File: uio_sercos3.c

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// SPDX-License-Identifier: GPL-2.0
/* sercos3: UIO driver for the Automata Sercos III PCI card

   Copyright (C) 2008 Linutronix GmbH
     Author: John Ogness <john.ogness@linutronix.de>

   This is a straight-forward UIO driver, where interrupts are disabled
   by the interrupt handler and re-enabled via a write to the UIO device
   by the userspace-part.

   The only part that may seem odd is the use of a logical OR when
   storing and restoring enabled interrupts. This is done because the
   userspace-part could directly modify the Interrupt Enable Register
   at any time. To reduce possible conflicts, the kernel driver uses
   a logical OR to make more controlled changes (rather than blindly
   overwriting previous values).

   Race conditions exist if the userspace-part directly modifies the
   Interrupt Enable Register while in operation. The consequences are
   that certain interrupts would fail to be enabled or disabled. For
   this reason, the userspace-part should only directly modify the
   Interrupt Enable Register at the beginning (to get things going).
   The userspace-part can safely disable interrupts at any time using
   a write to the UIO device.
*/

#include <linux/device.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/uio_driver.h>
#include <linux/io.h>
#include <linux/slab.h>

/* ID's for SERCOS III PCI card (PLX 9030) */
#define SERCOS_SUB_VENDOR_ID  0x1971
#define SERCOS_SUB_SYSID_3530 0x3530
#define SERCOS_SUB_SYSID_3535 0x3535
#define SERCOS_SUB_SYSID_3780 0x3780

/* Interrupt Enable Register */
#define IER0_OFFSET 0x08

/* Interrupt Status Register */
#define ISR0_OFFSET 0x18

struct sercos3_priv {
	u32 ier0_cache;
	spinlock_t ier0_cache_lock;
};

/* this function assumes ier0_cache_lock is locked! */
static void sercos3_disable_interrupts(struct uio_info *info,
				       struct sercos3_priv *priv)
{
	void __iomem *ier0 = info->mem[3].internal_addr + IER0_OFFSET;

	/* add enabled interrupts to cache */
	priv->ier0_cache |= ioread32(ier0);

	/* disable interrupts */
	iowrite32(0, ier0);
}

/* this function assumes ier0_cache_lock is locked! */
static void sercos3_enable_interrupts(struct uio_info *info,
				      struct sercos3_priv *priv)
{
	void __iomem *ier0 = info->mem[3].internal_addr + IER0_OFFSET;

	/* restore previously enabled interrupts */
	iowrite32(ioread32(ier0) | priv->ier0_cache, ier0);
	priv->ier0_cache = 0;
}

static irqreturn_t sercos3_handler(int irq, struct uio_info *info)
{
	struct sercos3_priv *priv = info->priv;
	void __iomem *isr0 = info->mem[3].internal_addr + ISR0_OFFSET;
	void __iomem *ier0 = info->mem[3].internal_addr + IER0_OFFSET;

	if (!(ioread32(isr0) & ioread32(ier0)))
		return IRQ_NONE;

	spin_lock(&priv->ier0_cache_lock);
	sercos3_disable_interrupts(info, priv);
	spin_unlock(&priv->ier0_cache_lock);

	return IRQ_HANDLED;
}

static int sercos3_irqcontrol(struct uio_info *info, s32 irq_on)
{
	struct sercos3_priv *priv = info->priv;

	spin_lock_irq(&priv->ier0_cache_lock);
	if (irq_on)
		sercos3_enable_interrupts(info, priv);
	else
		sercos3_disable_interrupts(info, priv);
	spin_unlock_irq(&priv->ier0_cache_lock);

	return 0;
}

static int sercos3_setup_iomem(struct pci_dev *dev, struct uio_info *info,
			       int n, int pci_bar)
{
	info->mem[n].addr = pci_resource_start(dev, pci_bar);
	if (!info->mem[n].addr)
		return -1;
	info->mem[n].internal_addr = ioremap(pci_resource_start(dev, pci_bar),
					     pci_resource_len(dev, pci_bar));
	if (!info->mem[n].internal_addr)
		return -1;
	info->mem[n].size = pci_resource_len(dev, pci_bar);
	info->mem[n].memtype = UIO_MEM_PHYS;
	return 0;
}

static int sercos3_pci_probe(struct pci_dev *dev,
				       const struct pci_device_id *id)
{
	struct uio_info *info;
	struct sercos3_priv *priv;
	int i;

	info = kzalloc(sizeof(struct uio_info), GFP_KERNEL);
	if (!info)
		return -ENOMEM;

	priv = kzalloc(sizeof(struct sercos3_priv), GFP_KERNEL);
	if (!priv)
		goto out_free;

	if (pci_enable_device(dev))
		goto out_free_priv;

	if (pci_request_regions(dev, "sercos3"))
		goto out_disable;

	/* we only need PCI BAR's 0, 2, 3, 4, 5 */
	if (sercos3_setup_iomem(dev, info, 0, 0))
		goto out_unmap;
	if (sercos3_setup_iomem(dev, info, 1, 2))
		goto out_unmap;
	if (sercos3_setup_iomem(dev, info, 2, 3))
		goto out_unmap;
	if (sercos3_setup_iomem(dev, info, 3, 4))
		goto out_unmap;
	if (sercos3_setup_iomem(dev, info, 4, 5))
		goto out_unmap;

	spin_lock_init(&priv->ier0_cache_lock);
	info->priv = priv;
	info->name = "Sercos_III_PCI";
	info->version = "0.0.1";
	info->irq = dev->irq;
	info->irq_flags = IRQF_SHARED;
	info->handler = sercos3_handler;
	info->irqcontrol = sercos3_irqcontrol;

	pci_set_drvdata(dev, info);

	if (uio_register_device(&dev->dev, info))
		goto out_unmap;

	return 0;

out_unmap:
	for (i = 0; i < 5; i++) {
		if (info->mem[i].internal_addr)
			iounmap(info->mem[i].internal_addr);
	}
	pci_release_regions(dev);
out_disable:
	pci_disable_device(dev);
out_free_priv:
	kfree(priv);
out_free:
	kfree(info);
	return -ENODEV;
}

static void sercos3_pci_remove(struct pci_dev *dev)
{
	struct uio_info *info = pci_get_drvdata(dev);
	int i;

	uio_unregister_device(info);
	pci_release_regions(dev);
	pci_disable_device(dev);
	for (i = 0; i < 5; i++) {
		if (info->mem[i].internal_addr)
			iounmap(info->mem[i].internal_addr);
	}
	kfree(info->priv);
	kfree(info);
}

static struct pci_device_id sercos3_pci_ids[] = {
	{
		.vendor =       PCI_VENDOR_ID_PLX,
		.device =       PCI_DEVICE_ID_PLX_9030,
		.subvendor =    SERCOS_SUB_VENDOR_ID,
		.subdevice =    SERCOS_SUB_SYSID_3530,
	},
	{
		.vendor =       PCI_VENDOR_ID_PLX,
		.device =       PCI_DEVICE_ID_PLX_9030,
		.subvendor =    SERCOS_SUB_VENDOR_ID,
		.subdevice =    SERCOS_SUB_SYSID_3535,
	},
	{
		.vendor =       PCI_VENDOR_ID_PLX,
		.device =       PCI_DEVICE_ID_PLX_9030,
		.subvendor =    SERCOS_SUB_VENDOR_ID,
		.subdevice =    SERCOS_SUB_SYSID_3780,
	},
	{ 0, }
};

static struct pci_driver sercos3_pci_driver = {
	.name = "sercos3",
	.id_table = sercos3_pci_ids,
	.probe = sercos3_pci_probe,
	.remove = sercos3_pci_remove,
};

module_pci_driver(sercos3_pci_driver);
MODULE_DESCRIPTION("UIO driver for the Automata Sercos III PCI card");
MODULE_AUTHOR("John Ogness <john.ogness@linutronix.de>");
MODULE_LICENSE("GPL v2");