Kernel Linux Pin Control Subsystem

Sistemas embarcados com plataforma ARM geralmente não possuem barramentos com protocolos de auto configuração ou enumeração. Por essa causa, utilizam-se os Device Trees para configuração e descrição do hardware para o Kernel Linux. Uma função importante da configuração no hardware é a correta atribuição da pinagem e multiplexação da mesma para o funcionamento dos perifericos. Tal tarefa é atribuida aos device drivers de pin control do vendor do processador no kernel, que realizam o parse das configurações dos device trees e as atribuem nos registradores de GPIO. O objetivo da palestra é mostrar um overview sobre o Pin Control subsystem e como o kernel controla e gerencia as GPIOs do processador.

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1. KERNEL LINUX PIN CONTROL SUBSYSTEM matheus.bc@samsung.com
4. • GPIO - (Or the various ways to turn on a led in linux) • Overview • GPIO x Pin Control • GPIOLib Kernel Space • Legacy • Parse your device tree • New Descriptor-Based API • Device tree abstracted • GPIO in User Space • sysfs - Deprecated! (Why? This is so easy) • Char Device - Why not write a device driver? • Pin Control (I really need this?) • Pin Multiplexing • Pin Configuration • Generic Pin Mutiplexing and Configuration *Maker point of view
7. CASTELLO132 GPIO MUX OUT MUX IN PULL DOWN PULL UP
9. ATMEGA328P PB6 / PIN13 MUX OUT MUX IN PULL UP
11. ATMEGA328P PB6 / PIN13 MUX OUT MUX IN PULL UP
12. GPIO PINCTRL MUX INPUT / OUTPUT REQUEST READ / WRITE PIN STATES SET MUX ALTENATES FUNCTIONS SELECT PIN CONFIGURATIONS
13. GPIO PINCTRL MUX INPUT / OUTPUT REQUEST READ / WRITE PIN STATES SET MUX ALTENATES FUNCTIONS SELECT PIN CONFIGURATIONS
16. Applications (Aka Distro) GNU C Library (glibc) KERNEL Architecture-Dependent Kernel Code System Call Interface KERNEL SPACE USER SPACE
17. Applications (Aka Distro) GNU C Library (glibc) KERNEL Architecture-Dependent Kernel Code System Call Interface KERNEL SPACE USER SPACE ACCESS TO HARDWARE HAVE TO MADE IN KERNEL SPACE!
18. • Linus Walleij • PINCTRL Subsystem • Creator • Maintainer
30. This document is shared under the license: https://creativecommons.org/licenses/by-nc-sa/4.0
31. REFERENCES https://elinux.org/images/b/b6/Pin_Control_Subsystem_Overview.pdf https://dflund.se/~triad/papers/Linaro_pinctrl_overview.pdf https://elinux.org/images/9/9b/GPIO_for_Engineers_and_Makers.pdf