[media] exynos4-is: Add FIMC-IS ISP I2C bus driver

This patch adds the ISP I2C bus controller driver files.
Creating a standard I2C bus adapter, even if the driver doesn't
actually communicate with the hardware and it is instead
controlled by the ISP firmware running on the Cortex-A5, allows
to use standard hardware description in the device tree. As the
sensor would have actually had a standard V4L2 sub-device driver
run on the host CPU.
This approach allows to adapt the driver with a relatively small
effort should the Imaging Subsystem architecture change so that
the I2C bus is handled by the host's CPU OS, rather than the
internal FIMC-IS ARM CPU firmware. The image sensor driver could
be a standard I2C client driver, as in case of most existing
image sensors.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/exynos4-is/fimc-is-i2c.c

+/*
+ * Samsung EXYNOS4x12 FIMC-IS (Imaging Subsystem) driver
+ *
+ * Copyright (C) 2013 Samsung Electronics Co., Ltd.
+ *
+ * Author: Sylwester Nawrocki <s.nawrocki@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/of_i2c.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include "fimc-is-i2c.h"
+
+struct fimc_is_i2c {
+	struct i2c_adapter adapter;
+	struct clk *clock;
+};
+
+/*
+ * An empty algorithm is used as the actual I2C bus controller driver
+ * is implemented in the FIMC-IS subsystem firmware and the host CPU
+ * doesn't access the I2C bus controller.
+ */
+static const struct i2c_algorithm fimc_is_i2c_algorithm;
+
+static int fimc_is_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct fimc_is_i2c *isp_i2c;
+	struct i2c_adapter *i2c_adap;
+	int ret;
+
+	isp_i2c = devm_kzalloc(&pdev->dev, sizeof(*isp_i2c), GFP_KERNEL);
+	if (!isp_i2c)
+		return -ENOMEM;
+
+	isp_i2c->clock = devm_clk_get(&pdev->dev, "i2c_isp");
+	if (IS_ERR(isp_i2c->clock)) {
+		dev_err(&pdev->dev, "failed to get the clock\n");
+		return PTR_ERR(isp_i2c->clock);
+	}
+
+	i2c_adap = &isp_i2c->adapter;
+	i2c_adap->dev.of_node = node;
+	i2c_adap->dev.parent = &pdev->dev;
+	strlcpy(i2c_adap->name, "exynos4x12-isp-i2c", sizeof(i2c_adap->name));
+	i2c_adap->owner = THIS_MODULE;
+	i2c_adap->algo = &fimc_is_i2c_algorithm;
+	i2c_adap->class = I2C_CLASS_SPD;
+
+	ret = i2c_add_adapter(i2c_adap);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to add I2C bus %s\n",
+						node->full_name);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, isp_i2c);
+
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_enable(&i2c_adap->dev);
+
+	of_i2c_register_devices(i2c_adap);
+
+	return 0;
+}
+
+static int fimc_is_i2c_remove(struct platform_device *pdev)
+{
+	struct fimc_is_i2c *isp_i2c = platform_get_drvdata(pdev);
+
+	pm_runtime_disable(&isp_i2c->adapter.dev);
+	pm_runtime_disable(&pdev->dev);
+	i2c_del_adapter(&isp_i2c->adapter);
+
+	return 0;
+}
+
+static int fimc_is_i2c_suspend(struct device *dev)
+{
+	struct fimc_is_i2c *isp_i2c = dev_get_drvdata(dev);
+	clk_disable_unprepare(isp_i2c->clock);
+	return 0;
+}
+
+static int fimc_is_i2c_resume(struct device *dev)
+{
+	struct fimc_is_i2c *isp_i2c = dev_get_drvdata(dev);
+	return clk_prepare_enable(isp_i2c->clock);
+}
+
+UNIVERSAL_DEV_PM_OPS(fimc_is_i2c_pm_ops, fimc_is_i2c_suspend,
+		     fimc_is_i2c_resume, NULL);
+
+static const struct of_device_id fimc_is_i2c_of_match[] = {
+	{ .compatible = FIMC_IS_I2C_COMPATIBLE },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, fimc_is_i2c_of_match);
+
+static struct platform_driver fimc_is_i2c_driver = {
+	.probe		= fimc_is_i2c_probe,
+	.remove		= fimc_is_i2c_remove,
+	.driver = {
+		.of_match_table = fimc_is_i2c_of_match,
+		.name		= "fimc-isp-i2c",
+		.owner		= THIS_MODULE,
+		.pm		= &fimc_is_i2c_pm_ops,
+	}
+};
+
+int fimc_is_register_i2c_driver(void)
+{
+	return platform_driver_register(&fimc_is_i2c_driver);
+}
+EXPORT_SYMBOL(fimc_is_register_i2c_driver);
+
+void fimc_is_unregister_i2c_driver(void)
+{
+	platform_driver_unregister(&fimc_is_i2c_driver);
+}
+EXPORT_SYMBOL(fimc_is_unregister_i2c_driver);

drivers/media/platform/exynos4-is/fimc-is-i2c.h

+/*
+ * Samsung EXYNOS4x12 FIMC-IS (Imaging Subsystem) driver
+ *
+ * Copyright (C) 2013 Samsung Electronics Co., Ltd.
+ * Sylwester Nawrocki <s.nawrocki@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define FIMC_IS_I2C_COMPATIBLE	"samsung,exynos4212-i2c-isp"
+
+int fimc_is_register_i2c_driver(void);
+void fimc_is_unregister_i2c_driver(void);