drivers: memory: Introduce Marvell EBU Device Bus driver

Marvell EBU SoCs such as Armada 370/XP, Orion5x (88f5xxx) and
Discovery (mv78xx0) supports a Device Bus controller to access several
kinds of memories and I/O devices (NOR, NAND, SRAM, FPGA).

This commit adds a driver to handle this controller. So far only
Armada 370, Armada XP and Discovery SoCs are supported.

The driver must be registered through a device tree node;
as explained in the binding document.

For each child node in the device tree, this driver will:
  * set timing parameters
  * register a child device
  * setup an address decoding window, using the mbus driver

Keep in mind the address decoding window setup is only a temporary hack.
This code will be removed from this devbus driver as soon as a proper device
tree binding for the mbus driver is added.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt

@@ -0,0 +1,156 @@
+Device tree bindings for MVEBU Device Bus controllers
+
+The Device Bus controller available in some Marvell's SoC allows to control
+different types of standard memory and I/O devices such as NOR, NAND, and FPGA.
+The actual devices are instantiated from the child nodes of a Device Bus node.
+
+Required properties:
+
+ - compatible:          Currently only Armada 370/XP SoC are supported,
+                        with this compatible string:
+
+                        marvell,mvebu-devbus
+
+ - reg:                 A resource specifier for the register space.
+                        This is the base address of a chip select within
+			the controller's register space.
+                        (see the example below)
+
+ - #address-cells:      Must be set to 1
+ - #size-cells:         Must be set to 1
+ - ranges:              Must be set up to reflect the memory layout with four
+                        integer values for each chip-select line in use:
+                        0 <physical address of mapping> <size>
+
+Mandatory timing properties for child nodes:
+
+Read parameters:
+
+ - devbus,turn-off-ps:  Defines the time during which the controller does not
+                        drive the AD bus after the completion of a device read.
+                        This prevents contentions on the Device Bus after a read
+                        cycle from a slow device.
+
+ - devbus,bus-width:    Defines the bus width (e.g. <16>)
+
+ - devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle,
+                        to read data sample. This parameter is useful for
+                        synchronous pipelined devices, where the address
+                        precedes the read data by one or two cycles.
+
+ - devbus,acc-first-ps: Defines the time delay from the negation of
+                        ALE[0] to the cycle that the first read data is sampled
+                        by the controller.
+
+ - devbus,acc-next-ps:  Defines the time delay between the cycle that
+                        samples data N and the cycle that samples data N+1
+                        (in burst accesses).
+
+ - devbus,rd-setup-ps:  Defines the time delay between DEV_CSn assertion to
+			DEV_OEn assertion. If set to 0 (default),
+                        DEV_OEn and DEV_CSn are asserted at the same cycle.
+                        This parameter has no affect on <acc-first-ps> parameter
+                        (no affect on first data sample). Set <rd-setup-ps>
+                        to a value smaller than <acc-first-ps>.
+
+ - devbus,rd-hold-ps:   Defines the time between the last data sample to the
+			de-assertion of DEV_CSn. If set to 0 (default),
+			DEV_OEn and DEV_CSn are de-asserted at the same cycle
+			(the cycle of the last data sample).
+                        This parameter has no affect on DEV_OEn de-assertion.
+                        DEV_OEn is always de-asserted the next cycle after
+                        last data sampled. Also this parameter has no
+                        affect on <turn-off-ps> parameter.
+                        Set <rd-hold-ps> to a value smaller than <turn-off-ps>.
+
+Write parameters:
+
+ - devbus,ale-wr-ps:    Defines the time delay from the ALE[0] negation cycle
+			to the DEV_WEn assertion.
+
+ - devbus,wr-low-ps:    Defines the time during which DEV_WEn is active.
+                        A[2:0] and Data are kept valid as long as DEV_WEn
+                        is active. This parameter defines the setup time of
+                        address and data to DEV_WEn rise.
+
+ - devbus,wr-high-ps:   Defines the time during which DEV_WEn is kept
+                        inactive (high) between data beats of a burst write.
+                        DEV_A[2:0] and Data are kept valid (do not toggle) for
+                        <wr-high-ps> - <tick> ps.
+			This parameter defines the hold time of address and
+			data after DEV_WEn rise.
+
+ - devbus,sync-enable: Synchronous device enable.
+                       1: True
+                       0: False
+
+An example for an Armada XP GP board, with a 16 MiB NOR device as child
+is showed below. Note that the Device Bus driver is in charge of allocating
+the mbus address decoding window for each of its child devices.
+The window is created using the chip select specified in the child
+device node together with the base address and size specified in the ranges
+property. For instance, in the example below the allocated decoding window
+will start at base address 0xf0000000, with a size 0x1000000 (16 MiB)
+for chip select 0 (a.k.a DEV_BOOTCS).
+
+This address window handling is done in this mvebu-devbus only as a temporary
+solution. It will be removed when the support for mbus device tree binding is
+added.
+
+The reg property implicitly specifies the chip select as this:
+
+  0x10400: DEV_BOOTCS
+  0x10408: DEV_CS0
+  0x10410: DEV_CS1
+  0x10418: DEV_CS2
+  0x10420: DEV_CS3
+
+Example:
+
+	devbus-bootcs@d0010400 {
+		status = "okay";
+		ranges = <0 0xf0000000 0x1000000>; /* @addr 0xf0000000, size 0x1000000 */
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		/* Device Bus parameters are required */
+
+		/* Read parameters */
+		devbus,bus-width    = <8>;
+		devbus,turn-off-ps  = <60000>;
+		devbus,badr-skew-ps = <0>;
+		devbus,acc-first-ps = <124000>;
+		devbus,acc-next-ps  = <248000>;
+		devbus,rd-setup-ps  = <0>;
+		devbus,rd-hold-ps   = <0>;
+
+		/* Write parameters */
+		devbus,sync-enable = <0>;
+		devbus,wr-high-ps  = <60000>;
+		devbus,wr-low-ps   = <60000>;
+		devbus,ale-wr-ps   = <60000>;
+
+		flash@0 {
+			compatible = "cfi-flash";
+
+			/* 16 MiB */
+			reg = <0 0x1000000>;
+			bank-width = <2>;
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			/*
+			 * We split the 16 MiB in two partitions,
+			 * just as an example.
+			 */
+			partition@0 {
+				label = "First";
+				reg = <0 0x800000>;
+			};
+
+			partition@800000 {
+				label = "Second";
+				reg = <0x800000 0x800000>;
+			};
+		};
+	};

drivers/memory/Kconfig

@@ -20,6 +20,16 @@ config TI_EMIF
 	  parameters and other settings during frequency, voltage and
 	  temperature changes
 
+config MVEBU_DEVBUS
+	bool "Marvell EBU Device Bus Controller"
+	default y
+	depends on PLAT_ORION && OF
+	help
+	  This driver is for the Device Bus controller available in some
+	  Marvell EBU SoCs such as Discovery (mv78xx0), Orion (88f5xxx) and
+	  Armada 370 and Armada XP. This controller allows to handle flash
+	  devices such as NOR, NAND, SRAM, and FPGA.
+
 config TEGRA20_MC
 	bool "Tegra20 Memory Controller(MC) driver"
 	default y

drivers/memory/Makefile

@@ -6,5 +6,6 @@ ifeq ($(CONFIG_DDR),y)
 obj-$(CONFIG_OF)		+= of_memory.o
 endif
 obj-$(CONFIG_TI_EMIF)		+= emif.o
+obj-$(CONFIG_MVEBU_DEVBUS)	+= mvebu-devbus.o
 obj-$(CONFIG_TEGRA20_MC)	+= tegra20-mc.o
 obj-$(CONFIG_TEGRA30_MC)	+= tegra30-mc.o

drivers/memory/mvebu-devbus.c

@@ -0,0 +1,340 @@
+/*
+ * Marvell EBU SoC Device Bus Controller
+ * (memory controller for NOR/NAND/SRAM/FPGA devices)
+ *
+ * Copyright (C) 2013 Marvell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/mbus.h>
+#include <linux/of_platform.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+
+/* Register definitions */
+#define DEV_WIDTH_BIT		30
+#define BADR_SKEW_BIT		28
+#define RD_HOLD_BIT		23
+#define ACC_NEXT_BIT		17
+#define RD_SETUP_BIT		12
+#define ACC_FIRST_BIT		6
+
+#define SYNC_ENABLE_BIT		24
+#define WR_HIGH_BIT		16
+#define WR_LOW_BIT		8
+
+#define READ_PARAM_OFFSET	0x0
+#define WRITE_PARAM_OFFSET	0x4
+
+static const char * const devbus_wins[] = {
+	"devbus-boot",
+	"devbus-cs0",
+	"devbus-cs1",
+	"devbus-cs2",
+	"devbus-cs3",
+};
+
+struct devbus_read_params {
+	u32 bus_width;
+	u32 badr_skew;
+	u32 turn_off;
+	u32 acc_first;
+	u32 acc_next;
+	u32 rd_setup;
+	u32 rd_hold;
+};
+
+struct devbus_write_params {
+	u32 sync_enable;
+	u32 wr_high;
+	u32 wr_low;
+	u32 ale_wr;
+};
+
+struct devbus {
+	struct device *dev;
+	void __iomem *base;
+	unsigned long tick_ps;
+};
+
+static int get_timing_param_ps(struct devbus *devbus,
+			       struct device_node *node,
+			       const char *name,
+			       u32 *ticks)
+{
+	u32 time_ps;
+	int err;
+
+	err = of_property_read_u32(node, name, &time_ps);
+	if (err < 0) {
+		dev_err(devbus->dev, "%s has no '%s' property\n",
+			name, node->full_name);
+		return err;
+	}
+
+	*ticks = (time_ps + devbus->tick_ps - 1) / devbus->tick_ps;
+
+	dev_dbg(devbus->dev, "%s: %u ps -> 0x%x\n",
+		name, time_ps, *ticks);
+	return 0;
+}
+
+static int devbus_set_timing_params(struct devbus *devbus,
+				    struct device_node *node)
+{
+	struct devbus_read_params r;
+	struct devbus_write_params w;
+	u32 value;
+	int err;
+
+	dev_dbg(devbus->dev, "Setting timing parameter, tick is %lu ps\n",
+		devbus->tick_ps);
+
+	/* Get read timings */
+	err = of_property_read_u32(node, "devbus,bus-width", &r.bus_width);
+	if (err < 0) {
+		dev_err(devbus->dev,
+			"%s has no 'devbus,bus-width' property\n",
+			node->full_name);
+		return err;
+	}
+	/* Convert bit width to byte width */
+	r.bus_width /= 8;
+
+	err = get_timing_param_ps(devbus, node, "devbus,badr-skew-ps",
+				 &r.badr_skew);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,turn-off-ps",
+				 &r.turn_off);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,acc-first-ps",
+				 &r.acc_first);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,acc-next-ps",
+				 &r.acc_next);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,rd-setup-ps",
+				 &r.rd_setup);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,rd-hold-ps",
+				 &r.rd_hold);
+	if (err < 0)
+		return err;
+
+	/* Get write timings */
+	err = of_property_read_u32(node, "devbus,sync-enable",
+				  &w.sync_enable);
+	if (err < 0) {
+		dev_err(devbus->dev,
+			"%s has no 'devbus,sync-enable' property\n",
+			node->full_name);
+		return err;
+	}
+
+	err = get_timing_param_ps(devbus, node, "devbus,ale-wr-ps",
+				 &w.ale_wr);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,wr-low-ps",
+				 &w.wr_low);
+	if (err < 0)
+		return err;
+
+	err = get_timing_param_ps(devbus, node, "devbus,wr-high-ps",
+				 &w.wr_high);
+	if (err < 0)
+		return err;
+
+	/* Set read timings */
+	value = r.bus_width << DEV_WIDTH_BIT |
+		r.badr_skew << BADR_SKEW_BIT |
+		r.rd_hold   << RD_HOLD_BIT   |
+		r.acc_next  << ACC_NEXT_BIT  |
+		r.rd_setup  << RD_SETUP_BIT  |
+		r.acc_first << ACC_FIRST_BIT |
+		r.turn_off;
+
+	dev_dbg(devbus->dev, "read parameters register 0x%p = 0x%x\n",
+		devbus->base + READ_PARAM_OFFSET,
+		value);
+
+	writel(value, devbus->base + READ_PARAM_OFFSET);
+
+	/* Set write timings */
+	value = w.sync_enable  << SYNC_ENABLE_BIT |
+		w.wr_low       << WR_LOW_BIT      |
+		w.wr_high      << WR_HIGH_BIT     |
+		w.ale_wr;
+
+	dev_dbg(devbus->dev, "write parameters register: 0x%p = 0x%x\n",
+		devbus->base + WRITE_PARAM_OFFSET,
+		value);
+
+	writel(value, devbus->base + WRITE_PARAM_OFFSET);
+
+	return 0;
+}
+
+static int mvebu_devbus_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = pdev->dev.of_node;
+	struct device_node *parent;
+	struct devbus *devbus;
+	struct resource *res;
+	struct clk *clk;
+	unsigned long rate;
+	const __be32 *ranges;
+	int err, cs;
+	int addr_cells, p_addr_cells, size_cells;
+	int ranges_len, tuple_len;
+	u32 base, size;
+
+	devbus = devm_kzalloc(&pdev->dev, sizeof(struct devbus), GFP_KERNEL);
+	if (!devbus)
+		return -ENOMEM;
+
+	devbus->dev = dev;
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	devbus->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(devbus->base))
+		return PTR_ERR(devbus->base);
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+	clk_prepare_enable(clk);
+
+	/*
+	 * Obtain clock period in picoseconds,
+	 * we need this in order to convert timing
+	 * parameters from cycles to picoseconds.
+	 */
+	rate = clk_get_rate(clk) / 1000;
+	devbus->tick_ps = 1000000000 / rate;
+
+	/* Read the device tree node and set the new timing parameters */
+	err = devbus_set_timing_params(devbus, node);
+	if (err < 0)
+		return err;
+
+	/*
+	 * Allocate an address window for this device.
+	 * If the device probing fails, then we won't be able to
+	 * remove the allocated address decoding window.
+	 *
+	 * FIXME: This is only a temporary hack! We need to do this here
+	 * because we still don't have device tree bindings for mbus.
+	 * Once that support is added, we will declare these address windows
+	 * statically in the device tree, and remove the window configuration
+	 * from here.
+	 */
+
+	/*
+	 * Get the CS to choose the window string.
+	 * This is a bit hacky, but it will be removed once the
+	 * address windows are declared in the device tree.
+	 */
+	cs = (((unsigned long)devbus->base) % 0x400) / 8;
+
+	/*
+	 * Parse 'ranges' property to obtain a (base,size) window tuple.
+	 * This will be removed once the address windows
+	 * are declared in the device tree.
+	 */
+	parent = of_get_parent(node);
+	if (!parent)
+		return -EINVAL;
+
+	p_addr_cells = of_n_addr_cells(parent);
+	of_node_put(parent);
+
+	addr_cells = of_n_addr_cells(node);
+	size_cells = of_n_size_cells(node);
+	tuple_len = (p_addr_cells + addr_cells + size_cells) * sizeof(__be32);
+
+	ranges = of_get_property(node, "ranges", &ranges_len);
+	if (ranges == NULL || ranges_len != tuple_len)
+		return -EINVAL;
+
+	base = of_translate_address(node, ranges + addr_cells);
+	if (base == OF_BAD_ADDR)
+		return -EINVAL;
+	size = of_read_number(ranges + addr_cells + p_addr_cells, size_cells);
+
+	/*
+	 * Create an mbus address windows.
+	 * FIXME: Remove this, together with the above code, once the
+	 * address windows are declared in the device tree.
+	 */
+	err = mvebu_mbus_add_window(devbus_wins[cs], base, size);
+	if (err < 0)
+		return err;
+
+	/*
+	 * We need to create a child device explicitly from here to
+	 * guarantee that the child will be probed after the timing
+	 * parameters for the bus are written.
+	 */
+	err = of_platform_populate(node, NULL, NULL, dev);
+	if (err < 0) {
+		mvebu_mbus_del_window(base, size);
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mvebu_devbus_of_match[] = {
+	{ .compatible = "marvell,mvebu-devbus" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mvebu_devbus_of_match);
+
+static struct platform_driver mvebu_devbus_driver = {
+	.probe		= mvebu_devbus_probe,
+	.driver		= {
+		.name	= "mvebu-devbus",
+		.owner	= THIS_MODULE,
+		.of_match_table = mvebu_devbus_of_match,
+	},
+};
+
+static int __init mvebu_devbus_init(void)
+{
+	return platform_driver_register(&mvebu_devbus_driver);
+}
+module_init(mvebu_devbus_init);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Ezequiel Garcia <ezequiel.garcia@free-electrons.com>");
+MODULE_DESCRIPTION("Marvell EBU SoC Device Bus controller");