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Documentation/platforms/arm/imxrt: added information regarding tickless mode support

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Signed-off-by: Michal Lenc <michallenc@seznam.cz>
This commit is contained in:
Michal Lenc
2021-07-12 18:35:46 +02:00
committed by Alan Carvalho de Assis
parent 28ad7b6376
commit cafcb0508f
2 changed files with 29 additions and 0 deletions
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Documentation/platforms/arm/imxrt/boards/teensy-4.x/index.rst
+14
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@@ -118,6 +118,20 @@ focused on network-related testing.
This configuration cannot be changed to Teensy 4.0 as this board does
not have Ethernet capability.
pikron-bb
---------
This is a configuration that compiles the NuttX for use with
open source/hardware `Base Board for Teensy 4.1
<https://gitlab.com/pikron/projects/imxrt-devel/-/wikis/teensy_bb>`_.
It includes CAN drivers, communication over serial port, Ethernet
support, support for 240 x 320 pixels LCD display and configuration
options for using NuttX with pysimCoder. NuttX also runs in
tickless mode with the resolution 10 usec.
This configuration cannot be changed to Teensy 4.0 as base board
is not designed for that.
pwm-4.1
-------
Documentation/platforms/arm/imxrt/index.rst
+15
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@@ -33,6 +33,21 @@ set as write-through but can be changed to write-back via Kconfig. While write-b
performance than write-through, it is not supported for all peripherals in NuttX yet. Write-back data
cache can not be selected while running Ethernet or serial port over USB.
Tickless OS
===========
With Tickless OS, the periodic, timer interrupt is eliminated and replaced with a one-shot,
interval timer, that becomes event driven instead of polled. This allows to run the MCU with
higher resolution without using more of the CPU bandwidth processing useless interrupts.
Only tickless via an alarm is currently supported for i.MX RT MCU, which can be selected by
CONFIG_SCHED_TICKLESS_ALARM option. CONFIG_USEC_PER_TICK option determines the resolution
of time reported by :c:func:`clock_systime_ticks()` and the resolution of times that can be set
for certain delays including watchdog timers and delayed work. It is important that value set in
CONFIG_USEC_PER_TICK represents the frequency of GPT timer that runs the tickless mode. Clock
source of the timer is 16.6 MHz, which is then devided by the prescaler value from 1 to 4096.
Possible values for CONFIG_USEC_PER_TICK are 10 or 100 for example.
Peripheral Support
==================