mirror of
https://github.com/adulau/aha.git
synced 2024-12-30 20:56:23 +00:00
72 lines
2.4 KiB
Text
72 lines
2.4 KiB
Text
|
/*
|
||
|
|
* File: Documentation/blackfin/bfin-gpio-note.txt
|
||
|
|
* Based on:
|
||
|
|
* Author:
|
||
|
|
*
|
||
|
|
* Created: $Id: bfin-gpio-note.txt 2008-11-24 16:42 grafyang $
|
||
|
|
* Description: This file contains the notes in developing/using bfin-gpio.
|
||
|
|
*
|
||
|
|
*
|
||
|
|
* Rev:
|
||
|
|
*
|
||
|
|
* Modified:
|
||
|
|
* Copyright 2004-2008 Analog Devices Inc.
|
||
|
|
*
|
||
|
|
* Bugs: Enter bugs at http://blackfin.uclinux.org/
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
|
||
|
|
|
||
|
|
1. Blackfin GPIO introduction
|
||
|
|
|
||
|
|
There are many GPIO pins on Blackfin. Most of these pins are muxed to
|
||
|
|
multi-functions. They can be configured as peripheral, or just as GPIO,
|
||
|
|
configured to input with interrupt enabled, or output.
|
||
|
|
|
||
|
|
For detailed information, please see "arch/blackfin/kernel/bfin_gpio.c",
|
||
|
|
or the relevant HRM.
|
||
|
|
|
||
|
|
|
||
|
|
2. Avoiding resource conflict
|
||
|
|
|
||
|
|
Followed function groups are used to avoiding resource conflict,
|
||
|
|
- Use the pin as peripheral,
|
||
|
|
int peripheral_request(unsigned short per, const char *label);
|
||
|
|
int peripheral_request_list(const unsigned short per[], const char *label);
|
||
|
|
void peripheral_free(unsigned short per);
|
||
|
|
void peripheral_free_list(const unsigned short per[]);
|
||
|
|
- Use the pin as GPIO,
|
||
|
|
int bfin_gpio_request(unsigned gpio, const char *label);
|
||
|
|
void bfin_gpio_free(unsigned gpio);
|
||
|
|
- Use the pin as GPIO interrupt,
|
||
|
|
int bfin_gpio_irq_request(unsigned gpio, const char *label);
|
||
|
|
void bfin_gpio_irq_free(unsigned gpio);
|
||
|
|
|
||
|
|
The request functions will record the function state for a certain pin,
|
||
|
|
the free functions will clear it's function state.
|
||
|
|
Once a pin is requested, it can't be requested again before it is freed by
|
||
|
|
previous caller, otherwise kernel will dump stacks, and the request
|
||
|
|
function fail.
|
||
|
|
These functions are wrapped by other functions, most of the users need not
|
||
|
|
care.
|
||
|
|
|
||
|
|
|
||
|
|
3. But there are some exceptions
|
||
|
|
- Kernel permit the identical GPIO be requested both as GPIO and GPIO
|
||
|
|
interrut.
|
||
|
|
Some drivers, like gpio-keys, need this behavior. Kernel only print out
|
||
|
|
warning messages like,
|
||
|
|
bfin-gpio: GPIO 24 is already reserved by gpio-keys: BTN0, and you are
|
||
|
|
configuring it as IRQ!
|
||
|
|
|
||
|
|
Note: Consider the case that, if there are two drivers need the
|
||
|
|
identical GPIO, one of them use it as GPIO, the other use it as
|
||
|
|
GPIO interrupt. This will really cause resource conflict. So if
|
||
|
|
there is any abnormal driver behavior, please check the bfin-gpio
|
||
|
|
warning messages.
|
||
|
|
|
||
|
|
- Kernel permit the identical GPIO be requested from the same driver twice.
|
||
|
|
|
||
|
|
|
||
|
|
|