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Diffstat (limited to 'Documentation/blackfin/bfin-gpio-notes.txt')
-rw-r--r-- | Documentation/blackfin/bfin-gpio-notes.txt | 71 |
1 files changed, 0 insertions, 71 deletions
diff --git a/Documentation/blackfin/bfin-gpio-notes.txt b/Documentation/blackfin/bfin-gpio-notes.txt deleted file mode 100644 index d245f39c3d01..000000000000 --- a/Documentation/blackfin/bfin-gpio-notes.txt +++ /dev/null @@ -1,71 +0,0 @@ -/* - * File: Documentation/blackfin/bfin-gpio-notes.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 its 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 - interrupt. - 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. - - - |