bus: ixp4xx: Add a driver for IXP4xx expansion bus

The Intel IXP4xx SoCs have an expansion bus that is usually just
used for flash memory and configured by the boot loaders and can
be accessed using the "simple-bus".

However some devices need more elaborate configuration and then we
need to provide a proper 3-unit address space indicating chip
select for each device and provide timing and similar information.

Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -2009,10 +2009,12 @@ M:	Krzysztof Halasa <khalasa@piap.pl>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 F:	Documentation/devicetree/bindings/arm/intel-ixp4xx.yaml
+F:	Documentation/devicetree/bindings/bus/intel,ixp4xx-expansion-bus-controller.yaml
 F:	Documentation/devicetree/bindings/gpio/intel,ixp4xx-gpio.txt
 F:	Documentation/devicetree/bindings/interrupt-controller/intel,ixp4xx-interrupt.yaml
 F:	Documentation/devicetree/bindings/timer/intel,ixp4xx-timer.yaml
 F:	arch/arm/mach-ixp4xx/
+F:	drivers/bus/intel-ixp4xx-eb.c
 F:	drivers/clocksource/timer-ixp4xx.c
 F:	drivers/crypto/ixp4xx_crypto.c
 F:	drivers/gpio/gpio-ixp4xx.c

drivers/bus/Kconfig

@@ -95,6 +95,17 @@ config IMX_WEIM
 	  The WEIM(Wireless External Interface Module) works like a bus.
 	  You can attach many different devices on it, such as NOR, onenand.
 
+config INTEL_IXP4XX_EB
+	bool "Intel IXP4xx expansion bus interface driver"
+	depends on HAS_IOMEM
+	depends on ARCH_IXP4XX || COMPILE_TEST
+	default ARCH_IXP4XX
+	select MFD_SYSCON
+	help
+	  Driver for the Intel IXP4xx expansion bus interface. The driver is
+	  needed to set up various chip select configuration parameters before
+	  devices on the expansion bus can be discovered.
+
 config MIPS_CDMM
 	bool "MIPS Common Device Memory Map (CDMM) Driver"
 	depends on CPU_MIPSR2 || CPU_MIPSR5

drivers/bus/Makefile

@@ -16,6 +16,7 @@ obj-$(CONFIG_FSL_MC_BUS)	+= fsl-mc/
 obj-$(CONFIG_BT1_APB)		+= bt1-apb.o
 obj-$(CONFIG_BT1_AXI)		+= bt1-axi.o
 obj-$(CONFIG_IMX_WEIM)		+= imx-weim.o
+obj-$(CONFIG_INTEL_IXP4XX_EB)	+= intel-ixp4xx-eb.o
 obj-$(CONFIG_MIPS_CDMM)		+= mips_cdmm.o
 obj-$(CONFIG_MVEBU_MBUS) 	+= mvebu-mbus.o
 

drivers/bus/intel-ixp4xx-eb.c

@@ -0,0 +1,429 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Intel IXP4xx Expansion Bus Controller
+ * Copyright (C) 2021 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/log2.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define IXP4XX_EXP_NUM_CS		8
+
+#define IXP4XX_EXP_TIMING_CS0		0x00
+#define IXP4XX_EXP_TIMING_CS1		0x04
+#define IXP4XX_EXP_TIMING_CS2		0x08
+#define IXP4XX_EXP_TIMING_CS3		0x0c
+#define IXP4XX_EXP_TIMING_CS4		0x10
+#define IXP4XX_EXP_TIMING_CS5		0x14
+#define IXP4XX_EXP_TIMING_CS6		0x18
+#define IXP4XX_EXP_TIMING_CS7		0x1c
+
+/* Bits inside each CS timing register */
+#define IXP4XX_EXP_TIMING_STRIDE	0x04
+#define IXP4XX_EXP_CS_EN		BIT(31)
+#define IXP456_EXP_PAR_EN		BIT(30) /* Only on IXP45x and IXP46x */
+#define IXP4XX_EXP_T1_MASK		GENMASK(28, 27)
+#define IXP4XX_EXP_T1_SHIFT		28
+#define IXP4XX_EXP_T2_MASK		GENMASK(27, 26)
+#define IXP4XX_EXP_T2_SHIFT		26
+#define IXP4XX_EXP_T3_MASK		GENMASK(25, 22)
+#define IXP4XX_EXP_T3_SHIFT		22
+#define IXP4XX_EXP_T4_MASK		GENMASK(21, 20)
+#define IXP4XX_EXP_T4_SHIFT		20
+#define IXP4XX_EXP_T5_MASK		GENMASK(19, 16)
+#define IXP4XX_EXP_T5_SHIFT		16
+#define IXP4XX_EXP_CYC_TYPE_MASK	GENMASK(15, 14)
+#define IXP4XX_EXP_CYC_TYPE_SHIFT	14
+#define IXP4XX_EXP_SIZE_MASK		GENMASK(13, 10)
+#define IXP4XX_EXP_SIZE_SHIFT		10
+#define IXP4XX_EXP_CNFG_0		BIT(9) /* Always zero */
+#define IXP43X_EXP_SYNC_INTEL		BIT(8) /* Only on IXP43x */
+#define IXP43X_EXP_EXP_CHIP		BIT(7) /* Only on IXP43x */
+#define IXP4XX_EXP_BYTE_RD16		BIT(6)
+#define IXP4XX_EXP_HRDY_POL		BIT(5) /* Only on IXP42x */
+#define IXP4XX_EXP_MUX_EN		BIT(4)
+#define IXP4XX_EXP_SPLT_EN		BIT(3)
+#define IXP4XX_EXP_WORD			BIT(2) /* Always zero */
+#define IXP4XX_EXP_WR_EN		BIT(1)
+#define IXP4XX_EXP_BYTE_EN		BIT(0)
+#define IXP42X_RESERVED			(BIT(30)|IXP4XX_EXP_CNFG_0|BIT(8)|BIT(7)|IXP4XX_EXP_WORD)
+#define IXP43X_RESERVED			(BIT(30)|IXP4XX_EXP_CNFG_0|BIT(5)|IXP4XX_EXP_WORD)
+
+#define IXP4XX_EXP_CNFG0		0x20
+#define IXP4XX_EXP_CNFG0_MEM_MAP	BIT(31)
+#define IXP4XX_EXP_CNFG1		0x24
+
+#define IXP4XX_EXP_BOOT_BASE		0x00000000
+#define IXP4XX_EXP_NORMAL_BASE		0x50000000
+#define IXP4XX_EXP_STRIDE		0x01000000
+
+/* Fuses on the IXP43x */
+#define IXP43X_EXP_UNIT_FUSE_RESET	0x28
+#define IXP43x_EXP_FUSE_SPEED_MASK	GENMASK(23, 22)
+
+/* Number of device tree values in "reg" */
+#define IXP4XX_OF_REG_SIZE		3
+
+struct ixp4xx_eb {
+	struct device *dev;
+	struct regmap *rmap;
+	u32 bus_base;
+	bool is_42x;
+	bool is_43x;
+};
+
+struct ixp4xx_exp_tim_prop {
+	const char *prop;
+	u32 max;
+	u32 mask;
+	u16 shift;
+};
+
+static const struct ixp4xx_exp_tim_prop ixp4xx_exp_tim_props[] = {
+	{
+		.prop = "intel,ixp4xx-eb-t1",
+		.max = 3,
+		.mask = IXP4XX_EXP_T1_MASK,
+		.shift = IXP4XX_EXP_T1_SHIFT,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-t2",
+		.max = 3,
+		.mask = IXP4XX_EXP_T2_MASK,
+		.shift = IXP4XX_EXP_T2_SHIFT,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-t3",
+		.max = 15,
+		.mask = IXP4XX_EXP_T3_MASK,
+		.shift = IXP4XX_EXP_T3_SHIFT,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-t4",
+		.max = 3,
+		.mask = IXP4XX_EXP_T4_MASK,
+		.shift = IXP4XX_EXP_T4_SHIFT,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-t5",
+		.max = 15,
+		.mask = IXP4XX_EXP_T5_MASK,
+		.shift = IXP4XX_EXP_T5_SHIFT,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-byte-access-on-halfword",
+		.max = 1,
+		.mask = IXP4XX_EXP_BYTE_RD16,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-hpi-hrdy-pol-high",
+		.max = 1,
+		.mask = IXP4XX_EXP_HRDY_POL,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-mux-address-and-data",
+		.max = 1,
+		.mask = IXP4XX_EXP_MUX_EN,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-ahb-split-transfers",
+		.max = 1,
+		.mask = IXP4XX_EXP_SPLT_EN,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-write-enable",
+		.max = 1,
+		.mask = IXP4XX_EXP_WR_EN,
+	},
+	{
+		.prop = "intel,ixp4xx-eb-byte-access",
+		.max = 1,
+		.mask = IXP4XX_EXP_BYTE_EN,
+	},
+};
+
+static void ixp4xx_exp_setup_chipselect(struct ixp4xx_eb *eb,
+					struct device_node *np,
+					u32 cs_index,
+					u32 cs_size)
+{
+	u32 cs_cfg;
+	u32 val;
+	u32 cur_cssize;
+	u32 cs_order;
+	int ret;
+	int i;
+
+	if (eb->is_42x && (cs_index > 7)) {
+		dev_err(eb->dev,
+			"invalid chipselect %u, we only support 0-7\n",
+			cs_index);
+		return;
+	}
+	if (eb->is_43x && (cs_index > 3)) {
+		dev_err(eb->dev,
+			"invalid chipselect %u, we only support 0-3\n",
+			cs_index);
+		return;
+	}
+
+	/* Several chip selects can be joined into one device */
+	if (cs_size > IXP4XX_EXP_STRIDE)
+		cur_cssize = IXP4XX_EXP_STRIDE;
+	else
+		cur_cssize = cs_size;
+
+
+	/*
+	 * The following will read/modify/write the configuration for one
+	 * chipselect, attempting to leave the boot defaults in place unless
+	 * something is explicitly defined.
+	 */
+	regmap_read(eb->rmap, IXP4XX_EXP_TIMING_CS0 +
+		    IXP4XX_EXP_TIMING_STRIDE * cs_index, &cs_cfg);
+	dev_info(eb->dev, "CS%d at %#08x, size %#08x, config before: %#08x\n",
+		 cs_index, eb->bus_base + IXP4XX_EXP_STRIDE * cs_index,
+		 cur_cssize, cs_cfg);
+
+	/* Size set-up first align to 2^9 .. 2^24 */
+	cur_cssize = roundup_pow_of_two(cur_cssize);
+	if (cur_cssize < 512)
+		cur_cssize = 512;
+	cs_order = ilog2(cur_cssize);
+	if (cs_order < 9 || cs_order > 24) {
+		dev_err(eb->dev, "illegal size order %d\n", cs_order);
+		return;
+	}
+	dev_dbg(eb->dev, "CS%d size order: %d\n", cs_index, cs_order);
+	cs_cfg &= ~(IXP4XX_EXP_SIZE_MASK);
+	cs_cfg |= ((cs_order - 9) << IXP4XX_EXP_SIZE_SHIFT);
+
+	for (i = 0; i < ARRAY_SIZE(ixp4xx_exp_tim_props); i++) {
+		const struct ixp4xx_exp_tim_prop *ip = &ixp4xx_exp_tim_props[i];
+
+		/* All are regular u32 values */
+		ret = of_property_read_u32(np, ip->prop, &val);
+		if (ret)
+			continue;
+
+		/* Handle bools (single bits) first */
+		if (ip->max == 1) {
+			if (val)
+				cs_cfg |= ip->mask;
+			else
+				cs_cfg &= ~ip->mask;
+			dev_info(eb->dev, "CS%d %s %s\n", cs_index,
+				 val ? "enabled" : "disabled",
+				 ip->prop);
+			continue;
+		}
+
+		if (val > ip->max) {
+			dev_err(eb->dev,
+				"CS%d too high value for %s: %u, capped at %u\n",
+				cs_index, ip->prop, val, ip->max);
+			val = ip->max;
+		}
+		/* This assumes max value fills all the assigned bits (and it does) */
+		cs_cfg &= ~ip->mask;
+		cs_cfg |= (val << ip->shift);
+		dev_info(eb->dev, "CS%d set %s to %u\n", cs_index, ip->prop, val);
+	}
+
+	ret = of_property_read_u32(np, "intel,ixp4xx-eb-cycle-type", &val);
+	if (!ret) {
+		if (val > 3) {
+			dev_err(eb->dev, "illegal cycle type %d\n", val);
+			return;
+		}
+		dev_info(eb->dev, "CS%d set cycle type %d\n", cs_index, val);
+		cs_cfg &= ~IXP4XX_EXP_CYC_TYPE_MASK;
+		cs_cfg |= val << IXP4XX_EXP_CYC_TYPE_SHIFT;
+	}
+
+	if (eb->is_42x)
+		cs_cfg &= ~IXP42X_RESERVED;
+	if (eb->is_43x) {
+		cs_cfg &= ~IXP43X_RESERVED;
+		/*
+		 * This bit for Intel strata flash is currently unused, but let's
+		 * report it if we find one.
+		 */
+		if (cs_cfg & IXP43X_EXP_SYNC_INTEL)
+			dev_info(eb->dev, "claims to be Intel strata flash\n");
+	}
+	cs_cfg |= IXP4XX_EXP_CS_EN;
+
+	regmap_write(eb->rmap,
+		     IXP4XX_EXP_TIMING_CS0 + IXP4XX_EXP_TIMING_STRIDE * cs_index,
+		     cs_cfg);
+	dev_info(eb->dev, "CS%d wrote %#08x into CS config\n", cs_index, cs_cfg);
+
+	/*
+	 * If several chip selects are joined together into one big
+	 * device area, we call ourselves recursively for each successive
+	 * chip select. For a 32MB flash chip this results in two calls
+	 * for example.
+	 */
+	if (cs_size > IXP4XX_EXP_STRIDE)
+		ixp4xx_exp_setup_chipselect(eb, np,
+					    cs_index + 1,
+					    cs_size - IXP4XX_EXP_STRIDE);
+}
+
+static void ixp4xx_exp_setup_child(struct ixp4xx_eb *eb,
+				   struct device_node *np)
+{
+	u32 cs_sizes[IXP4XX_EXP_NUM_CS];
+	int num_regs;
+	u32 csindex;
+	u32 cssize;
+	int ret;
+	int i;
+
+	num_regs = of_property_count_elems_of_size(np, "reg", IXP4XX_OF_REG_SIZE);
+	if (num_regs <= 0)
+		return;
+	dev_dbg(eb->dev, "child %s has %d register sets\n",
+		of_node_full_name(np), num_regs);
+
+	for (csindex = 0; csindex < IXP4XX_EXP_NUM_CS; csindex++)
+		cs_sizes[csindex] = 0;
+
+	for (i = 0; i < num_regs; i++) {
+		u32 rbase, rsize;
+
+		ret = of_property_read_u32_index(np, "reg",
+						 i * IXP4XX_OF_REG_SIZE, &csindex);
+		if (ret)
+			break;
+		ret = of_property_read_u32_index(np, "reg",
+						 i * IXP4XX_OF_REG_SIZE + 1, &rbase);
+		if (ret)
+			break;
+		ret = of_property_read_u32_index(np, "reg",
+						 i * IXP4XX_OF_REG_SIZE + 2, &rsize);
+		if (ret)
+			break;
+
+		if (csindex >= IXP4XX_EXP_NUM_CS) {
+			dev_err(eb->dev, "illegal CS %d\n", csindex);
+			continue;
+		}
+		/*
+		 * The memory window always starts from CS base so we need to add
+		 * the start and size to get to the size from the start of the CS
+		 * base. For example if CS0 is at 0x50000000 and the reg is
+		 * <0 0xe40000 0x40000> the size is e80000.
+		 *
+		 * Roof this if we have several regs setting the same CS.
+		 */
+		cssize = rbase + rsize;
+		dev_dbg(eb->dev, "CS%d size %#08x\n", csindex, cssize);
+		if (cs_sizes[csindex] < cssize)
+			cs_sizes[csindex] = cssize;
+	}
+
+	for (csindex = 0; csindex < IXP4XX_EXP_NUM_CS; csindex++) {
+		cssize = cs_sizes[csindex];
+		if (!cssize)
+			continue;
+		/* Just this one, so set it up and return */
+		ixp4xx_exp_setup_chipselect(eb, np, csindex, cssize);
+	}
+}
+
+static int ixp4xx_exp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct ixp4xx_eb *eb;
+	struct device_node *child;
+	bool have_children = false;
+	u32 val;
+	int ret;
+
+	eb = devm_kzalloc(dev, sizeof(*eb), GFP_KERNEL);
+	if (!eb)
+		return -ENOMEM;
+
+	eb->dev = dev;
+	eb->is_42x = of_device_is_compatible(np, "intel,ixp42x-expansion-bus-controller");
+	eb->is_43x = of_device_is_compatible(np, "intel,ixp43x-expansion-bus-controller");
+
+	eb->rmap = syscon_node_to_regmap(np);
+	if (IS_ERR(eb->rmap))
+		return dev_err_probe(dev, PTR_ERR(eb->rmap), "no regmap\n");
+
+	/* We check that the regmap work only on first read */
+	ret = regmap_read(eb->rmap, IXP4XX_EXP_CNFG0, &val);
+	if (ret)
+		dev_err_probe(dev, ret, "cannot read regmap\n");
+	if (val & IXP4XX_EXP_CNFG0_MEM_MAP)
+		eb->bus_base = IXP4XX_EXP_BOOT_BASE;
+	else
+		eb->bus_base = IXP4XX_EXP_NORMAL_BASE;
+	dev_info(dev, "expansion bus at %08x\n", eb->bus_base);
+
+	if (eb->is_43x) {
+		/* Check some fuses */
+		regmap_read(eb->rmap, IXP43X_EXP_UNIT_FUSE_RESET, &val);
+		switch (FIELD_GET(IXP43x_EXP_FUSE_SPEED_MASK, val)) {
+		case 0:
+			dev_info(dev, "IXP43x at 533 MHz\n");
+			break;
+		case 1:
+			dev_info(dev, "IXP43x at 400 MHz\n");
+			break;
+		case 2:
+			dev_info(dev, "IXP43x at 667 MHz\n");
+			break;
+		default:
+			dev_info(dev, "IXP43x unknown speed\n");
+			break;
+		}
+	}
+
+	/* Walk over the child nodes and see what chipselects we use */
+	for_each_available_child_of_node(np, child) {
+		ixp4xx_exp_setup_child(eb, child);
+		/* We have at least one child */
+		have_children = true;
+	}
+
+	if (have_children)
+		return of_platform_default_populate(np, NULL, dev);
+
+	return 0;
+}
+
+static const struct of_device_id ixp4xx_exp_of_match[] = {
+	{ .compatible = "intel,ixp42x-expansion-bus-controller", },
+	{ .compatible = "intel,ixp43x-expansion-bus-controller", },
+	{ .compatible = "intel,ixp45x-expansion-bus-controller", },
+	{ .compatible = "intel,ixp46x-expansion-bus-controller", },
+	{ }
+};
+
+static struct platform_driver ixp4xx_exp_driver = {
+	.probe = ixp4xx_exp_probe,
+	.driver = {
+		.name = "intel-extbus",
+		.of_match_table = ixp4xx_exp_of_match,
+	},
+};
+module_platform_driver(ixp4xx_exp_driver);
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("Intel IXP4xx external bus driver");
+MODULE_LICENSE("GPL");