drivers/pci/access.c

   1 #include <linux/pci.h>
   2 #include <linux/module.h>
   3 #include <linux/sched.h>
   4 #include <linux/ioport.h>
   5 #include <linux/wait.h>
   6
   7 #include "pci.h"
   8
   9 /*
  10  * This interrupt-safe spinlock protects all accesses to PCI
  11  * configuration space.
  12  */
  13
  14 static DEFINE_SPINLOCK(pci_lock);
  15
  16 /*
  17  *  Wrappers for all PCI configuration access functions.  They just check
  18  *  alignment, do locking and call the low-level functions pointed to
  19  *  by pci_dev->ops.
  20  */
  21
  22 #define PCI_byte_BAD 0
  23 #define PCI_word_BAD (pos & 1)
  24 #define PCI_dword_BAD (pos & 3)
  25
  26 #define PCI_OP_READ(size,type,len) \
  27 int pci_bus_read_config_##size \
  28         (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \
  29 {                                                                       \
  30         int res;                                                        \
  31         unsigned long flags;                                            \
  32         u32 data = 0;                                                   \
  33         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
  34         spin_lock_irqsave(&pci_lock, flags);                            \
  35         res = bus->ops->read(bus, devfn, pos, len, &data);              \
  36         *value = (type)data;                                            \
  37         spin_unlock_irqrestore(&pci_lock, flags);                       \
  38         return res;                                                     \
  39 }
  40
  41 #define PCI_OP_WRITE(size,type,len) \
  42 int pci_bus_write_config_##size \
  43         (struct pci_bus *bus, unsigned int devfn, int pos, type value)  \
  44 {                                                                       \
  45         int res;                                                        \
  46         unsigned long flags;                                            \
  47         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
  48         spin_lock_irqsave(&pci_lock, flags);                            \
  49         res = bus->ops->write(bus, devfn, pos, len, value);             \
  50         spin_unlock_irqrestore(&pci_lock, flags);                       \
  51         return res;                                                     \
  52 }
  53
  54 PCI_OP_READ(byte, u8, 1)
  55 PCI_OP_READ(word, u16, 2)
  56 PCI_OP_READ(dword, u32, 4)
  57 PCI_OP_WRITE(byte, u8, 1)
  58 PCI_OP_WRITE(word, u16, 2)
  59 PCI_OP_WRITE(dword, u32, 4)
  60
  61 EXPORT_SYMBOL(pci_bus_read_config_byte);
  62 EXPORT_SYMBOL(pci_bus_read_config_word);
  63 EXPORT_SYMBOL(pci_bus_read_config_dword);
  64 EXPORT_SYMBOL(pci_bus_write_config_byte);
  65 EXPORT_SYMBOL(pci_bus_write_config_word);
  66 EXPORT_SYMBOL(pci_bus_write_config_dword);
  67
  68 /*
  69  * The following routines are to prevent the user from accessing PCI config
  70  * space when it's unsafe to do so.  Some devices require this during BIST and
  71  * we're required to prevent it during D-state transitions.
  72  *
  73  * We have a bit per device to indicate it's blocked and a global wait queue
  74  * for callers to sleep on until devices are unblocked.
  75  */
  76 static DECLARE_WAIT_QUEUE_HEAD(pci_ucfg_wait);
  77
  78 static noinline void pci_wait_ucfg(struct pci_dev *dev)
  79 {
  80         DECLARE_WAITQUEUE(wait, current);
  81
  82         __add_wait_queue(&pci_ucfg_wait, &wait);
  83         do {
  84                 set_current_state(TASK_UNINTERRUPTIBLE);
  85                 spin_unlock_irq(&pci_lock);
  86                 schedule();
  87                 spin_lock_irq(&pci_lock);
  88         } while (dev->block_ucfg_access);
  89         __remove_wait_queue(&pci_ucfg_wait, &wait);
  90 }
  91
  92 #define PCI_USER_READ_CONFIG(size,type)                                 \
  93 int pci_user_read_config_##size                                         \
  94         (struct pci_dev *dev, int pos, type *val)                       \
  95 {                                                                       \
  96         int ret = 0;                                                    \
  97         u32 data = -1;                                                  \
  98         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
  99         spin_lock_irq(&pci_lock);                                       \
 100         if (unlikely(dev->block_ucfg_access)) pci_wait_ucfg(dev);       \
 101         ret = dev->bus->ops->read(dev->bus, dev->devfn,                 \
 102                                         pos, sizeof(type), &data);      \
 103         spin_unlock_irq(&pci_lock);                                     \
 104         *val = (type)data;                                              \
 105         return ret;                                                     \
 106 }
 107
 108 #define PCI_USER_WRITE_CONFIG(size,type)                                \
 109 int pci_user_write_config_##size                                        \
 110         (struct pci_dev *dev, int pos, type val)                        \
 111 {                                                                       \
 112         int ret = -EIO;                                                 \
 113         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
 114         spin_lock_irq(&pci_lock);                                       \
 115         if (unlikely(dev->block_ucfg_access)) pci_wait_ucfg(dev);       \
 116         ret = dev->bus->ops->write(dev->bus, dev->devfn,                \
 117                                         pos, sizeof(type), val);        \
 118         spin_unlock_irq(&pci_lock);                                     \
 119         return ret;                                                     \
 120 }
 121
 122 PCI_USER_READ_CONFIG(byte, u8)
 123 PCI_USER_READ_CONFIG(word, u16)
 124 PCI_USER_READ_CONFIG(dword, u32)
 125 PCI_USER_WRITE_CONFIG(byte, u8)
 126 PCI_USER_WRITE_CONFIG(word, u16)
 127 PCI_USER_WRITE_CONFIG(dword, u32)
 128
 129 /**
 130  * pci_block_user_cfg_access - Block userspace PCI config reads/writes
 131  * @dev:        pci device struct
 132  *
 133  * When user access is blocked, any reads or writes to config space will
 134  * sleep until access is unblocked again.  We don't allow nesting of
 135  * block/unblock calls.
 136  */
 137 void pci_block_user_cfg_access(struct pci_dev *dev)
 138 {
 139         unsigned long flags;
 140         int was_blocked;
 141
 142         spin_lock_irqsave(&pci_lock, flags);
 143         was_blocked = dev->block_ucfg_access;
 144         dev->block_ucfg_access = 1;
 145         spin_unlock_irqrestore(&pci_lock, flags);
 146
 147         /* If we BUG() inside the pci_lock, we're guaranteed to hose
 148          * the machine */
 149         BUG_ON(was_blocked);
 150 }
 151 EXPORT_SYMBOL_GPL(pci_block_user_cfg_access);
 152
 153 /**
 154  * pci_unblock_user_cfg_access - Unblock userspace PCI config reads/writes
 155  * @dev:        pci device struct
 156  *
 157  * This function allows userspace PCI config accesses to resume.
 158  */
 159 void pci_unblock_user_cfg_access(struct pci_dev *dev)
 160 {
 161         unsigned long flags;
 162
 163         spin_lock_irqsave(&pci_lock, flags);
 164
 165         /* This indicates a problem in the caller, but we don't need
 166          * to kill them, unlike a double-block above. */
 167         WARN_ON(!dev->block_ucfg_access);
 168
 169         dev->block_ucfg_access = 0;
 170         wake_up_all(&pci_ucfg_wait);
 171         spin_unlock_irqrestore(&pci_lock, flags);
 172 }
 173 EXPORT_SYMBOL_GPL(pci_unblock_user_cfg_access);