drivers: bus: add a new driver for WEIM

The WEIM(Wireless External Interface Module) works like a bus.
You can attach many different devices on it, such as NOR, onenand.

In the case of i.MX6q-sabreauto, the NOR is connected to WEIM.

This patch also adds the devicetree binding document.
The driver only works when the devicetree is enabled.

Signed-off-by: Huang Shijie <[e-mail]>
Acked-by: Sascha Hauer <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

Documentation/devicetree/bindings/bus/imx-weim.txt

···
+Device tree bindings for i.MX Wireless External Interface Module (WEIM)
+
+The term "wireless" does not imply that the WEIM is literally an interface
+without wires. It simply means that this module was originally designed for
+wireless and mobile applications that use low-power technology.
+
+The actual devices are instantiated from the child nodes of a WEIM node.
+
+Required properties:
+
+ - compatible:		Should be set to "fsl,imx6q-weim"
+ - reg:			A resource specifier for the register space
+			(see the example below)
+ - clocks:		the clock, see the example below.
+ - #address-cells:	Must be set to 2 to allow memory address translation
+ - #size-cells:		Must be set to 1 to allow CS address passing
+ - ranges:		Must be set up to reflect the memory layout with four
+			integer values for each chip-select line in use:
+
+			   <cs-number> 0 <physical address of mapping> <size>
+
+Timing property for child nodes. It is mandatory, not optional.
+
+ - fsl,weim-cs-timing:	The timing array, contains 6 timing values for the
+			child node. We can get the CS index from the child
+			node's "reg" property. This property contains the values
+			for the registers EIM_CSnGCR1, EIM_CSnGCR2, EIM_CSnRCR1,
+			EIM_CSnRCR2, EIM_CSnWCR1, EIM_CSnWCR2 in this order.
+
+Example for an imx6q-sabreauto board, the NOR flash connected to the WEIM:
+
+	weim: weim@021b8000 {
+		compatible = "fsl,imx6q-weim";
+		reg = <0x021b8000 0x4000>;
+		clocks = <&clks 196>;
+		#address-cells = <2>;
+		#size-cells = <1>;
+		ranges = <0 0 0x08000000 0x08000000>;
+
+		nor@0,0 {
+			compatible = "cfi-flash";
+			reg = <0 0 0x02000000>;
+			#address-cells = <1>;
+			#size-cells = <1>;
+			bank-width = <2>;
+			fsl,weim-cs-timing = <0x00620081 0x00000001 0x1c022000
+					0x0000c000 0x1404a38e 0x00000000>;
+		};
+	};

drivers/bus/Kconfig

···
 
 menu "Bus devices"
 
+config IMX_WEIM
+	bool "Freescale EIM DRIVER"
+	depends on ARCH_MXC
+	help
+	  Driver for i.MX6 WEIM controller.
+	  The WEIM(Wireless External Interface Module) works like a bus.
+	  You can attach many different devices on it, such as NOR, onenand.
+	  But now, we only support the Parallel NOR.
+
 config MVEBU_MBUS
 	bool
 	depends on PLAT_ORION

drivers/bus/Makefile

···
 # Makefile for the bus drivers.
 #
 
+obj-$(CONFIG_IMX_WEIM)	+= imx-weim.o
 obj-$(CONFIG_MVEBU_MBUS) += mvebu-mbus.o
 obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
 

drivers/bus/imx-weim.c

···
+/*
+ * EIM driver for Freescale's i.MX chips
+ *
+ * Copyright (C) 2013 Freescale Semiconductor, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/module.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/of_device.h>
+
+struct imx_weim {
+	void __iomem *base;
+	struct clk *clk;
+};
+
+static const struct of_device_id weim_id_table[] = {
+	{ .compatible = "fsl,imx6q-weim", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, weim_id_table);
+
+#define CS_TIMING_LEN 6
+#define CS_REG_RANGE  0x18
+
+/* Parse and set the timing for this device. */
+static int
+weim_timing_setup(struct platform_device *pdev, struct device_node *np)
+{
+	struct imx_weim *weim = platform_get_drvdata(pdev);
+	u32 value[CS_TIMING_LEN];
+	u32 cs_idx;
+	int ret;
+	int i;
+
+	/* get the CS index from this child node's "reg" property. */
+	ret = of_property_read_u32(np, "reg", &cs_idx);
+	if (ret)
+		return ret;
+
+	/* The weim has four chip selects. */
+	if (cs_idx > 3)
+		return -EINVAL;
+
+	ret = of_property_read_u32_array(np, "fsl,weim-cs-timing",
+					value, CS_TIMING_LEN);
+	if (ret)
+		return ret;
+
+	/* set the timing for WEIM */
+	for (i = 0; i < CS_TIMING_LEN; i++)
+		writel(value[i], weim->base + cs_idx * CS_REG_RANGE + i * 4);
+	return 0;
+}
+
+static int weim_parse_dt(struct platform_device *pdev)
+{
+	struct device_node *child;
+	int ret;
+
+	for_each_child_of_node(pdev->dev.of_node, child) {
+		if (!child->name)
+			continue;
+
+		ret = weim_timing_setup(pdev, child);
+		if (ret) {
+			dev_err(&pdev->dev, "%s set timing failed.\n",
+				child->full_name);
+			return ret;
+		}
+	}
+
+	ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
+	if (ret)
+		dev_err(&pdev->dev, "%s fail to create devices.\n",
+			pdev->dev.of_node->full_name);
+	return ret;
+}
+
+static int weim_probe(struct platform_device *pdev)
+{
+	struct imx_weim *weim;
+	struct resource *res;
+	int ret = -EINVAL;
+
+	weim = devm_kzalloc(&pdev->dev, sizeof(*weim), GFP_KERNEL);
+	if (!weim) {
+		ret = -ENOMEM;
+		goto weim_err;
+	}
+	platform_set_drvdata(pdev, weim);
+
+	/* get the resource */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	weim->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(weim->base)) {
+		ret = PTR_ERR(weim->base);
+		goto weim_err;
+	}
+
+	/* get the clock */
+	weim->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(weim->clk))
+		goto weim_err;
+
+	ret = clk_prepare_enable(weim->clk);
+	if (ret)
+		goto weim_err;
+
+	/* parse the device node */
+	ret = weim_parse_dt(pdev);
+	if (ret) {
+		clk_disable_unprepare(weim->clk);
+		goto weim_err;
+	}
+
+	dev_info(&pdev->dev, "WEIM driver registered.\n");
+	return 0;
+
+weim_err:
+	return ret;
+}
+
+static struct platform_driver weim_driver = {
+	.driver = {
+		.name = "imx-weim",
+		.of_match_table = weim_id_table,
+	},
+	.probe   = weim_probe,
+};
+
+module_platform_driver(weim_driver);
+MODULE_AUTHOR("Freescale Semiconductor Inc.");
+MODULE_DESCRIPTION("i.MX EIM Controller Driver");
+MODULE_LICENSE("GPL");