summaryrefslogtreecommitdiffstats
path: root/kernel/include/linux/spi/spi_gpio.h
diff options
context:
space:
mode:
authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/include/linux/spi/spi_gpio.h
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/include/linux/spi/spi_gpio.h')
-rw-r--r--kernel/include/linux/spi/spi_gpio.h71
1 files changed, 71 insertions, 0 deletions
diff --git a/kernel/include/linux/spi/spi_gpio.h b/kernel/include/linux/spi/spi_gpio.h
new file mode 100644
index 000000000..1634ce31c
--- /dev/null
+++ b/kernel/include/linux/spi/spi_gpio.h
@@ -0,0 +1,71 @@
+#ifndef __LINUX_SPI_GPIO_H
+#define __LINUX_SPI_GPIO_H
+
+/*
+ * For each bitbanged SPI bus, set up a platform_device node with:
+ * - name "spi_gpio"
+ * - id the same as the SPI bus number it implements
+ * - dev.platform data pointing to a struct spi_gpio_platform_data
+ *
+ * Or, see the driver code for information about speedups that are
+ * possible on platforms that support inlined access for GPIOs (no
+ * spi_gpio_platform_data is used).
+ *
+ * Use spi_board_info with these busses in the usual way, being sure
+ * that the controller_data being the GPIO used for each device's
+ * chipselect:
+ *
+ * static struct spi_board_info ... [] = {
+ * ...
+ * // this slave uses GPIO 42 for its chipselect
+ * .controller_data = (void *) 42,
+ * ...
+ * // this one uses GPIO 86 for its chipselect
+ * .controller_data = (void *) 86,
+ * ...
+ * };
+ *
+ * If chipselect is not used (there's only one device on the bus), assign
+ * SPI_GPIO_NO_CHIPSELECT to the controller_data:
+ * .controller_data = (void *) SPI_GPIO_NO_CHIPSELECT;
+ *
+ * If the MISO or MOSI pin is not available then it should be set to
+ * SPI_GPIO_NO_MISO or SPI_GPIO_NO_MOSI.
+ *
+ * If the bitbanged bus is later switched to a "native" controller,
+ * that platform_device and controller_data should be removed.
+ */
+
+#define SPI_GPIO_NO_CHIPSELECT ((unsigned long)-1l)
+#define SPI_GPIO_NO_MISO ((unsigned long)-1l)
+#define SPI_GPIO_NO_MOSI ((unsigned long)-1l)
+
+/**
+ * struct spi_gpio_platform_data - parameter for bitbanged SPI master
+ * @sck: number of the GPIO used for clock output
+ * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
+ * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
+ * @num_chipselect: how many slaves to allow
+ *
+ * All GPIO signals used with the SPI bus managed through this driver
+ * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
+ * of some alternate function.
+ *
+ * It can be convenient to use this driver with pins that have alternate
+ * functions associated with a "native" SPI controller if a driver for that
+ * controller is not available, or is missing important functionality.
+ *
+ * On platforms which can do so, configure MISO with a weak pullup unless
+ * there's an external pullup on that signal. That saves power by avoiding
+ * floating signals. (A weak pulldown would save power too, but many
+ * drivers expect to see all-ones data as the no slave "response".)
+ */
+struct spi_gpio_platform_data {
+ unsigned sck;
+ unsigned long mosi;
+ unsigned long miso;
+
+ u16 num_chipselect;
+};
+
+#endif /* __LINUX_SPI_GPIO_H */