Documentation/arch/arm/pxa/mfp.rst

Source file repositories/reference/linux-study-clean/Documentation/arch/arm/pxa/mfp.rst

File Facts

System
Linux kernel
Corpus path
Documentation/arch/arm/pxa/mfp.rst
Extension
.rst
Size
10940 bytes
Lines
289
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

==============================================
MFP Configuration for PXA2xx/PXA3xx Processors
==============================================

			Eric Miao <eric.miao@marvell.com>

MFP stands for Multi-Function Pin, which is the pin-mux logic on PXA3xx and
later PXA series processors.  This document describes the existing MFP API,
and how board/platform driver authors could make use of it.

Basic Concept
=============

Unlike the GPIO alternate function settings on PXA25x and PXA27x, a new MFP
mechanism is introduced from PXA3xx to completely move the pin-mux functions
out of the GPIO controller. In addition to pin-mux configurations, the MFP
also controls the low power state, driving strength, pull-up/down and event
detection of each pin.  Below is a diagram of internal connections between
the MFP logic and the remaining SoC peripherals::

 +--------+
 |        |--(GPIO19)--+
 |  GPIO  |            |
 |        |--(GPIO...) |
 +--------+            |
                       |       +---------+
 +--------+            +------>|         |
 |  PWM2  |--(PWM_OUT)-------->|   MFP   |
 +--------+            +------>|         |-------> to external PAD
                       | +---->|         |
 +--------+            | | +-->|         |
 |  SSP2  |---(TXD)----+ | |   +---------+
 +--------+              | |
                         | |
 +--------+              | |
 | Keypad |--(MKOUT4)----+ |
 +--------+                |
                           |
 +--------+                |
 |  UART2 |---(TXD)--------+
 +--------+

NOTE: the external pad is named as MFP_PIN_GPIO19, it doesn't necessarily
mean it's dedicated for GPIO19, only as a hint that internally this pin
can be routed from GPIO19 of the GPIO controller.

To better understand the change from PXA25x/PXA27x GPIO alternate function
to this new MFP mechanism, here are several key points:

  1. GPIO controller on PXA3xx is now a dedicated controller, same as other
     internal controllers like PWM, SSP and UART, with 128 internal signals
     which can be routed to external through one or more MFPs (e.g. GPIO<0>
     can be routed through either MFP_PIN_GPIO0 as well as MFP_PIN_GPIO0_2,
     see arch/arm/mach-pxa/mfp-pxa300.h)

  2. Alternate function configuration is removed from this GPIO controller,
     the remaining functions are pure GPIO-specific, i.e.

       - GPIO signal level control
       - GPIO direction control
       - GPIO level change detection

  3. Low power state for each pin is now controlled by MFP, this means the
     PGSRx registers on PXA2xx are now useless on PXA3xx

  4. Wakeup detection is now controlled by MFP, PWER does not control the
     wakeup from GPIO(s) any more, depending on the sleeping state, ADxER
     (as defined in pxa3xx-regs.h) controls the wakeup from MFP

NOTE: with such a clear separation of MFP and GPIO, by GPIO<xx> we normally

Annotation

Implementation Notes