C6X: DSCR - Device State Configuration Registers

All SoCs provide an area of device configuration registers called the DSCR. The
location of specific registers as well as their use varies considerably from
implementation to implementation. Rather than having to rely on additional
SoC-specific DSCR code for each new supported SoC, this code generalize things
as much as possible using device tree properties. Initialization must take
place early on (setup_arch time) in case the event timer device needs to be
enable via the DSCR.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/c6x/include/asm/dscr.h

@@ -0,0 +1,34 @@
+/*
+ *  Copyright (C) 2011 Texas Instruments Incorporated
+ *  Author: Mark Salter <msalter@redhat.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.
+ *
+ */
+#ifndef _ASM_C6X_DSCR_H
+#define _ASM_C6X_DSCR_H
+
+enum dscr_devstate_t {
+	DSCR_DEVSTATE_ENABLED,
+	DSCR_DEVSTATE_DISABLED,
+};
+
+/*
+ * Set the device state of the device with the given ID.
+ *
+ * Individual drivers should use this to enable or disable the
+ * hardware device. The devid used to identify the device being
+ * controlled should be a property in the device's tree node.
+ */
+extern void dscr_set_devstate(int devid, enum dscr_devstate_t state);
+
+/*
+ * Assert or de-assert an RMII reset.
+ */
+extern void dscr_rmii_reset(int id, int assert);
+
+extern void dscr_probe(void);
+
+#endif /* _ASM_C6X_DSCR_H */

arch/c6x/platforms/dscr.c

@@ -0,0 +1,598 @@
+/*
+ *  Device State Control Registers driver
+ *
+ *  Copyright (C) 2011 Texas Instruments Incorporated
+ *  Author: Mark Salter <msalter@redhat.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.
+ */
+
+/*
+ * The Device State Control Registers (DSCR) provide SoC level control over
+ * a number of peripherals. Details vary considerably among the various SoC
+ * parts. In general, the DSCR block will provide one or more configuration
+ * registers often protected by a lock register. One or more key values must
+ * be written to a lock register in order to unlock the configuration register.
+ * The configuration register may be used to enable (and disable in some
+ * cases) SoC pin drivers, peripheral clock sources (internal or pin), etc.
+ * In some cases, a configuration register is write once or the individual
+ * bits are write once. That is, you may be able to enable a device, but
+ * will not be able to disable it.
+ *
+ * In addition to device configuration, the DSCR block may provide registers
+ * which are used to reset SoC peripherals, provide device ID information,
+ * provide MAC addresses, and other miscellaneous functions.
+ */
+
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <asm/soc.h>
+#include <asm/dscr.h>
+
+#define MAX_DEVSTATE_IDS   32
+#define MAX_DEVCTL_REGS     8
+#define MAX_DEVSTAT_REGS    8
+#define MAX_LOCKED_REGS     4
+#define MAX_SOC_EMACS       2
+
+struct rmii_reset_reg {
+	u32 reg;
+	u32 mask;
+};
+
+/*
+ * Some registerd may be locked. In order to write to these
+ * registers, the key value must first be written to the lockreg.
+ */
+struct locked_reg {
+	u32 reg;	/* offset from base */
+	u32 lockreg;	/* offset from base */
+	u32 key;	/* unlock key */
+};
+
+/*
+ * This describes a contiguous area of like control bits used to enable/disable
+ * SoC devices. Each controllable device is given an ID which is used by the
+ * individual device drivers to control the device state. These IDs start at
+ * zero and are assigned sequentially to the control bitfield ranges described
+ * by this structure.
+ */
+struct devstate_ctl_reg {
+	u32 reg;		/* register holding the control bits */
+	u8  start_id;		/* start id of this range */
+	u8  num_ids;		/* number of devices in this range */
+	u8  enable_only;	/* bits are write-once to enable only */
+	u8  enable;		/* value used to enable device */
+	u8  disable;		/* value used to disable device */
+	u8  shift;		/* starting (rightmost) bit in range */
+	u8  nbits;		/* number of bits per device */
+};
+
+
+/*
+ * This describes a region of status bits indicating the state of
+ * various devices. This is used internally to wait for status
+ * change completion when enabling/disabling a device. Status is
+ * optional and not all device controls will have a corresponding
+ * status.
+ */
+struct devstate_stat_reg {
+	u32 reg;		/* register holding the status bits */
+	u8  start_id;		/* start id of this range */
+	u8  num_ids;		/* number of devices in this range */
+	u8  enable;		/* value indicating enabled state */
+	u8  disable;		/* value indicating disabled state */
+	u8  shift;		/* starting (rightmost) bit in range */
+	u8  nbits;		/* number of bits per device */
+};
+
+struct devstate_info {
+	struct devstate_ctl_reg *ctl;
+	struct devstate_stat_reg *stat;
+};
+
+/* These are callbacks to SOC-specific code. */
+struct dscr_ops {
+	void (*init)(struct device_node *node);
+};
+
+struct dscr_regs {
+	spinlock_t		lock;
+	void __iomem		*base;
+	u32			kick_reg[2];
+	u32			kick_key[2];
+	struct locked_reg	locked[MAX_LOCKED_REGS];
+	struct devstate_info	devstate_info[MAX_DEVSTATE_IDS];
+	struct rmii_reset_reg   rmii_resets[MAX_SOC_EMACS];
+	struct devstate_ctl_reg devctl[MAX_DEVCTL_REGS];
+	struct devstate_stat_reg devstat[MAX_DEVSTAT_REGS];
+};
+
+static struct dscr_regs	dscr;
+
+static struct locked_reg *find_locked_reg(u32 reg)
+{
+	int i;
+
+	for (i = 0; i < MAX_LOCKED_REGS; i++)
+		if (dscr.locked[i].key && reg == dscr.locked[i].reg)
+			return &dscr.locked[i];
+	return NULL;
+}
+
+/*
+ * Write to a register with one lock
+ */
+static void dscr_write_locked1(u32 reg, u32 val,
+			       u32 lock, u32 key)
+{
+	void __iomem *reg_addr = dscr.base + reg;
+	void __iomem *lock_addr = dscr.base + lock;
+
+	/*
+	 * For some registers, the lock is relocked after a short number
+	 * of cycles. We have to put the lock write and register write in
+	 * the same fetch packet to meet this timing. The .align ensures
+	 * the two stw instructions are in the same fetch packet.
+	 */
+	asm volatile ("b	.s2	0f\n"
+		      "nop	5\n"
+		      "    .align 5\n"
+		      "0:\n"
+		      "stw	.D1T2	%3,*%2\n"
+		      "stw	.D1T2	%1,*%0\n"
+		      :
+		      : "a"(reg_addr), "b"(val), "a"(lock_addr), "b"(key)
+		);
+
+	/* in case the hw doesn't reset the lock */
+	soc_writel(0, lock_addr);
+}
+
+/*
+ * Write to a register protected by two lock registers
+ */
+static void dscr_write_locked2(u32 reg, u32 val,
+			       u32 lock0, u32 key0,
+			       u32 lock1, u32 key1)
+{
+	soc_writel(key0, dscr.base + lock0);
+	soc_writel(key1, dscr.base + lock1);
+	soc_writel(val, dscr.base + reg);
+	soc_writel(0, dscr.base + lock0);
+	soc_writel(0, dscr.base + lock1);
+}
+
+static void dscr_write(u32 reg, u32 val)
+{
+	struct locked_reg *lock;
+
+	lock = find_locked_reg(reg);
+	if (lock)
+		dscr_write_locked1(reg, val, lock->lockreg, lock->key);
+	else if (dscr.kick_key[0])
+		dscr_write_locked2(reg, val, dscr.kick_reg[0], dscr.kick_key[0],
+				   dscr.kick_reg[1], dscr.kick_key[1]);
+	else
+		soc_writel(val, dscr.base + reg);
+}
+
+
+/*
+ * Drivers can use this interface to enable/disable SoC IP blocks.
+ */
+void dscr_set_devstate(int id, enum dscr_devstate_t state)
+{
+	struct devstate_ctl_reg *ctl;
+	struct devstate_stat_reg *stat;
+	struct devstate_info *info;
+	u32 ctl_val, val;
+	int ctl_shift, ctl_mask;
+	unsigned long flags;
+
+	if (!dscr.base)
+		return;
+
+	if (id < 0 || id >= MAX_DEVSTATE_IDS)
+		return;
+
+	info = &dscr.devstate_info[id];
+	ctl = info->ctl;
+	stat = info->stat;
+
+	if (ctl == NULL)
+		return;
+
+	ctl_shift = ctl->shift + ctl->nbits * (id - ctl->start_id);
+	ctl_mask = ((1 << ctl->nbits) - 1) << ctl_shift;
+
+	switch (state) {
+	case DSCR_DEVSTATE_ENABLED:
+		ctl_val = ctl->enable << ctl_shift;
+		break;
+	case DSCR_DEVSTATE_DISABLED:
+		if (ctl->enable_only)
+			return;
+		ctl_val = ctl->disable << ctl_shift;
+		break;
+	default:
+		return;
+	}
+
+	spin_lock_irqsave(&dscr.lock, flags);
+
+	val = soc_readl(dscr.base + ctl->reg);
+	val &= ~ctl_mask;
+	val |= ctl_val;
+
+	dscr_write(ctl->reg, val);
+
+	spin_unlock_irqrestore(&dscr.lock, flags);
+
+	if (!stat)
+		return;
+
+	ctl_shift = stat->shift + stat->nbits * (id - stat->start_id);
+
+	if (state == DSCR_DEVSTATE_ENABLED)
+		ctl_val = stat->enable;
+	else
+		ctl_val = stat->disable;
+
+	do {
+		val = soc_readl(dscr.base + stat->reg);
+		val >>= ctl_shift;
+		val &= ((1 << stat->nbits) - 1);
+	} while (val != ctl_val);
+}
+EXPORT_SYMBOL(dscr_set_devstate);
+
+/*
+ * Drivers can use this to reset RMII module.
+ */
+void dscr_rmii_reset(int id, int assert)
+{
+	struct rmii_reset_reg *r;
+	unsigned long flags;
+	u32 val;
+
+	if (id < 0 || id >= MAX_SOC_EMACS)
+		return;
+
+	r = &dscr.rmii_resets[id];
+	if (r->mask == 0)
+		return;
+
+	spin_lock_irqsave(&dscr.lock, flags);
+
+	val = soc_readl(dscr.base + r->reg);
+	if (assert)
+		dscr_write(r->reg, val | r->mask);
+	else
+		dscr_write(r->reg, val & ~(r->mask));
+
+	spin_unlock_irqrestore(&dscr.lock, flags);
+}
+EXPORT_SYMBOL(dscr_rmii_reset);
+
+static void __init dscr_parse_devstat(struct device_node *node,
+				      void __iomem *base)
+{
+	u32 val;
+	int err;
+
+	err = of_property_read_u32_array(node, "ti,dscr-devstat", &val, 1);
+	if (!err)
+		c6x_devstat = soc_readl(base + val);
+	printk(KERN_INFO "DEVSTAT: %08x\n", c6x_devstat);
+}
+
+static void __init dscr_parse_silicon_rev(struct device_node *node,
+					 void __iomem *base)
+{
+	u32 vals[3];
+	int err;
+
+	err = of_property_read_u32_array(node, "ti,dscr-silicon-rev", vals, 3);
+	if (!err) {
+		c6x_silicon_rev = soc_readl(base + vals[0]);
+		c6x_silicon_rev >>= vals[1];
+		c6x_silicon_rev &= vals[2];
+	}
+}
+
+/*
+ * Some SoCs will have a pair of fuse registers which hold
+ * an ethernet MAC address. The "ti,dscr-mac-fuse-regs"
+ * property is a mapping from fuse register bytes to MAC
+ * address bytes. The expected format is:
+ *
+ *	ti,dscr-mac-fuse-regs = <reg0 b3 b2 b1 b0
+ *				 reg1 b3 b2 b1 b0>
+ *
+ * reg0 and reg1 are the offsets of the two fuse registers.
+ * b3-b0 positionally represent bytes within the fuse register.
+ * b3 is the most significant byte and b0 is the least.
+ * Allowable values for b3-b0 are:
+ *
+ *	  0 = fuse register byte not used in MAC address
+ *      1-6 = index+1 into c6x_fuse_mac[]
+ */
+static void __init dscr_parse_mac_fuse(struct device_node *node,
+				       void __iomem *base)
+{
+	u32 vals[10], fuse;
+	int f, i, j, err;
+
+	err = of_property_read_u32_array(node, "ti,dscr-mac-fuse-regs",
+					 vals, 10);
+	if (err)
+		return;
+
+	for (f = 0; f < 2; f++) {
+		fuse = soc_readl(base + vals[f * 5]);
+		for (j = (f * 5) + 1, i = 24; i >= 0; i -= 8, j++)
+			if (vals[j] && vals[j] <= 6)
+				c6x_fuse_mac[vals[j] - 1] = fuse >> i;
+	}
+}
+
+static void __init dscr_parse_rmii_resets(struct device_node *node,
+					  void __iomem *base)
+{
+	const __be32 *p;
+	int i, size;
+
+	/* look for RMII reset registers */
+	p = of_get_property(node, "ti,dscr-rmii-resets", &size);
+	if (p) {
+		/* parse all the reg/mask pairs we can handle */
+		size /= (sizeof(*p) * 2);
+		if (size > MAX_SOC_EMACS)
+			size = MAX_SOC_EMACS;
+
+		for (i = 0; i < size; i++) {
+			dscr.rmii_resets[i].reg = be32_to_cpup(p++);
+			dscr.rmii_resets[i].mask = be32_to_cpup(p++);
+		}
+	}
+}
+
+
+static void __init dscr_parse_privperm(struct device_node *node,
+				       void __iomem *base)
+{
+	u32 vals[2];
+	int err;
+
+	err = of_property_read_u32_array(node, "ti,dscr-privperm", vals, 2);
+	if (err)
+		return;
+	dscr_write(vals[0], vals[1]);
+}
+
+/*
+ * SoCs may have "locked" DSCR registers which can only be written
+ * to only after writing a key value to a lock registers. These
+ * regisers can be described with the "ti,dscr-locked-regs" property.
+ * This property provides a list of register descriptions with each
+ * description consisting of three values.
+ *
+ *	ti,dscr-locked-regs = <reg0 lockreg0 key0
+ *                               ...
+ *                             regN lockregN keyN>;
+ *
+ * reg is the offset of the locked register
+ * lockreg is the offset of the lock register
+ * key is the unlock key written to lockreg
+ *
+ */
+static void __init dscr_parse_locked_regs(struct device_node *node,
+					  void __iomem *base)
+{
+	struct locked_reg *r;
+	const __be32 *p;
+	int i, size;
+
+	p = of_get_property(node, "ti,dscr-locked-regs", &size);
+	if (p) {
+		/* parse all the register descriptions we can handle */
+		size /= (sizeof(*p) * 3);
+		if (size > MAX_LOCKED_REGS)
+			size = MAX_LOCKED_REGS;
+
+		for (i = 0; i < size; i++) {
+			r = &dscr.locked[i];
+
+			r->reg = be32_to_cpup(p++);
+			r->lockreg = be32_to_cpup(p++);
+			r->key = be32_to_cpup(p++);
+		}
+	}
+}
+
+/*
+ * SoCs may have DSCR registers which are only write enabled after
+ * writing specific key values to two registers. The two key registers
+ * and the key values can be parsed from a "ti,dscr-kick-regs"
+ * propety with the following layout:
+ *
+ *	ti,dscr-kick-regs = <kickreg0 key0 kickreg1 key1>
+ *
+ * kickreg is the offset of the "kick" register
+ * key is the value which unlocks writing for protected regs
+ */
+static void __init dscr_parse_kick_regs(struct device_node *node,
+					void __iomem *base)
+{
+	u32 vals[4];
+	int err;
+
+	err = of_property_read_u32_array(node, "ti,dscr-kick-regs", vals, 4);
+	if (!err) {
+		dscr.kick_reg[0] = vals[0];
+		dscr.kick_key[0] = vals[1];
+		dscr.kick_reg[1] = vals[2];
+		dscr.kick_key[1] = vals[3];
+	}
+}
+
+
+/*
+ * SoCs may provide controls to enable/disable individual IP blocks. These
+ * controls in the DSCR usually control pin drivers but also may control
+ * clocking and or resets. The device tree is used to describe the bitfields
+ * in registers used to control device state. The number of bits and their
+ * values may vary even within the same register.
+ *
+ * The layout of these bitfields is described by the ti,dscr-devstate-ctl-regs
+ * property. This property is a list where each element describes a contiguous
+ * range of control fields with like properties. Each element of the list
+ * consists of 7 cells with the following values:
+ *
+ *   start_id num_ids reg enable disable start_bit nbits
+ *
+ * start_id is device id for the first device control in the range
+ * num_ids is the number of device controls in the range
+ * reg is the offset of the register holding the control bits
+ * enable is the value to enable a device
+ * disable is the value to disable a device (0xffffffff if cannot disable)
+ * start_bit is the bit number of the first bit in the range
+ * nbits is the number of bits per device control
+ */
+static void __init dscr_parse_devstate_ctl_regs(struct device_node *node,
+						void __iomem *base)
+{
+	struct devstate_ctl_reg *r;
+	const __be32 *p;
+	int i, j, size;
+
+	p = of_get_property(node, "ti,dscr-devstate-ctl-regs", &size);
+	if (p) {
+		/* parse all the ranges we can handle */
+		size /= (sizeof(*p) * 7);
+		if (size > MAX_DEVCTL_REGS)
+			size = MAX_DEVCTL_REGS;
+
+		for (i = 0; i < size; i++) {
+			r = &dscr.devctl[i];
+
+			r->start_id = be32_to_cpup(p++);
+			r->num_ids = be32_to_cpup(p++);
+			r->reg = be32_to_cpup(p++);
+			r->enable = be32_to_cpup(p++);
+			r->disable = be32_to_cpup(p++);
+			if (r->disable == 0xffffffff)
+				r->enable_only = 1;
+			r->shift = be32_to_cpup(p++);
+			r->nbits = be32_to_cpup(p++);
+
+			for (j = r->start_id;
+			     j < (r->start_id + r->num_ids);
+			     j++)
+				dscr.devstate_info[j].ctl = r;
+		}
+	}
+}
+
+/*
+ * SoCs may provide status registers indicating the state (enabled/disabled) of
+ * devices on the SoC. The device tree is used to describe the bitfields in
+ * registers used to provide device status. The number of bits and their
+ * values used to provide status may vary even within the same register.
+ *
+ * The layout of these bitfields is described by the ti,dscr-devstate-stat-regs
+ * property. This property is a list where each element describes a contiguous
+ * range of status fields with like properties. Each element of the list
+ * consists of 7 cells with the following values:
+ *
+ *   start_id num_ids reg enable disable start_bit nbits
+ *
+ * start_id is device id for the first device status in the range
+ * num_ids is the number of devices covered by the range
+ * reg is the offset of the register holding the status bits
+ * enable is the value indicating device is enabled
+ * disable is the value indicating device is disabled
+ * start_bit is the bit number of the first bit in the range
+ * nbits is the number of bits per device status
+ */
+static void __init dscr_parse_devstate_stat_regs(struct device_node *node,
+						 void __iomem *base)
+{
+	struct devstate_stat_reg *r;
+	const __be32 *p;
+	int i, j, size;
+
+	p = of_get_property(node, "ti,dscr-devstate-stat-regs", &size);
+	if (p) {
+		/* parse all the ranges we can handle */
+		size /= (sizeof(*p) * 7);
+		if (size > MAX_DEVSTAT_REGS)
+			size = MAX_DEVSTAT_REGS;
+
+		for (i = 0; i < size; i++) {
+			r = &dscr.devstat[i];
+
+			r->start_id = be32_to_cpup(p++);
+			r->num_ids = be32_to_cpup(p++);
+			r->reg = be32_to_cpup(p++);
+			r->enable = be32_to_cpup(p++);
+			r->disable = be32_to_cpup(p++);
+			r->shift = be32_to_cpup(p++);
+			r->nbits = be32_to_cpup(p++);
+
+			for (j = r->start_id;
+			     j < (r->start_id + r->num_ids);
+			     j++)
+				dscr.devstate_info[j].stat = r;
+		}
+	}
+}
+
+static struct of_device_id dscr_ids[] __initdata = {
+	{ .compatible = "ti,c64x+dscr" },
+	{}
+};
+
+/*
+ * Probe for DSCR area.
+ *
+ * This has to be done early on in case timer or interrupt controller
+ * needs something. e.g. On C6455 SoC, timer must be enabled through
+ * DSCR before it is functional.
+ */
+void __init dscr_probe(void)
+{
+	struct device_node *node;
+	void __iomem *base;
+
+	spin_lock_init(&dscr.lock);
+
+	node = of_find_matching_node(NULL, dscr_ids);
+	if (!node)
+		return;
+
+	base = of_iomap(node, 0);
+	if (!base) {
+		of_node_put(node);
+		return;
+	}
+
+	dscr.base = base;
+
+	dscr_parse_devstat(node, base);
+	dscr_parse_silicon_rev(node, base);
+	dscr_parse_mac_fuse(node, base);
+	dscr_parse_rmii_resets(node, base);
+	dscr_parse_locked_regs(node, base);
+	dscr_parse_kick_regs(node, base);
+	dscr_parse_devstate_ctl_regs(node, base);
+	dscr_parse_devstate_stat_regs(node, base);
+	dscr_parse_privperm(node, base);
+}