[PATCH linux v4 13/20] fsi: Add GPIO master driver

[christopher.lee.bostic at gmail.com]

From: Jeremy Kerr <jk at ozlabs.org>

Signed-off-by: Jeremy Kerr <jk at ozlabs.org>
---
 .../devicetree/bindings/fsi/fsi-master-gpio.txt    |  8 ++
 drivers/fsi/Kconfig                                |  7 ++
 drivers/fsi/Makefile                               |  1 +
 drivers/fsi/fsi-master-gpio.c                      | 92 ++++++++++++++++++++++
 4 files changed, 108 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt
 create mode 100644 drivers/fsi/fsi-master-gpio.c

diff --git a/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt b/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt
new file mode 100644
index 0000000..44762a3
--- /dev/null
+++ b/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt
@@ -0,0 +1,8 @@
+Device-tree bindings for gpio-based FSI master driver
+-----------------------------------------------------
+
+fsi-master {
+	compatible = "ibm,fsi-master", "ibm,fsi-master-gpio";
+	clk-gpio = <&gpio 0>;
+	data-gpio = <&gpio 1>;
+}
diff --git a/drivers/fsi/Kconfig b/drivers/fsi/Kconfig
index f065dbe..69e7ee8 100644
--- a/drivers/fsi/Kconfig
+++ b/drivers/fsi/Kconfig
@@ -17,6 +17,13 @@ config FSI_MASTER_FAKE
 	depends on FSI
 	---help---
 	This option enables a fake FSI master driver for debugging.
+
+config FSI_MASTER_GPIO
+	tristate "GPIO-based FSI master"
+	depends on FSI
+	select GPIO_DEVRES
+	---help---
+	This option enables a FSI master driver, using GPIO lines directly.
 endif
 
 endmenu
diff --git a/drivers/fsi/Makefile b/drivers/fsi/Makefile
index 847c00c..2021ce5 100644
--- a/drivers/fsi/Makefile
+++ b/drivers/fsi/Makefile
@@ -1,3 +1,4 @@
 
 obj-$(CONFIG_FSI) += fsi-core.o
 obj-$(CONFIG_FSI_MASTER_FAKE) += fsi-master-fake.o
+obj-$(CONFIG_FSI_MASTER_GPIO) += fsi-master-gpio.o
diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
new file mode 100644
index 0000000..3855829
--- /dev/null
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -0,0 +1,92 @@
+/*
+ * A FSI master controller, using a simple GPIO bit-banging interface
+ */
+
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+
+#include "fsi-master.h"
+
+struct fsi_master_gpio {
+	struct fsi_master	master;
+	struct gpio_desc	*gpio_clk;
+	struct gpio_desc	*gpio_data;
+};
+
+#define to_fsi_master_gpio(m) container_of(m, struct fsi_master_gpio, master)
+
+struct fsi_gpio_msg {
+	uint64_t	msg;
+	uint8_t		bits;
+};
+
+static int fsi_master_gpio_read(struct fsi_master *_master, int link,
+		uint8_t slave, uint32_t addr, void *val, size_t size)
+{
+	struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+
+	if (link != 0)
+		return -ENODEV;
+
+	/* todo: format read into a message, send, poll for response */
+	(void)master;
+
+
+	return 0;
+}
+
+static int fsi_master_gpio_write(struct fsi_master *_master, int link,
+		uint8_t slave, uint32_t addr, const void *val, size_t size)
+{
+	struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+
+	if (link != 0)
+		return -ENODEV;
+
+	/* todo: format write into a message, send, poll for response */
+	(void)master;
+
+	return 0;
+}
+
+static int fsi_master_gpio_probe(struct platform_device *pdev)
+{
+	struct fsi_master_gpio *master;
+	struct gpio_desc *gpio;
+
+	master = devm_kzalloc(&pdev->dev, sizeof(*master), GFP_KERNEL);
+	if (!master)
+		return -ENOMEM;
+
+	gpio = devm_gpiod_get(&pdev->dev, "clk", 0);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+	master->gpio_clk = gpio;
+
+	gpio = devm_gpiod_get(&pdev->dev, "data", 0);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+	master->gpio_data = gpio;
+
+	master->master.read = fsi_master_gpio_read;
+	master->master.write = fsi_master_gpio_write;
+
+	return fsi_master_register(&master->master);
+}
+
+static const struct of_device_id fsi_master_gpio_match[] = {
+	{ .compatible = "ibm,fsi-master-gpio" },
+	{ },
+};
+
+static struct platform_driver fsi_master_gpio_driver = {
+	.driver = {
+		.name		= "fsi-master-gpio",
+		.of_match_table	= fsi_master_gpio_match,
+	},
+	.probe	= fsi_master_gpio_probe,
+};
+
+module_platform_driver(fsi_master_gpio_driver);
+
-- 
1.8.2.2