UIO: add automata sercos3 pci card support

Here is a new version of the patch to support the Automata Sercos III
PCI card driver. I now check that the IRQ is enabled before accepting
the interrupt.

I still use a logical OR to store the enabled interrupts and I've
added a second use of a logical OR when restoring the enabled
interrupts. I added an explanation of why I do this in comments at the
top of the source file.

Since I use a logical OR, I also removed the extra checks if the
Interrupt Enable Register and ier0_cache are 0.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/uio/Kconfig

@@ -58,4 +58,17 @@ config UIO_SMX
 
 	  If you compile this as a module, it will be called uio_smx.
 
+config UIO_SERCOS3
+	tristate "Automata Sercos III PCI card driver"
+	default n
+	help
+	  Userspace I/O interface for the Sercos III PCI card from
+	  Automata GmbH. The userspace part of this driver will be
+	  available for download from the Automata GmbH web site.
+
+	  Automata GmbH:        http://www.automataweb.com
+	  Sercos III interface: http://www.sercos.com
+
+	  If you compile this as a module, it will be called uio_sercos3.
+
 endif

drivers/uio/Makefile

@@ -3,3 +3,4 @@ obj-$(CONFIG_UIO_CIF)	+= uio_cif.o
 obj-$(CONFIG_UIO_PDRV)	+= uio_pdrv.o
 obj-$(CONFIG_UIO_PDRV_GENIRQ)	+= uio_pdrv_genirq.o
 obj-$(CONFIG_UIO_SMX)	+= uio_smx.o
+obj-$(CONFIG_UIO_SERCOS3)	+= uio_sercos3.o

drivers/uio/uio_sercos3.c

@@ -0,0 +1,243 @@
+/* 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>
+
+/* 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 __devinit 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_DISABLED | 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);
+	pci_set_drvdata(dev, NULL);
+	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[] __devinitdata = {
+	{
+		.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,
+};
+
+static int __init sercos3_init_module(void)
+{
+	return pci_register_driver(&sercos3_pci_driver);
+}
+
+static void __exit sercos3_exit_module(void)
+{
+	pci_unregister_driver(&sercos3_pci_driver);
+}
+
+module_init(sercos3_init_module);
+module_exit(sercos3_exit_module);
+
+MODULE_DESCRIPTION("UIO driver for the Automata Sercos III PCI card");
+MODULE_AUTHOR("John Ogness <john.ogness@linutronix.de>");
+MODULE_LICENSE("GPL v2");