blob: 313da35984afece38a4614e427431d5ab4be6772 [file] [log] [blame]
Michael S. Tsirkinccb86a62009-07-20 10:29:34 +03001/* uio_pci_generic - generic UIO driver for PCI 2.3 devices
2 *
3 * Copyright (C) 2009 Red Hat, Inc.
4 * Author: Michael S. Tsirkin <mst@redhat.com>
5 *
6 * This work is licensed under the terms of the GNU GPL, version 2.
7 *
8 * Since the driver does not declare any device ids, you must allocate
9 * id and bind the device to the driver yourself. For example:
10 *
11 * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
12 * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
13 * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
14 * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
15 * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
16 *
17 * Driver won't bind to devices which do not support the Interrupt Disable Bit
18 * in the command register. All devices compliant to PCI 2.3 (circa 2002) and
19 * all compliant PCI Express devices should support this bit.
20 */
21
22#include <linux/device.h>
23#include <linux/module.h>
24#include <linux/pci.h>
25#include <linux/uio_driver.h>
26#include <linux/spinlock.h>
27
28#define DRIVER_VERSION "0.01.0"
29#define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>"
30#define DRIVER_DESC "Generic UIO driver for PCI 2.3 devices"
31
32struct uio_pci_generic_dev {
33 struct uio_info info;
34 struct pci_dev *pdev;
35 spinlock_t lock; /* guards command register accesses */
36};
37
38static inline struct uio_pci_generic_dev *
39to_uio_pci_generic_dev(struct uio_info *info)
40{
41 return container_of(info, struct uio_pci_generic_dev, info);
42}
43
44/* Interrupt handler. Read/modify/write the command register to disable
45 * the interrupt. */
46static irqreturn_t irqhandler(int irq, struct uio_info *info)
47{
48 struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
49 struct pci_dev *pdev = gdev->pdev;
50 irqreturn_t ret = IRQ_NONE;
51 u32 cmd_status_dword;
52 u16 origcmd, newcmd, status;
53
54 /* We do a single dword read to retrieve both command and status.
55 * Document assumptions that make this possible. */
56 BUILD_BUG_ON(PCI_COMMAND % 4);
57 BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
58
59 spin_lock_irq(&gdev->lock);
60 pci_block_user_cfg_access(pdev);
61
62 /* Read both command and status registers in a single 32-bit operation.
63 * Note: we could cache the value for command and move the status read
64 * out of the lock if there was a way to get notified of user changes
65 * to command register through sysfs. Should be good for shared irqs. */
66 pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword);
67 origcmd = cmd_status_dword;
68 status = cmd_status_dword >> 16;
69
70 /* Check interrupt status register to see whether our device
71 * triggered the interrupt. */
72 if (!(status & PCI_STATUS_INTERRUPT))
73 goto done;
74
75 /* We triggered the interrupt, disable it. */
76 newcmd = origcmd | PCI_COMMAND_INTX_DISABLE;
77 if (newcmd != origcmd)
78 pci_write_config_word(pdev, PCI_COMMAND, newcmd);
79
80 /* UIO core will signal the user process. */
81 ret = IRQ_HANDLED;
82done:
83
84 pci_unblock_user_cfg_access(pdev);
85 spin_unlock_irq(&gdev->lock);
86 return ret;
87}
88
89/* Verify that the device supports Interrupt Disable bit in command register,
90 * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly
91 * in PCI 2.2. */
92static int __devinit verify_pci_2_3(struct pci_dev *pdev)
93{
94 u16 orig, new;
95 int err = 0;
96
97 pci_block_user_cfg_access(pdev);
98 pci_read_config_word(pdev, PCI_COMMAND, &orig);
99 pci_write_config_word(pdev, PCI_COMMAND,
100 orig ^ PCI_COMMAND_INTX_DISABLE);
101 pci_read_config_word(pdev, PCI_COMMAND, &new);
102 /* There's no way to protect against
103 * hardware bugs or detect them reliably, but as long as we know
104 * what the value should be, let's go ahead and check it. */
105 if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
106 err = -EBUSY;
107 dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: "
108 "driver or HW bug?\n", orig, new);
109 goto err;
110 }
111 if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) {
112 dev_warn(&pdev->dev, "Device does not support "
113 "disabling interrupts: unable to bind.\n");
114 err = -ENODEV;
115 goto err;
116 }
117 /* Now restore the original value. */
118 pci_write_config_word(pdev, PCI_COMMAND, orig);
119err:
120 pci_unblock_user_cfg_access(pdev);
121 return err;
122}
123
124static int __devinit probe(struct pci_dev *pdev,
125 const struct pci_device_id *id)
126{
127 struct uio_pci_generic_dev *gdev;
128 int err;
129
130 if (!pdev->irq) {
131 dev_warn(&pdev->dev, "No IRQ assigned to device: "
132 "no support for interrupts?\n");
133 return -ENODEV;
134 }
135
136 err = pci_enable_device(pdev);
137 if (err) {
138 dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
139 __func__, err);
140 return err;
141 }
142
143 err = verify_pci_2_3(pdev);
144 if (err)
145 goto err_verify;
146
147 gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
148 if (!gdev) {
149 err = -ENOMEM;
150 goto err_alloc;
151 }
152
153 gdev->info.name = "uio_pci_generic";
154 gdev->info.version = DRIVER_VERSION;
155 gdev->info.irq = pdev->irq;
156 gdev->info.irq_flags = IRQF_SHARED;
157 gdev->info.handler = irqhandler;
158 gdev->pdev = pdev;
159 spin_lock_init(&gdev->lock);
160
161 if (uio_register_device(&pdev->dev, &gdev->info))
162 goto err_register;
163 pci_set_drvdata(pdev, gdev);
164
165 return 0;
166err_register:
167 kfree(gdev);
168err_alloc:
169err_verify:
170 pci_disable_device(pdev);
171 return err;
172}
173
174static void remove(struct pci_dev *pdev)
175{
176 struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
177
178 uio_unregister_device(&gdev->info);
179 pci_disable_device(pdev);
180 kfree(gdev);
181}
182
183static struct pci_driver driver = {
184 .name = "uio_pci_generic",
185 .id_table = NULL, /* only dynamic id's */
186 .probe = probe,
187 .remove = remove,
188};
189
190static int __init init(void)
191{
192 pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
193 return pci_register_driver(&driver);
194}
195
196static void __exit cleanup(void)
197{
198 pci_unregister_driver(&driver);
199}
200
201module_init(init);
202module_exit(cleanup);
203
204MODULE_VERSION(DRIVER_VERSION);
205MODULE_LICENSE("GPL v2");
206MODULE_AUTHOR(DRIVER_AUTHOR);
207MODULE_DESCRIPTION(DRIVER_DESC);