linux-stable/drivers/uio/uio_pci_generic.c
Jan Kiszka fb51ccbf21 PCI: Rework config space blocking services
pci_block_user_cfg_access was designed for the use case that a single
context, the IPR driver, temporarily delays user space accesses to the
config space via sysfs. This assumption became invalid by the time
pci_dev_reset was added as locking instance. Today, if you run two loops
in parallel that reset the same device via sysfs, you end up with a
kernel BUG as pci_block_user_cfg_access detect the broken assumption.

This reworks the pci_block_user_cfg_access to a sleeping service
pci_cfg_access_lock and an atomic-compatible variant called
pci_cfg_access_trylock. The former not only blocks user space access as
before but also waits if access was already locked. The latter service
just returns false in this case, allowing the caller to resolve the
conflict instead of raising a BUG.

Adaptions of the ipr driver were originally written by Brian King.

Acked-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
2012-01-06 12:10:33 -08:00

205 lines
5.6 KiB
C

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