drivers/hwspinlock/omap_hwspinlock.c

Source file repositories/reference/linux-study-clean/drivers/hwspinlock/omap_hwspinlock.c

File Facts

System
Linux kernel
Corpus path
drivers/hwspinlock/omap_hwspinlock.c
Extension
.c
Size
4304 bytes
Lines
160
Domain
Driver Families
Bucket
drivers/hwspinlock
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 * OMAP hardware spinlock driver
 *
 * Copyright (C) 2010-2021 Texas Instruments Incorporated - https://www.ti.com
 *
 * Contact: Simon Que <sque@ti.com>
 *          Hari Kanigeri <h-kanigeri2@ti.com>
 *          Ohad Ben-Cohen <ohad@wizery.com>
 *          Suman Anna <s-anna@ti.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/hwspinlock.h>
#include <linux/of.h>
#include <linux/platform_device.h>

#include "hwspinlock_internal.h"

/* Spinlock register offsets */
#define SYSSTATUS_OFFSET		0x0014
#define LOCK_BASE_OFFSET		0x0800

#define SPINLOCK_NUMLOCKS_BIT_OFFSET	(24)

/* Possible values of SPINLOCK_LOCK_REG */
#define SPINLOCK_NOTTAKEN		(0)	/* free */
#define SPINLOCK_TAKEN			(1)	/* locked */

static int omap_hwspinlock_trylock(struct hwspinlock *lock)
{
	void __iomem *lock_addr = lock->priv;

	/* attempt to acquire the lock by reading its value */
	return (SPINLOCK_NOTTAKEN == readl(lock_addr));
}

static void omap_hwspinlock_unlock(struct hwspinlock *lock)
{
	void __iomem *lock_addr = lock->priv;

	/* release the lock by writing 0 to it */
	writel(SPINLOCK_NOTTAKEN, lock_addr);
}

/*
 * relax the OMAP interconnect while spinning on it.
 *
 * The specs recommended that the retry delay time will be
 * just over half of the time that a requester would be
 * expected to hold the lock.
 *
 * The number below is taken from an hardware specs example,
 * obviously it is somewhat arbitrary.
 */
static void omap_hwspinlock_relax(struct hwspinlock *lock)
{
	ndelay(50);
}

static const struct hwspinlock_ops omap_hwspinlock_ops = {
	.trylock = omap_hwspinlock_trylock,
	.unlock = omap_hwspinlock_unlock,
	.relax = omap_hwspinlock_relax,
};

static int omap_hwspinlock_probe(struct platform_device *pdev)
{
	struct hwspinlock_device *bank;
	void __iomem *io_base;
	int num_locks, i, ret;
	/* Only a single hwspinlock block device is supported */
	int base_id = 0;

	io_base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(io_base))
		return PTR_ERR(io_base);

	/*
	 * make sure the module is enabled and clocked before reading
	 * the module SYSSTATUS register
	 */

Annotation

Implementation Notes