured over the time, depending on power saving policies.
To solve this issue, both U-Boot and Linux kernel have been modified, in order to use EPIT timer instead. In spite of this modification, we have been able to preserve Linux's power saving mechanisms.
In order to protect the peripherals that have to be under the exclusive control of the M4 core, RDC has been configured accordingly. For example, the memory area in which GPT registers are mapped, is accessible by the M4 core only. RDC initialization is performed by M4 itself. It is worth remembering that the its granularity is an important factor that has to be taken in consideration. In this application, for example, it has had to choose different GPIO banks for M4 and A9. In case the same bank was chosen, it would have been impossible to partition GPIOs across the two cores, because some resources are shared among all of the GPIOs belonging to the same bank (for example the clocks feeding the functional blockGPIO module). For this reason, two different banks have been chosen.
#A9 core
#*comes out of reset
#*starts Linux kernel on Cortex-A9 core.
#once Linux kernel has completed the bootstrap process, a user space application establishes a communication channel with M4 core, through [https://www.kernel.org/doc/Documentation/remoteproc.txt RPMsg].