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Subject[PATCH 5/6] soc: bt1: Add Baikal-T1 APB-bus EHB driver
Date
From: Serge Semin <Sergey.Semin@baikalelectronics.ru>

APB-bus is the system configuration bus utilized to access the peripheral
IP-cores configuration registers space. Baikal-T1 SoC provides a way to
detect the bus protocol errors and report a short info about it by means of
the APB-bus Errors Handler Block (APB EHB). In case if an attempted APB
transaction stays with no response for a pre-defined time an interrupt
occurs and the bus gets freed for a next operation. This driver provides
the interrupt handler to detect the erroneous address, prints an error
message about the faulty address, updates an errors counter. The counter
and the APB-bus operations timeout can be accessed via corresponding sysfs
nodes. A dedicated sysfs-node can be also used to artificially cause the
bus errors described above.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Olof Johansson <olof@lixom.net>
Cc: soc@kernel.org
---
drivers/soc/baikal-t1/Kconfig | 15 ++
drivers/soc/baikal-t1/Makefile | 1 +
drivers/soc/baikal-t1/apb-ehb.c | 381 ++++++++++++++++++++++++++++++++
3 files changed, 397 insertions(+)
create mode 100644 drivers/soc/baikal-t1/apb-ehb.c

diff --git a/drivers/soc/baikal-t1/Kconfig b/drivers/soc/baikal-t1/Kconfig
index aca155350612..a021abea102f 100644
--- a/drivers/soc/baikal-t1/Kconfig
+++ b/drivers/soc/baikal-t1/Kconfig
@@ -19,4 +19,19 @@ config BT1_AXI_EHB

If unsure, say N.

+config BT1_APB_EHB
+ bool "Baikal-T1 APB-bus Errors Handler Block"
+ depends on SOC_BAIKAL_T1 && OF
+ help
+ Baikal-T1 APB-bus is used to access the IP-core blocks CSRs. In case
+ if an attempted APB transaction stays with no response for a pre-
+ defined time an interrupt occurs and the bus gets freed for a next
+ operation. It is done by the APB-bus Errors Handler Block (APB EHB).
+ This driver provides the interrupt handler to detect the erroneous
+ address, prints an error message about the address fault, updates an
+ errors counter. The counter and the APB-bus operations timeout can be
+ accessed via corresponding sysfs nodes.
+
+ If unsure, say N.
+
endmenu
diff --git a/drivers/soc/baikal-t1/Makefile b/drivers/soc/baikal-t1/Makefile
index c069791058b9..ffb035600e01 100644
--- a/drivers/soc/baikal-t1/Makefile
+++ b/drivers/soc/baikal-t1/Makefile
@@ -1,2 +1,3 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_BT1_AXI_EHB) += axi-ehb.o
+obj-$(CONFIG_BT1_APB_EHB) += apb-ehb.o
diff --git a/drivers/soc/baikal-t1/apb-ehb.c b/drivers/soc/baikal-t1/apb-ehb.c
new file mode 100644
index 000000000000..726cb75d29cb
--- /dev/null
+++ b/drivers/soc/baikal-t1/apb-ehb.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2014 - 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Authors:
+ * Serge Semin <Sergey.Semin@baikalelectronics.ru>
+ *
+ * Baikal-T1 APB-bus Errors Handler Block driver.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/atomic.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/nmi.h>
+#include <linux/time64.h>
+#include <linux/clk.h>
+#include <linux/sysfs.h>
+
+#include "common.h"
+
+#define APB_EHB_ISR 0x00
+#define APB_EHB_ISR_PENDING BIT(0)
+#define APB_EHB_ISR_MASK BIT(1)
+#define APB_EHB_ADDR 0x04
+#define APB_EHB_TIMEOUT 0x08
+
+#define APB_EHB_TIMEOUT_MIN 0x000003FFU
+#define APB_EHB_TIMEOUT_MAX 0xFFFFFFFFU
+
+#define APB_EHB_N_TO_TOUT_US(_rate, _n) ({ \
+ uint64_t _tmp = USEC_PER_SEC * (uint64_t)(_n); \
+ do_div(_tmp, _rate); \
+ _tmp; \
+})
+#define APB_EHB_TOUT_TO_N_US(_rate, _tout) ({ \
+ uint64_t _tmp = (_tout) * (uint64_t)(_rate); \
+ do_div(_tmp, USEC_PER_SEC); \
+ _tmp; \
+})
+
+/*
+ * struct apb_ehb - Baikal-T1 APB EHB private data.
+ * @dev: Pointer to the device structure.
+ * @regs: Memory mapped block registers.
+ * @reg_isr_lock: Registers memory lock.
+ * @res: No-device error injection memory region.
+ * @irq: Errors IRQ number.
+ * @count: Number of errors detected.
+ * @ref: APB-reference clock.
+ */
+struct apb_ehb {
+ struct device *dev;
+
+ void __iomem *regs;
+ spinlock_t reg_isr_lock;
+ void __iomem *res;
+ int irq;
+
+ atomic_t count;
+
+ struct clk *ref;
+};
+
+static irqreturn_t apb_ehb_isr(int irq, void *data)
+{
+ struct apb_ehb *ehb = data;
+ unsigned long flags;
+ u32 addr;
+
+ addr = bt1_read(ehb->regs + APB_EHB_ADDR);
+
+ dev_crit_ratelimited(ehb->dev,
+ "APB-bus fault %d: Slave access timeout at 0x%08x\n",
+ atomic_inc_return(&ehb->count),
+ addr);
+
+ /*
+ * Print backtrace on each CPU. This might be pointless if the fault
+ * has happened on the same CPU as the IRQ handler is executed or
+ * the other core proceeded further execution despite the error.
+ * But if it's not, by looking at the trace we would get straight to
+ * the cause of the problem.
+ */
+ trigger_all_cpu_backtrace();
+
+ spin_lock_irqsave(&ehb->reg_isr_lock, flags);
+ bt1_update(ehb->regs + APB_EHB_ISR, APB_EHB_ISR_PENDING, 0);
+ spin_unlock_irqrestore(&ehb->reg_isr_lock, flags);
+
+ return IRQ_HANDLED;
+}
+
+static void apb_ehb_clear_data(void *data)
+{
+ struct apb_ehb *ehb = data;
+ struct platform_device *pdev = to_platform_device(ehb->dev);
+
+ platform_set_drvdata(pdev, NULL);
+}
+
+static struct apb_ehb *apb_ehb_create_data(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct apb_ehb *ehb;
+ int ret;
+
+ ehb = devm_kzalloc(dev, sizeof(*ehb), GFP_KERNEL);
+ if (!ehb)
+ return ERR_PTR(-ENOMEM);
+
+ ret = devm_add_action(dev, apb_ehb_clear_data, ehb);
+ if (ret) {
+ dev_err(dev, "Can't add APB EHB data clear action\n");
+ return ERR_PTR(ret);
+ }
+
+ ehb->dev = dev;
+ atomic_set(&ehb->count, 0);
+ platform_set_drvdata(pdev, ehb);
+
+ return ehb;
+}
+
+static int apb_ehb_request_regs(struct apb_ehb *ehb)
+{
+ struct platform_device *pdev = to_platform_device(ehb->dev);
+
+ ehb->regs = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(ehb->regs)) {
+ dev_err(ehb->dev, "Couldn't map APB EHB registers\n");
+ return PTR_ERR(ehb->regs);
+ }
+
+ ehb->res = devm_platform_ioremap_resource(pdev, 1);
+ if (IS_ERR(ehb->regs)) {
+ dev_err(ehb->dev, "Couldn't map reserved region\n");
+ return PTR_ERR(ehb->res);
+ }
+
+ return 0;
+}
+
+static void apb_ehb_disable_clk(void *data)
+{
+ struct apb_ehb *ehb = data;
+
+ clk_disable_unprepare(ehb->ref);
+}
+
+static int apb_ehb_request_clk(struct apb_ehb *ehb)
+{
+ int ret;
+
+ ehb->ref = devm_clk_get(ehb->dev, "ref");
+ if (IS_ERR(ehb->ref)) {
+ dev_err(ehb->dev, "Couldn't get APB clock descriptor\n");
+ return PTR_ERR(ehb->ref);
+ }
+
+ ret = clk_prepare_enable(ehb->ref);
+ if (ret) {
+ dev_err(ehb->dev, "Couldn't enable the APB clock\n");
+ return ret;
+ }
+
+ ret = devm_add_action_or_reset(ehb->dev, apb_ehb_disable_clk, ehb);
+ if (ret)
+ dev_err(ehb->dev, "Can't add APB EHB clocks disable action\n");
+
+ return ret;
+}
+
+static void apb_ehb_clear_irq(void *data)
+{
+ struct apb_ehb *ehb = data;
+ unsigned long flags;
+
+ spin_lock_irqsave(&ehb->reg_isr_lock, flags);
+ bt1_update(ehb->regs + APB_EHB_ISR, APB_EHB_ISR_MASK, 0);
+ spin_unlock_irqrestore(&ehb->reg_isr_lock, flags);
+}
+
+static int apb_ehb_request_irq(struct apb_ehb *ehb)
+{
+ struct platform_device *pdev = to_platform_device(ehb->dev);
+ int ret;
+
+ spin_lock_init(&ehb->reg_isr_lock);
+
+ ehb->irq = platform_get_irq(pdev, 0);
+ if (ehb->irq < 0) {
+ dev_err(ehb->dev, "Couldn't find APB EHB IRQ number\n");
+ return ehb->irq;
+ }
+
+ ret = devm_request_irq(ehb->dev, ehb->irq, apb_ehb_isr, IRQF_SHARED,
+ "apb_ehb", ehb);
+ if (ret) {
+ dev_err(ehb->dev, "Couldn't request APB EHB IRQ\n");
+ return ret;
+ }
+
+ ret = devm_add_action(ehb->dev, apb_ehb_clear_irq, ehb);
+ if (ret) {
+ dev_err(ehb->dev, "Can't add APB EHB IRQs clear action\n");
+ return ret;
+ }
+
+ /* Unmask IRQ and clear it' pending flag. */
+ bt1_update(ehb->regs + APB_EHB_ISR,
+ APB_EHB_ISR_PENDING | APB_EHB_ISR_MASK, APB_EHB_ISR_MASK);
+
+ return 0;
+}
+
+static ssize_t count_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct apb_ehb *ehb = dev_get_drvdata(dev);
+
+ return scnprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&ehb->count));
+}
+static DEVICE_ATTR_RO(count);
+
+static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct apb_ehb *ehb = dev_get_drvdata(dev);
+ unsigned long timeout, rate;
+ u32 n;
+
+ rate = clk_get_rate(ehb->ref);
+ if (!rate)
+ return -ENODEV;
+
+ n = bt1_read(ehb->regs + APB_EHB_TIMEOUT);
+ timeout = APB_EHB_N_TO_TOUT_US(rate, n);
+
+ return scnprintf(buf, PAGE_SIZE, "%lu\n", timeout);
+}
+
+static ssize_t timeout_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct apb_ehb *ehb = dev_get_drvdata(dev);
+ unsigned long timeout, rate;
+ u32 n;
+
+ if (kstrtoul(buf, 0, &timeout) < 0)
+ return -EINVAL;
+
+ rate = clk_get_rate(ehb->ref);
+ if (!rate)
+ return -ENODEV;
+
+ n = APB_EHB_TOUT_TO_N_US(rate, timeout);
+ n = clamp(n, APB_EHB_TIMEOUT_MIN, APB_EHB_TIMEOUT_MAX);
+
+ bt1_write(ehb->regs + APB_EHB_TIMEOUT, n);
+
+ return count;
+}
+static DEVICE_ATTR_RW(timeout);
+
+static int inject_error_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "Error injection: nodev irq\n");
+}
+
+static int inject_error_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *data, size_t count)
+{
+ struct apb_ehb *ehb = dev_get_drvdata(dev);
+ unsigned long flags;
+
+ /*
+ * Either dummy read from the unmapped address in the APB IO area
+ * or manually set the IRQ status.
+ */
+ if (!strncmp(data, "nodev", 5)) {
+ readl(ehb->res);
+ } else if (!strncmp(data, "irq", 3)) {
+ spin_lock_irqsave(&ehb->reg_isr_lock, flags);
+ bt1_write(ehb->regs + APB_EHB_ISR,
+ APB_EHB_ISR_PENDING | APB_EHB_ISR_MASK);
+ spin_unlock_irqrestore(&ehb->reg_isr_lock, flags);
+ } else
+ return -EINVAL;
+
+ return count;
+}
+static DEVICE_ATTR_RW(inject_error);
+
+static struct attribute *apb_ehb_sysfs_attrs[] = {
+ &dev_attr_count.attr,
+ &dev_attr_timeout.attr,
+ &dev_attr_inject_error.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(apb_ehb_sysfs);
+
+static void apb_ehb_remove_sysfs(void *data)
+{
+ struct apb_ehb *ehb = data;
+
+ device_remove_groups(ehb->dev, apb_ehb_sysfs_groups);
+}
+
+static int apb_ehb_init_sysfs(struct apb_ehb *ehb)
+{
+ int ret;
+
+ ret = device_add_groups(ehb->dev, apb_ehb_sysfs_groups);
+ if (ret) {
+ dev_err(ehb->dev, "Failed to create EHB APB sysfs nodes\n");
+ return ret;
+ }
+
+ ret = devm_add_action_or_reset(ehb->dev, apb_ehb_remove_sysfs, ehb);
+ if (ret)
+ dev_err(ehb->dev, "Can't add APB EHB sysfs remove action\n");
+
+ return ret;
+}
+
+static int apb_ehb_probe(struct platform_device *pdev)
+{
+ struct apb_ehb *ehb;
+ int ret;
+
+ ehb = apb_ehb_create_data(pdev);
+ if (IS_ERR(ehb))
+ return PTR_ERR(ehb);
+
+ ret = apb_ehb_request_regs(ehb);
+ if (ret)
+ return ret;
+
+ ret = apb_ehb_request_clk(ehb);
+ if (ret)
+ return ret;
+
+ ret = apb_ehb_request_irq(ehb);
+ if (ret)
+ return ret;
+
+ ret = apb_ehb_init_sysfs(ehb);
+ if (ret)
+ return ret;
+
+ dev_info(ehb->dev, "APB-bus errors handler installed\n");
+
+ return 0;
+}
+
+static const struct of_device_id apb_ehb_of_match[] = {
+ { .compatible = "be,bt1-apb-ehb" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, apb_ehb_of_match);
+
+static struct platform_driver apb_ehb_driver = {
+ .probe = apb_ehb_probe,
+ .driver = {
+ .name = "bt1-apb-ehb",
+ .of_match_table = of_match_ptr(apb_ehb_of_match)
+ }
+};
+module_platform_driver(apb_ehb_driver);
+
+MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");
+MODULE_DESCRIPTION("Baikal-T1 APB EHB driver");
+MODULE_LICENSE("GPL v2");
--
2.25.1
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