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* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/blackfin-2.6: (171 commits)
  Blackfin arch: fix bug - BF527 0.2 silicon has different CPUID (DSPID) value
  Blackfin arch: Enlarge flash partition for kenel for bf533/bf537 boards
  Blackfin arch: fix bug: kernel crash when enable SDIO host driver
  Blackfin arch: Print FP at level KERN_NOTICE
  Blackfin arch: drop ad73311 test code
  Blackfin arch: update board default configs
  Blackfin arch: Set PB4 as the default irq for bf548 board v1.4+.
  Blackfin arch: fix typo in early printk bit size processing
  Blackfin arch: enable reprogram cclk and sclk for bf518f-ezbrd
  Blackfin arch: add SDIO host driver platform data
  Blackfin arch: fix bug - kernel stops at initial console
  Blackfin arch: fix bug - kernel crash after config IP for ethernet port
  Blackfin arch: add sdh support for bf518f-ezbrd
  Blackfin arch: fix bug - kernel detects BF532 incorrectly
  Blackfin arch: add () to avoid warnings from gcc
  Blackfin arch: change HWTRACE Kconfig and set it on default
  Blackfin arch: Clean oprofile build path for blackfin
  Blackfin arch: remove hardware PM code, oprofile not use it
  Blackfin arch: rewrite get_sclk()/get_vco()
  Blackfin arch: cleanup and unify the ins functions
  ...
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Linus Torvalds committed Jan 7, 2009
2 parents 2f2408a + 06af15e commit 5bb47b9
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3 changes: 3 additions & 0 deletions Documentation/blackfin/00-INDEX
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Expand Up @@ -9,3 +9,6 @@ cachefeatures.txt

Filesystems
- Requirements for mounting the root file system.

bfin-gpio-note.txt
- Notes in developing/using bfin-gpio driver.
71 changes: 71 additions & 0 deletions Documentation/blackfin/bfin-gpio-notes.txt
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@@ -0,0 +1,71 @@
/*
* 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.



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