drivers/pci/access.c

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