drivers/staging: Gasket driver framework + Apex driver

The Gasket (Google ASIC Software, Kernel Extensions, and Tools) kernel
framework is a generic, flexible system that supports thin kernel
drivers. Gasket kernel drivers are expected to handle opening and
closing devices, mmap'ing BAR space as requested, a small selection of
ioctls, and handling page table translation (covered below). Any other
functions should be handled by userspace code.

The Gasket common module is not enough to run a device. In order to
customize the Gasket code for a given piece of hardware, a device
specific module must be created. At a minimum, this module must define a
struct gasket_driver_desc containing the device-specific data for use by
the framework; in addition, the module must declare an __init function
that calls gasket_register_device with the module's gasket_driver_desc
struct. Finally, the driver must define an exit function that calls
gasket_unregister_device with the module's gasket_driver_desc struct.

One of the core assumptions of the Gasket framework is that precisely
one process is allowed to have an open write handle to the device node
at any given time. (That process may, once it has one write handle, open
any number of additional write handles.) This is accomplished by
tracking open and close data for each driver instance.

Signed-off-by: Rob Springer <rspringer@google.com>
Signed-off-by: John Joseph <jnjoseph@google.com>
Signed-off-by: Simon Que <sque@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 638 insertions, 0 deletions

diff --git a/drivers/staging/gasket/gasket_interrupt.c b/drivers/staging/gasket/gasket_interrupt.c
new file mode 100644
index 000000000000..b74eefe41d72
--- /dev/null
+++ b/drivers/staging/gasket/gasket_interrupt.c
@@ -0,0 +1,638 @@
+/* Copyright (C) 2018 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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 "gasket_interrupt.h"
+
+#include "gasket_constants.h"
+#include "gasket_core.h"
+#include "gasket_logging.h"
+#include "gasket_sysfs.h"
+#include <linux/interrupt.h>
+#include <linux/version.h>
+#ifdef GASKET_KERNEL_TRACE_SUPPORT
+#define CREATE_TRACE_POINTS
+#include <trace/events/gasket_interrupt.h>
+#else
+#define trace_gasket_interrupt_event(x, ...)
+#endif
+/* Retry attempts if the requested number of interrupts aren't available. */
+#define MSIX_RETRY_COUNT 3
+
+/* Instance interrupt management data. */
+struct gasket_interrupt_data {
+	/* The name associated with this interrupt data. */
+	const char *name;
+
+	/* Interrupt type. See gasket_interrupt_type in gasket_core.h */
+	int type;
+
+	/* The PCI device [if any] associated with the owning device. */
+	struct pci_dev *pci_dev;
+
+	/* Set to 1 if MSI-X has successfully been configred, 0 otherwise. */
+	int msix_configured;
+
+	/* The number of interrupts requested by the owning device. */
+	int num_interrupts;
+
+	/* A pointer to the interrupt descriptor struct for this device. */
+	const struct gasket_interrupt_desc *interrupts;
+
+	/* The index of the bar into which interrupts should be mapped. */
+	int interrupt_bar_index;
+
+	/* The width of a single interrupt in a packed interrupt register. */
+	int pack_width;
+
+	/* offset of wire interrupt registers */
+	const struct gasket_wire_interrupt_offsets *wire_interrupt_offsets;
+
+	/*
+	 * Design-wise, these elements should be bundled together, but
+	 * pci_enable_msix's interface requires that they be managed
+	 * individually (requires array of struct msix_entry).
+	 */
+
+	/* The number of successfully configured interrupts. */
+	int num_configured;
+
+	/* The MSI-X data for each requested/configured interrupt. */
+	struct msix_entry *msix_entries;
+
+	/* The eventfd "callback" data for each interrupt. */
+	struct eventfd_ctx **eventfd_ctxs;
+
+	/* The number of times each interrupt has been called. */
+	ulong *interrupt_counts;
+
+	/* Linux IRQ number. */
+	int irq;
+};
+
+/* Function definitions. */
+static ssize_t interrupt_sysfs_show(
+	struct device *device, struct device_attribute *attr, char *buf);
+
+static irqreturn_t gasket_msix_interrupt_handler(int irq, void *dev_id);
+
+/* Structures to display interrupt counts in sysfs. */
+enum interrupt_sysfs_attribute_type {
+	ATTR_INTERRUPT_COUNTS,
+};
+
+static struct gasket_sysfs_attribute interrupt_sysfs_attrs[] = {
+	GASKET_SYSFS_RO(
+		interrupt_counts, interrupt_sysfs_show, ATTR_INTERRUPT_COUNTS),
+	GASKET_END_OF_ATTR_ARRAY,
+};
+
+/*
+ * Set up device registers for interrupt handling.
+ * @gasket_dev: The Gasket information structure for this device.
+ *
+ * Sets up the device registers with the correct indices for the relevant
+ * interrupts.
+ */
+static void gasket_interrupt_setup(struct gasket_dev *gasket_dev);
+
+/* MSIX init and cleanup. */
+static int gasket_interrupt_msix_init(
+	struct gasket_interrupt_data *interrupt_data);
+static void gasket_interrupt_msix_cleanup(
+	struct gasket_interrupt_data *interrupt_data);
+static void force_msix_interrupt_unmasking(struct gasket_dev *gasket_dev);
+
+int gasket_interrupt_init(
+	struct gasket_dev *gasket_dev, const char *name, int type,
+	const struct gasket_interrupt_desc *interrupts,
+	int num_interrupts, int pack_width, int bar_index,
+	const struct gasket_wire_interrupt_offsets *wire_int_offsets)
+{
+	int ret;
+	struct gasket_interrupt_data *interrupt_data;
+
+	interrupt_data = kzalloc(
+		sizeof(struct gasket_interrupt_data), GFP_KERNEL);
+	if (!interrupt_data)
+		return -ENOMEM;
+	gasket_dev->interrupt_data = interrupt_data;
+	interrupt_data->name = name;
+	interrupt_data->type = type;
+	interrupt_data->pci_dev = gasket_dev->pci_dev;
+	interrupt_data->num_interrupts = num_interrupts;
+	interrupt_data->interrupts = interrupts;
+	interrupt_data->interrupt_bar_index = bar_index;
+	interrupt_data->pack_width = pack_width;
+	interrupt_data->num_configured = 0;
+	interrupt_data->wire_interrupt_offsets = wire_int_offsets;
+
+	/* Allocate all dynamic structures. */
+	interrupt_data->msix_entries = kzalloc(
+		sizeof(struct msix_entry) * num_interrupts, GFP_KERNEL);
+	if (!interrupt_data->msix_entries) {
+		kfree(interrupt_data);
+		return -ENOMEM;
+	}
+
+	interrupt_data->eventfd_ctxs = kzalloc(
+		sizeof(struct eventfd_ctx *) * num_interrupts, GFP_KERNEL);
+	if (!interrupt_data->eventfd_ctxs) {
+		kfree(interrupt_data->msix_entries);
+		kfree(interrupt_data);
+		return -ENOMEM;
+	}
+
+	interrupt_data->interrupt_counts = kzalloc(
+		sizeof(ulong) * num_interrupts, GFP_KERNEL);
+	if (!interrupt_data->interrupt_counts) {
+		kfree(interrupt_data->eventfd_ctxs);
+		kfree(interrupt_data->msix_entries);
+		kfree(interrupt_data);
+		return -ENOMEM;
+	}
+
+	switch (interrupt_data->type) {
+	case PCI_MSIX:
+		ret = gasket_interrupt_msix_init(interrupt_data);
+		if (ret)
+			break;
+		force_msix_interrupt_unmasking(gasket_dev);
+		break;
+
+	case PCI_MSI:
+	case PLATFORM_WIRE:
+	default:
+		gasket_nodev_error(
+			"Cannot handle unsupported interrupt type %d.",
+			interrupt_data->type);
+		ret = -EINVAL;
+	};
+
+	if (ret) {
+		/* Failing to setup interrupts will cause the device to report
+		 * GASKET_STATUS_LAMED. But it is not fatal.
+		 */
+		gasket_log_warn(
+			gasket_dev, "Couldn't initialize interrupts: %d", ret);
+		return 0;
+	}
+
+	gasket_interrupt_setup(gasket_dev);
+	gasket_sysfs_create_entries(
+		gasket_dev->dev_info.device, interrupt_sysfs_attrs);
+
+	return 0;
+}
+
+static int gasket_interrupt_msix_init(
+	struct gasket_interrupt_data *interrupt_data)
+{
+	int ret = 1;
+	int i;
+
+	for (i = 0; i < interrupt_data->num_interrupts; i++) {
+		interrupt_data->msix_entries[i].entry = i;
+		interrupt_data->msix_entries[i].vector = 0;
+		interrupt_data->eventfd_ctxs[i] = NULL;
+	}
+
+	/* Retry MSIX_RETRY_COUNT times if not enough IRQs are available. */
+	for (i = 0; i < MSIX_RETRY_COUNT && ret > 0; i++)
+		ret = pci_enable_msix_exact(interrupt_data->pci_dev,
+					    interrupt_data->msix_entries,
+					    interrupt_data->num_interrupts);
+
+	if (ret)
+		return ret > 0 ? -EBUSY : ret;
+	interrupt_data->msix_configured = 1;
+
+	for (i = 0; i < interrupt_data->num_interrupts; i++) {
+		ret = request_irq(
+			interrupt_data->msix_entries[i].vector,
+			gasket_msix_interrupt_handler, 0, interrupt_data->name,
+			interrupt_data);
+
+		if (ret) {
+			gasket_nodev_error(
+				"Cannot get IRQ for interrupt %d, vector %d; "
+				"%d\n",
+				i, interrupt_data->msix_entries[i].vector, ret);
+			return ret;
+		}
+
+		interrupt_data->num_configured++;
+	}
+
+	return 0;
+}
+
+static void gasket_interrupt_msix_cleanup(
+	struct gasket_interrupt_data *interrupt_data)
+{
+	int i;
+
+	for (i = 0; i < interrupt_data->num_configured; i++)
+		free_irq(interrupt_data->msix_entries[i].vector,
+			 interrupt_data);
+	interrupt_data->num_configured = 0;
+
+	if (interrupt_data->msix_configured)
+		pci_disable_msix(interrupt_data->pci_dev);
+	interrupt_data->msix_configured = 0;
+}
+
+/*
+ * On QCM DragonBoard, we exit gasket_interrupt_msix_init() and kernel interrupt
+ * setup code with MSIX vectors masked. This is wrong because nothing else in
+ * the driver will normally touch the MSIX vectors.
+ *
+ * As a temporary hack, force unmasking there.
+ *
+ * TODO: Figure out why QCM kernel doesn't unmask the MSIX vectors, after
+ * gasket_interrupt_msix_init(), and remove this code.
+ */
+static void force_msix_interrupt_unmasking(struct gasket_dev *gasket_dev)
+{
+	int i;
+#define MSIX_VECTOR_SIZE 16
+#define MSIX_MASK_BIT_OFFSET 12
+#define APEX_BAR2_REG_KERNEL_HIB_MSIX_TABLE 0x46800
+	for (i = 0; i < gasket_dev->interrupt_data->num_configured; i++) {
+		/* Check if the MSIX vector is unmasked */
+		ulong location = APEX_BAR2_REG_KERNEL_HIB_MSIX_TABLE +
+				 MSIX_MASK_BIT_OFFSET + i * MSIX_VECTOR_SIZE;
+		u32 mask =
+			gasket_dev_read_32(
+				gasket_dev,
+				gasket_dev->interrupt_data->interrupt_bar_index,
+				location);
+		if (!(mask & 1))
+			continue;
+		/* Unmask the msix vector (clear 32 bits) */
+		gasket_dev_write_32(
+			gasket_dev, 0,
+			gasket_dev->interrupt_data->interrupt_bar_index,
+			location);
+	}
+#undef MSIX_VECTOR_SIZE
+#undef MSIX_MASK_BIT_OFFSET
+#undef APEX_BAR2_REG_KERNEL_HIB_MSIX_TABLE
+}
+
+int gasket_interrupt_reinit(struct gasket_dev *gasket_dev)
+{
+	int ret;
+
+	if (!gasket_dev->interrupt_data) {
+		gasket_log_error(
+			gasket_dev,
+			"Attempted to reinit uninitialized interrupt data.");
+		return -EINVAL;
+	}
+
+	switch (gasket_dev->interrupt_data->type) {
+	case PCI_MSIX:
+		gasket_interrupt_msix_cleanup(gasket_dev->interrupt_data);
+		ret = gasket_interrupt_msix_init(gasket_dev->interrupt_data);
+		if (ret)
+			break;
+		force_msix_interrupt_unmasking(gasket_dev);
+		break;
+
+	case PCI_MSI:
+	case PLATFORM_WIRE:
+	default:
+		gasket_nodev_error(
+			"Cannot handle unsupported interrupt type %d.",
+			gasket_dev->interrupt_data->type);
+		ret = -EINVAL;
+	};
+
+	if (ret) {
+		/* Failing to setup MSIx will cause the device
+		 * to report GASKET_STATUS_LAMED, but is not fatal.
+		 */
+		gasket_log_warn(gasket_dev, "Couldn't init msix: %d", ret);
+		return 0;
+	}
+
+	gasket_interrupt_setup(gasket_dev);
+
+	return 0;
+}
+
+/* See gasket_interrupt.h for description. */
+int gasket_interrupt_reset_counts(struct gasket_dev *gasket_dev)
+{
+	gasket_log_debug(gasket_dev, "Clearing interrupt counts.");
+	memset(gasket_dev->interrupt_data->interrupt_counts, 0,
+	       gasket_dev->interrupt_data->num_interrupts *
+			sizeof(*gasket_dev->interrupt_data->interrupt_counts));
+	return 0;
+}
+
+/*
+ * Set up device registers for interrupt handling.
+ * @gasket_dev: The Gasket information structure for this device.
+ *
+ * Sets up the device registers with the correct indices for the relevant
+ * interrupts.
+ */
+static void gasket_interrupt_setup(struct gasket_dev *gasket_dev)
+{
+	int i;
+	int pack_shift;
+	ulong mask;
+	ulong value;
+	struct gasket_interrupt_data *interrupt_data =
+		gasket_dev->interrupt_data;
+
+	if (!interrupt_data) {
+		gasket_log_error(
+			gasket_dev, "Interrupt data is not initialized.");
+		return;
+	}
+
+	gasket_log_debug(gasket_dev, "Running interrupt setup.");
+
+	if (interrupt_data->type == PLATFORM_WIRE ||
+	    interrupt_data->type == PCI_MSI) {
+		/* Nothing needs to be done for platform or PCI devices. */
+		return;
+	}
+
+	if (interrupt_data->type != PCI_MSIX) {
+		gasket_nodev_error(
+			"Cannot handle unsupported interrupt type %d.",
+			interrupt_data->type);
+		return;
+	}
+
+	/* Setup the MSIX table. */
+
+	for (i = 0; i < interrupt_data->num_interrupts; i++) {
+		/*
+		 * If the interrupt is not packed, we can write the index into
+		 * the register directly. If not, we need to deal with a read-
+		 * modify-write and shift based on the packing index.
+		 */
+		gasket_log_debug(
+			gasket_dev,
+			"Setting up interrupt index %d with index 0x%llx and "
+			"packing %d",
+			interrupt_data->interrupts[i].index,
+			interrupt_data->interrupts[i].reg,
+			interrupt_data->interrupts[i].packing);
+		if (interrupt_data->interrupts[i].packing == UNPACKED) {
+			value = interrupt_data->interrupts[i].index;
+		} else {
+			switch (interrupt_data->interrupts[i].packing) {
+			case PACK_0:
+				pack_shift = 0;
+				break;
+			case PACK_1:
+				pack_shift = interrupt_data->pack_width;
+				break;
+			case PACK_2:
+				pack_shift = 2 * interrupt_data->pack_width;
+				break;
+			case PACK_3:
+				pack_shift = 3 * interrupt_data->pack_width;
+				break;
+			default:
+				gasket_nodev_error(
+					"Found interrupt description with "
+					"unknown enum %d.",
+					interrupt_data->interrupts[i].packing);
+				return;
+			}
+
+			mask = ~(0xFFFF << pack_shift);
+			value = gasket_dev_read_64(
+					gasket_dev,
+					interrupt_data->interrupt_bar_index,
+					interrupt_data->interrupts[i].reg) &
+				mask;
+			value |= interrupt_data->interrupts[i].index
+				 << pack_shift;
+		}
+		gasket_dev_write_64(gasket_dev, value,
+				    interrupt_data->interrupt_bar_index,
+				    interrupt_data->interrupts[i].reg);
+	}
+}
+
+/* See gasket_interrupt.h for description. */
+void gasket_interrupt_pause(struct gasket_dev *gasket_dev, int enable_pause)
+{
+	WARN_ON(!gasket_dev);
+
+	if (!gasket_dev->interrupt_data)
+		return; /* nothing to do */
+
+	if (gasket_dev->interrupt_data->type == PCI_MSI ||
+	    gasket_dev->interrupt_data->type == PCI_MSIX) {
+		/* Nothing to be done for MSI/MSIX just yet. */
+	}
+
+	if (gasket_dev->interrupt_data->type == PLATFORM_WIRE) {
+		/* Nothing to be done for PLATFORM_WIRE */
+	}
+}
+EXPORT_SYMBOL(gasket_interrupt_pause);
+
+void gasket_interrupt_cleanup(struct gasket_dev *gasket_dev)
+{
+	struct gasket_interrupt_data *interrupt_data =
+		gasket_dev->interrupt_data;
+	/*
+	 * It is possible to get an error code from gasket_interrupt_init
+	 * before interrupt_data has been allocated, so check it.
+	 */
+	if (!interrupt_data)
+		return;
+
+	switch (interrupt_data->type) {
+	case PCI_MSIX:
+		gasket_interrupt_msix_cleanup(interrupt_data);
+		break;
+
+	case PCI_MSI:
+	case PLATFORM_WIRE:
+	default:
+		gasket_nodev_error(
+			"Cannot handle unsupported interrupt type %d.",
+			interrupt_data->type);
+	};
+
+	kfree(interrupt_data->interrupt_counts);
+	kfree(interrupt_data->eventfd_ctxs);
+	kfree(interrupt_data->msix_entries);
+	kfree(interrupt_data);
+	gasket_dev->interrupt_data = NULL;
+}
+
+int gasket_interrupt_system_status(struct gasket_dev *gasket_dev)
+{
+	if (!gasket_dev->interrupt_data) {
+		gasket_nodev_info("Interrupt data is null.");
+		return GASKET_STATUS_DEAD;
+	}
+
+	if (!gasket_dev->interrupt_data->msix_configured) {
+		gasket_nodev_info("Interrupt not initialized.");
+		return GASKET_STATUS_LAMED;
+	}
+
+	if (gasket_dev->interrupt_data->num_configured !=
+		gasket_dev->interrupt_data->num_interrupts) {
+		gasket_nodev_info("Not all interrupts were configured.");
+		return GASKET_STATUS_LAMED;
+	}
+
+	return GASKET_STATUS_ALIVE;
+}
+
+int gasket_interrupt_set_eventfd(
+	struct gasket_interrupt_data *interrupt_data, int interrupt,
+	int event_fd)
+{
+	struct eventfd_ctx *ctx = eventfd_ctx_fdget(event_fd);
+
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+
+	if (interrupt < 0 || interrupt > interrupt_data->num_interrupts)
+		return -EINVAL;
+
+	interrupt_data->eventfd_ctxs[interrupt] = ctx;
+	return 0;
+}
+
+int gasket_interrupt_clear_eventfd(
+	struct gasket_interrupt_data *interrupt_data, int interrupt)
+{
+	if (interrupt < 0 || interrupt > interrupt_data->num_interrupts)
+		return -EINVAL;
+
+	interrupt_data->eventfd_ctxs[interrupt] = NULL;
+	return 0;
+}
+
+int gasket_interrupt_trigger_eventfd(
+	struct gasket_interrupt_data *interrupt_data, int interrupt)
+{
+	struct eventfd_ctx *ctx = interrupt_data->eventfd_ctxs[interrupt];
+
+	if (!ctx)
+		return -EINVAL;
+
+	eventfd_signal(ctx, 1);
+	return 0;
+}
+
+struct msix_entry *gasket_interrupt_get_msix_entries(
+	struct gasket_interrupt_data *interrupt_data)
+{
+	return interrupt_data->msix_entries;
+}
+
+struct eventfd_ctx **gasket_interrupt_get_eventfd_ctxs(
+	struct gasket_interrupt_data *interrupt_data)
+{
+	return interrupt_data->eventfd_ctxs;
+}
+EXPORT_SYMBOL(gasket_interrupt_get_eventfd_ctxs);
+
+static ssize_t interrupt_sysfs_show(
+	struct device *device, struct device_attribute *attr, char *buf)
+{
+	int i, ret;
+	ssize_t written = 0, total_written = 0;
+	struct gasket_interrupt_data *interrupt_data;
+	struct gasket_dev *gasket_dev;
+	struct gasket_sysfs_attribute *gasket_attr;
+	enum interrupt_sysfs_attribute_type sysfs_type;
+
+	gasket_dev = gasket_sysfs_get_device_data(device);
+	if (!gasket_dev) {
+		gasket_nodev_error(
+			"No sysfs mapping found for device 0x%p", device);
+		return 0;
+	}
+
+	gasket_attr = gasket_sysfs_get_attr(device, attr);
+	if (!gasket_attr) {
+		gasket_nodev_error(
+			"No sysfs attr data found for device 0x%p", device);
+		gasket_sysfs_put_device_data(device, gasket_dev);
+		return 0;
+	}
+
+	sysfs_type = (enum interrupt_sysfs_attribute_type)
+		gasket_attr->data.attr_type;
+	interrupt_data = gasket_dev->interrupt_data;
+	switch (sysfs_type) {
+	case ATTR_INTERRUPT_COUNTS:
+		for (i = 0; i < interrupt_data->num_interrupts; ++i) {
+			written =
+				scnprintf(buf, PAGE_SIZE - total_written,
+					  "0x%02x: %ld\n", i,
+					  interrupt_data->interrupt_counts[i]);
+			total_written += written;
+			buf += written;
+		}
+		ret = total_written;
+		break;
+	default:
+		gasket_log_error(
+			gasket_dev, "Unknown attribute: %s", attr->attr.name);
+		ret = 0;
+		break;
+	}
+
+	gasket_sysfs_put_attr(device, gasket_attr);
+	gasket_sysfs_put_device_data(device, gasket_dev);
+	return ret;
+}
+
+/*
+ * MSIX interrupt handler, used with PCI driver.
+ */
+static irqreturn_t gasket_msix_interrupt_handler(int irq, void *dev_id)
+{
+	struct eventfd_ctx *ctx;
+	struct gasket_interrupt_data *interrupt_data = dev_id;
+	int interrupt = -1;
+	int i;
+
+	/* If this linear lookup is a problem, we can maintain a map/hash. */
+	for (i = 0; i < interrupt_data->num_interrupts; i++) {
+		if (interrupt_data->msix_entries[i].vector == irq) {
+			interrupt = interrupt_data->msix_entries[i].entry;
+			break;
+		}
+	}
+	if (interrupt == -1) {
+		gasket_nodev_error("Received unknown irq %d", irq);
+		return IRQ_HANDLED;
+	}
+	trace_gasket_interrupt_event(interrupt_data->name, interrupt);
+
+	ctx = interrupt_data->eventfd_ctxs[interrupt];
+	if (ctx)
+		eventfd_signal(ctx, 1);
+
+	++(interrupt_data->interrupt_counts[interrupt]);
+
+	return IRQ_HANDLED;
+}