bus: add Broadcom GISB bus arbiter timeout/error handler

This patch adds support for the Broadcom GISB arbiter bus timeout/error
handler. GISB is a proprietary bus used by Broadcom Set Top Box
System-on-a-chip devices (BCM7xxx) which allows multiple masters and
clients to be interfaced with each other.

The bus arbiter offers support for generating two interrupts towards the
host CPU, thus allowing us to "catch" clock gated masters, or masters
being volontarily blocked for powersaving purposes, or do general system
troubleshooting.

We also register a hook with the ARM fault exception handling to allow
printing a more informative message than "imprecise external abort at
0x00000000" for instance.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/bus/Kconfig

@@ -4,6 +4,14 @@
 
 menu "Bus devices"
 
+config BRCMSTB_GISB_ARB
+	bool "Broadcom STB GISB bus arbiter"
+	depends on ARM
+	help
+	  Driver for the Broadcom Set Top Box System-on-a-chip internal bus
+	  arbiter. This driver provides timeout and target abort error handling
+	  and internal bus master decoding.
+
 config IMX_WEIM
 	bool "Freescale EIM DRIVER"
 	depends on ARCH_MXC

drivers/bus/Makefile

@@ -2,6 +2,7 @@
 # Makefile for the bus drivers.
 #
 
+obj-$(CONFIG_BRCMSTB_GISB_ARB)	+= brcmstb_gisb.o
 obj-$(CONFIG_IMX_WEIM)	+= imx-weim.o
 obj-$(CONFIG_MVEBU_MBUS) += mvebu-mbus.o
 obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o

drivers/bus/brcmstb_gisb.c

@@ -0,0 +1,289 @@
+/*
+ * Copyright (C) 2014 Broadcom Corporation
+ *
+ * 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.
+ *
+ * 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.
+ */
+
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/string.h>
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/of.h>
+#include <linux/bitops.h>
+
+#include <asm/bug.h>
+#include <asm/signal.h>
+
+#define ARB_TIMER			0x008
+#define ARB_ERR_CAP_CLR			0x7e4
+#define  ARB_ERR_CAP_CLEAR		(1 << 0)
+#define ARB_ERR_CAP_HI_ADDR		0x7e8
+#define ARB_ERR_CAP_ADDR		0x7ec
+#define ARB_ERR_CAP_DATA		0x7f0
+#define ARB_ERR_CAP_STATUS		0x7f4
+#define  ARB_ERR_CAP_STATUS_TIMEOUT	(1 << 12)
+#define  ARB_ERR_CAP_STATUS_TEA		(1 << 11)
+#define  ARB_ERR_CAP_STATUS_BS_SHIFT	(1 << 2)
+#define  ARB_ERR_CAP_STATUS_BS_MASK	0x3c
+#define  ARB_ERR_CAP_STATUS_WRITE	(1 << 1)
+#define  ARB_ERR_CAP_STATUS_VALID	(1 << 0)
+#define ARB_ERR_CAP_MASTER		0x7f8
+
+struct brcmstb_gisb_arb_device {
+	void __iomem	*base;
+	struct mutex	lock;
+	struct list_head next;
+	u32 valid_mask;
+	const char *master_names[sizeof(u32) * BITS_PER_BYTE];
+};
+
+static LIST_HEAD(brcmstb_gisb_arb_device_list);
+
+static ssize_t gisb_arb_get_timeout(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct brcmstb_gisb_arb_device *gdev = platform_get_drvdata(pdev);
+	u32 timeout;
+
+	mutex_lock(&gdev->lock);
+	timeout = ioread32(gdev->base + ARB_TIMER);
+	mutex_unlock(&gdev->lock);
+
+	return sprintf(buf, "%d", timeout);
+}
+
+static ssize_t gisb_arb_set_timeout(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct brcmstb_gisb_arb_device *gdev = platform_get_drvdata(pdev);
+	int val, ret;
+
+	ret = kstrtoint(buf, 10, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val == 0 || val >= 0xffffffff)
+		return -EINVAL;
+
+	mutex_lock(&gdev->lock);
+	iowrite32(val, gdev->base + ARB_TIMER);
+	mutex_unlock(&gdev->lock);
+
+	return count;
+}
+
+static const char *
+brcmstb_gisb_master_to_str(struct brcmstb_gisb_arb_device *gdev,
+						u32 masters)
+{
+	u32 mask = gdev->valid_mask & masters;
+
+	if (hweight_long(mask) != 1)
+		return NULL;
+
+	return gdev->master_names[ffs(mask) - 1];
+}
+
+static int brcmstb_gisb_arb_decode_addr(struct brcmstb_gisb_arb_device *gdev,
+					const char *reason)
+{
+	u32 cap_status;
+	unsigned long arb_addr;
+	u32 master;
+	const char *m_name;
+	char m_fmt[11];
+
+	cap_status = ioread32(gdev->base + ARB_ERR_CAP_STATUS);
+
+	/* Invalid captured address, bail out */
+	if (!(cap_status & ARB_ERR_CAP_STATUS_VALID))
+		return 1;
+
+	/* Read the address and master */
+	arb_addr = ioread32(gdev->base + ARB_ERR_CAP_ADDR) & 0xffffffff;
+#if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+	arb_addr |= (u64)ioread32(gdev->base + ARB_ERR_CAP_HI_ADDR) << 32;
+#endif
+	master = ioread32(gdev->base + ARB_ERR_CAP_MASTER);
+
+	m_name = brcmstb_gisb_master_to_str(gdev, master);
+	if (!m_name) {
+		snprintf(m_fmt, sizeof(m_fmt), "0x%08x", master);
+		m_name = m_fmt;
+	}
+
+	pr_crit("%s: %s at 0x%lx [%c %s], core: %s\n",
+		__func__, reason, arb_addr,
+		cap_status & ARB_ERR_CAP_STATUS_WRITE ? 'W' : 'R',
+		cap_status & ARB_ERR_CAP_STATUS_TIMEOUT ? "timeout" : "",
+		m_name);
+
+	/* clear the GISB error */
+	iowrite32(ARB_ERR_CAP_CLEAR, gdev->base + ARB_ERR_CAP_CLR);
+
+	return 0;
+}
+
+static int brcmstb_bus_error_handler(unsigned long addr, unsigned int fsr,
+				     struct pt_regs *regs)
+{
+	int ret = 0;
+	struct brcmstb_gisb_arb_device *gdev;
+
+	/* iterate over each GISB arb registered handlers */
+	list_for_each_entry(gdev, &brcmstb_gisb_arb_device_list, next)
+		ret |= brcmstb_gisb_arb_decode_addr(gdev, "bus error");
+	/*
+	 * If it was an imprecise abort, then we need to correct the
+	 * return address to be _after_ the instruction.
+	*/
+	if (fsr & (1 << 10))
+		regs->ARM_pc += 4;
+
+	return ret;
+}
+
+void __init brcmstb_hook_fault_code(void)
+{
+	hook_fault_code(22, brcmstb_bus_error_handler, SIGBUS, 0,
+			"imprecise external abort");
+}
+
+static irqreturn_t brcmstb_gisb_timeout_handler(int irq, void *dev_id)
+{
+	brcmstb_gisb_arb_decode_addr(dev_id, "timeout");
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t brcmstb_gisb_tea_handler(int irq, void *dev_id)
+{
+	brcmstb_gisb_arb_decode_addr(dev_id, "target abort");
+
+	return IRQ_HANDLED;
+}
+
+static DEVICE_ATTR(gisb_arb_timeout, S_IWUSR | S_IRUGO,
+		gisb_arb_get_timeout, gisb_arb_set_timeout);
+
+static struct attribute *gisb_arb_sysfs_attrs[] = {
+	&dev_attr_gisb_arb_timeout.attr,
+	NULL,
+};
+
+static struct attribute_group gisb_arb_sysfs_attr_group = {
+	.attrs = gisb_arb_sysfs_attrs,
+};
+
+static int brcmstb_gisb_arb_probe(struct platform_device *pdev)
+{
+	struct device_node *dn = pdev->dev.of_node;
+	struct brcmstb_gisb_arb_device *gdev;
+	struct resource *r;
+	int err, timeout_irq, tea_irq;
+	unsigned int num_masters, j = 0;
+	int i, first, last;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	timeout_irq = platform_get_irq(pdev, 0);
+	tea_irq = platform_get_irq(pdev, 1);
+
+	gdev = devm_kzalloc(&pdev->dev, sizeof(*gdev), GFP_KERNEL);
+	if (!gdev)
+		return -ENOMEM;
+
+	mutex_init(&gdev->lock);
+	INIT_LIST_HEAD(&gdev->next);
+
+	gdev->base = devm_request_and_ioremap(&pdev->dev, r);
+	if (!gdev->base)
+		return -ENOMEM;
+
+	err = devm_request_irq(&pdev->dev, timeout_irq,
+				brcmstb_gisb_timeout_handler, 0, pdev->name,
+				gdev);
+	if (err < 0)
+		return err;
+
+	err = devm_request_irq(&pdev->dev, tea_irq,
+				brcmstb_gisb_tea_handler, 0, pdev->name,
+				gdev);
+	if (err < 0)
+		return err;
+
+	/* If we do not have a valid mask, assume all masters are enabled */
+	if (of_property_read_u32(dn, "brcm,gisb-arb-master-mask",
+				&gdev->valid_mask))
+		gdev->valid_mask = 0xffffffff;
+
+	/* Proceed with reading the litteral names if we agree on the
+	 * number of masters
+	 */
+	num_masters = of_property_count_strings(dn,
+			"brcm,gisb-arb-master-names");
+	if (hweight_long(gdev->valid_mask) == num_masters) {
+		first = ffs(gdev->valid_mask) - 1;
+		last = fls(gdev->valid_mask) - 1;
+
+		for (i = first; i < last; i++) {
+			if (!(gdev->valid_mask & BIT(i)))
+				continue;
+
+			of_property_read_string_index(dn,
+					"brcm,gisb-arb-master-names", j,
+					&gdev->master_names[i]);
+			j++;
+		}
+	}
+
+	err = sysfs_create_group(&pdev->dev.kobj, &gisb_arb_sysfs_attr_group);
+	if (err)
+		return err;
+
+	platform_set_drvdata(pdev, gdev);
+
+	list_add_tail(&gdev->next, &brcmstb_gisb_arb_device_list);
+
+	dev_info(&pdev->dev, "registered mem: %p, irqs: %d, %d\n",
+			gdev->base, timeout_irq, tea_irq);
+
+	return 0;
+}
+
+static const struct of_device_id brcmstb_gisb_arb_of_match[] = {
+	{ .compatible = "brcm,gisb-arb" },
+	{ },
+};
+
+static struct platform_driver brcmstb_gisb_arb_driver = {
+	.probe	= brcmstb_gisb_arb_probe,
+	.driver = {
+		.name	= "brcm-gisb-arb",
+		.owner	= THIS_MODULE,
+		.of_match_table = brcmstb_gisb_arb_of_match,
+	},
+};
+
+static int __init brcm_gisb_driver_init(void)
+{
+	return platform_driver_register(&brcmstb_gisb_arb_driver);
+}
+
+module_init(brcm_gisb_driver_init);