![Hans J. Koch](/assets/img/avatar_default.png)
The spin_lock in uio_pci_generic.c is only used in the interrupt handler, which cannot be executed twice at the same time. That makes the lock rather pointless. This patch removes it. Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Chris Wright <chrisw@redhat.com> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Anthony Foiani <anthony.foiani@gmail.com> Reported-by: Anthony Foiani <anthony.foiani@gmail.com> Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Hans J. Koch <hjk@hansjkoch.de> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
205 lines
5.6 KiB
C
205 lines
5.6 KiB
C
/* uio_pci_generic - generic UIO driver for PCI 2.3 devices
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*
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* Copyright (C) 2009 Red Hat, Inc.
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* Author: Michael S. Tsirkin <mst@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2.
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*
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* Since the driver does not declare any device ids, you must allocate
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* id and bind the device to the driver yourself. For example:
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*
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* # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
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* # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
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* # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
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* # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
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* .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
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*
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* Driver won't bind to devices which do not support the Interrupt Disable Bit
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* in the command register. All devices compliant to PCI 2.3 (circa 2002) and
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* all compliant PCI Express devices should support this bit.
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*/
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#include <linux/device.h>
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#include <linux/module.h>
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#include <linux/pci.h>
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#include <linux/slab.h>
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#include <linux/uio_driver.h>
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#define DRIVER_VERSION "0.01.0"
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#define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>"
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#define DRIVER_DESC "Generic UIO driver for PCI 2.3 devices"
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struct uio_pci_generic_dev {
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struct uio_info info;
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struct pci_dev *pdev;
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};
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static inline struct uio_pci_generic_dev *
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to_uio_pci_generic_dev(struct uio_info *info)
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{
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return container_of(info, struct uio_pci_generic_dev, info);
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}
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/* Interrupt handler. Read/modify/write the command register to disable
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* the interrupt. */
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static irqreturn_t irqhandler(int irq, struct uio_info *info)
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{
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struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
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struct pci_dev *pdev = gdev->pdev;
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irqreturn_t ret = IRQ_NONE;
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u32 cmd_status_dword;
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u16 origcmd, newcmd, status;
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/* We do a single dword read to retrieve both command and status.
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* Document assumptions that make this possible. */
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BUILD_BUG_ON(PCI_COMMAND % 4);
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BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
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pci_block_user_cfg_access(pdev);
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/* Read both command and status registers in a single 32-bit operation.
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* Note: we could cache the value for command and move the status read
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* out of the lock if there was a way to get notified of user changes
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* to command register through sysfs. Should be good for shared irqs. */
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pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword);
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origcmd = cmd_status_dword;
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status = cmd_status_dword >> 16;
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/* Check interrupt status register to see whether our device
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* triggered the interrupt. */
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if (!(status & PCI_STATUS_INTERRUPT))
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goto done;
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/* We triggered the interrupt, disable it. */
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newcmd = origcmd | PCI_COMMAND_INTX_DISABLE;
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if (newcmd != origcmd)
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pci_write_config_word(pdev, PCI_COMMAND, newcmd);
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/* UIO core will signal the user process. */
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ret = IRQ_HANDLED;
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done:
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pci_unblock_user_cfg_access(pdev);
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return ret;
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}
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/* Verify that the device supports Interrupt Disable bit in command register,
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* per PCI 2.3, by flipping this bit and reading it back: this bit was readonly
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* in PCI 2.2. */
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static int __devinit verify_pci_2_3(struct pci_dev *pdev)
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{
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u16 orig, new;
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int err = 0;
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pci_block_user_cfg_access(pdev);
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pci_read_config_word(pdev, PCI_COMMAND, &orig);
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pci_write_config_word(pdev, PCI_COMMAND,
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orig ^ PCI_COMMAND_INTX_DISABLE);
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pci_read_config_word(pdev, PCI_COMMAND, &new);
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/* There's no way to protect against
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* hardware bugs or detect them reliably, but as long as we know
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* what the value should be, let's go ahead and check it. */
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if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
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err = -EBUSY;
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dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: "
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"driver or HW bug?\n", orig, new);
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goto err;
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}
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if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) {
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dev_warn(&pdev->dev, "Device does not support "
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"disabling interrupts: unable to bind.\n");
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err = -ENODEV;
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goto err;
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}
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/* Now restore the original value. */
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pci_write_config_word(pdev, PCI_COMMAND, orig);
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err:
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pci_unblock_user_cfg_access(pdev);
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return err;
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}
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static int __devinit probe(struct pci_dev *pdev,
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const struct pci_device_id *id)
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{
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struct uio_pci_generic_dev *gdev;
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int err;
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err = pci_enable_device(pdev);
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if (err) {
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dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
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__func__, err);
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return err;
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}
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if (!pdev->irq) {
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dev_warn(&pdev->dev, "No IRQ assigned to device: "
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"no support for interrupts?\n");
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pci_disable_device(pdev);
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return -ENODEV;
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}
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err = verify_pci_2_3(pdev);
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if (err)
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goto err_verify;
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gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
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if (!gdev) {
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err = -ENOMEM;
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goto err_alloc;
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}
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gdev->info.name = "uio_pci_generic";
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gdev->info.version = DRIVER_VERSION;
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gdev->info.irq = pdev->irq;
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gdev->info.irq_flags = IRQF_SHARED;
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gdev->info.handler = irqhandler;
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gdev->pdev = pdev;
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if (uio_register_device(&pdev->dev, &gdev->info))
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goto err_register;
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pci_set_drvdata(pdev, gdev);
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return 0;
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err_register:
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kfree(gdev);
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err_alloc:
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err_verify:
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pci_disable_device(pdev);
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return err;
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}
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static void remove(struct pci_dev *pdev)
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{
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struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
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uio_unregister_device(&gdev->info);
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pci_disable_device(pdev);
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kfree(gdev);
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}
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static struct pci_driver driver = {
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.name = "uio_pci_generic",
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.id_table = NULL, /* only dynamic id's */
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.probe = probe,
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.remove = remove,
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};
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static int __init init(void)
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{
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pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
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return pci_register_driver(&driver);
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}
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static void __exit cleanup(void)
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{
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pci_unregister_driver(&driver);
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}
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module_init(init);
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module_exit(cleanup);
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MODULE_VERSION(DRIVER_VERSION);
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR(DRIVER_AUTHOR);
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MODULE_DESCRIPTION(DRIVER_DESC);
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