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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /Documentation/blackfin
Initial import
Diffstat (limited to 'Documentation/blackfin')
-rw-r--r--Documentation/blackfin/00-INDEX10
-rw-r--r--Documentation/blackfin/Makefile5
-rw-r--r--Documentation/blackfin/bfin-gpio-notes.txt71
-rw-r--r--Documentation/blackfin/bfin-spi-notes.txt16
-rw-r--r--Documentation/blackfin/gptimers-example.c83
5 files changed, 185 insertions, 0 deletions
diff --git a/Documentation/blackfin/00-INDEX b/Documentation/blackfin/00-INDEX
new file mode 100644
index 000000000..c54fcdd4a
--- /dev/null
+++ b/Documentation/blackfin/00-INDEX
@@ -0,0 +1,10 @@
+00-INDEX
+ - This file
+Makefile
+ - Makefile for gptimers example file.
+bfin-gpio-notes.txt
+ - Notes in developing/using bfin-gpio driver.
+bfin-spi-notes.txt
+ - Notes for using bfin spi bus driver.
+gptimers-example.c
+ - gptimers example
diff --git a/Documentation/blackfin/Makefile b/Documentation/blackfin/Makefile
new file mode 100644
index 000000000..6782c58fb
--- /dev/null
+++ b/Documentation/blackfin/Makefile
@@ -0,0 +1,5 @@
+ifneq ($(CONFIG_BLACKFIN),)
+ifneq ($(CONFIG_BFIN_GPTIMERS),)
+obj-m := gptimers-example.o
+endif
+endif
diff --git a/Documentation/blackfin/bfin-gpio-notes.txt b/Documentation/blackfin/bfin-gpio-notes.txt
new file mode 100644
index 000000000..d245f39c3
--- /dev/null
+++ b/Documentation/blackfin/bfin-gpio-notes.txt
@@ -0,0 +1,71 @@
+/*
+ * 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.
+
+
+
diff --git a/Documentation/blackfin/bfin-spi-notes.txt b/Documentation/blackfin/bfin-spi-notes.txt
new file mode 100644
index 000000000..eae6eaf2a
--- /dev/null
+++ b/Documentation/blackfin/bfin-spi-notes.txt
@@ -0,0 +1,16 @@
+SPI Chip Select behavior:
+
+With the Blackfin on-chip SPI peripheral, there is some logic tied to the CPHA
+bit whether the Slave Select Line is controlled by hardware (CPHA=0) or
+controlled by software (CPHA=1). However, the Linux SPI bus driver assumes that
+the Slave Select is always under software control and being asserted during
+the entire SPI transfer. - And not just bits_per_word duration.
+
+In most cases you can utilize SPI MODE_3 instead of MODE_0 to work-around this
+behavior. If your SPI slave device in question requires SPI MODE_0 or MODE_2
+timing, you can utilize the GPIO controlled SPI Slave Select option instead.
+In this case, you should use GPIO based CS for all of your slaves and not just
+the ones using mode 0 or 2 in order to guarantee correct CS toggling behavior.
+
+You can even use the same pin whose peripheral role is a SSEL,
+but use it as a GPIO instead.
diff --git a/Documentation/blackfin/gptimers-example.c b/Documentation/blackfin/gptimers-example.c
new file mode 100644
index 000000000..b1bd6340e
--- /dev/null
+++ b/Documentation/blackfin/gptimers-example.c
@@ -0,0 +1,83 @@
+/*
+ * Simple gptimers example
+ * http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:gptimers
+ *
+ * Copyright 2007-2009 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/module.h>
+
+#include <asm/gptimers.h>
+#include <asm/portmux.h>
+
+/* ... random driver includes ... */
+
+#define DRIVER_NAME "gptimer_example"
+
+struct gptimer_data {
+ uint32_t period, width;
+};
+static struct gptimer_data data;
+
+/* ... random driver state ... */
+
+static irqreturn_t gptimer_example_irq(int irq, void *dev_id)
+{
+ struct gptimer_data *data = dev_id;
+
+ /* make sure it was our timer which caused the interrupt */
+ if (!get_gptimer_intr(TIMER5_id))
+ return IRQ_NONE;
+
+ /* read the width/period values that were captured for the waveform */
+ data->width = get_gptimer_pwidth(TIMER5_id);
+ data->period = get_gptimer_period(TIMER5_id);
+
+ /* acknowledge the interrupt */
+ clear_gptimer_intr(TIMER5_id);
+
+ /* tell the upper layers we took care of things */
+ return IRQ_HANDLED;
+}
+
+/* ... random driver code ... */
+
+static int __init gptimer_example_init(void)
+{
+ int ret;
+
+ /* grab the peripheral pins */
+ ret = peripheral_request(P_TMR5, DRIVER_NAME);
+ if (ret) {
+ printk(KERN_NOTICE DRIVER_NAME ": peripheral request failed\n");
+ return ret;
+ }
+
+ /* grab the IRQ for the timer */
+ ret = request_irq(IRQ_TIMER5, gptimer_example_irq, IRQF_SHARED, DRIVER_NAME, &data);
+ if (ret) {
+ printk(KERN_NOTICE DRIVER_NAME ": IRQ request failed\n");
+ peripheral_free(P_TMR5);
+ return ret;
+ }
+
+ /* setup the timer and enable it */
+ set_gptimer_config(TIMER5_id, WDTH_CAP | PULSE_HI | PERIOD_CNT | IRQ_ENA);
+ enable_gptimers(TIMER5bit);
+
+ return 0;
+}
+module_init(gptimer_example_init);
+
+static void __exit gptimer_example_exit(void)
+{
+ disable_gptimers(TIMER5bit);
+ free_irq(IRQ_TIMER5, &data);
+ peripheral_free(P_TMR5);
+}
+module_exit(gptimer_example_exit);
+
+MODULE_LICENSE("BSD");