5 files changed, 59 insertions, 22 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 84ec9c8f6703..e5ae3a0c13bb 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -329,8 +329,8 @@ static int pci_default_resume(struct pci_dev *pci_dev)
         /* restore the PCI config space */
         pci_restore_state(pci_dev);
         /* if the device was enabled before suspend, reenable */
-        if (pci_dev->is_enabled)
-                retval = pci_enable_device(pci_dev);
+        if (atomic_read(&pci_dev->enable_cnt))
+                retval = __pci_enable_device(pci_dev);
         /* if the device was busmaster before the suspend, make it busmaster again */
         if (pci_dev->is_busmaster)
                 pci_set_master(pci_dev);
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index f952bfea48a6..7a94076752d0 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -42,7 +42,6 @@ pci_config_attr(subsystem_vendor, "0x%04x\n");
 pci_config_attr(subsystem_device, "0x%04x\n");
 pci_config_attr(class, "0x%06x\n");
 pci_config_attr(irq, "%u\n");
-pci_config_attr(is_enabled, "%u\n");
 
 static ssize_t broken_parity_status_show(struct device *dev,
                                          struct device_attribute *attr,
@@ -112,26 +111,36 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                        (u8)(pci_dev->class >> 16), (u8)(pci_dev->class >> 8),
                        (u8)(pci_dev->class));
 }
-static ssize_t
-is_enabled_store(struct device *dev, struct device_attribute *attr,
-                const char *buf, size_t count)
+
+static ssize_t is_enabled_store(struct device *dev,
+                                struct device_attribute *attr, const char *buf,
+                                size_t count)
 {
+        ssize_t result = -EINVAL;
         struct pci_dev *pdev = to_pci_dev(dev);
-        int retval = 0;
 
         /* this can crash the machine when done on the "wrong" device */
         if (!capable(CAP_SYS_ADMIN))
                 return count;
 
-        if (*buf == '0')
-                pci_disable_device(pdev);
+        if (*buf == '0') {
+                if (atomic_read(&pdev->enable_cnt) != 0)
+                        pci_disable_device(pdev);
+                else
+                        result = -EIO;
+        } else if (*buf == '1')
+                result = pci_enable_device(pdev);
+
+        return result < 0 ? result : count;
+}
 
-        if (*buf == '1')
-                retval = pci_enable_device(pdev);
+static ssize_t is_enabled_show(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+        struct pci_dev *pdev;
 
-        if (retval)
-                return retval;
-        return count;
+        pdev = to_pci_dev (dev);
+        return sprintf (buf, "%u\n", atomic_read(&pdev->enable_cnt));
 }
 
 static ssize_t
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 427991741cf3..5a14b73cf3a1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -612,30 +612,51 @@ pci_enable_device_bars(struct pci_dev *dev, int bars)
 }
 
 /**
- * pci_enable_device - Initialize device before it's used by a driver.
+ * __pci_enable_device - Initialize device before it's used by a driver.
  * @dev: PCI device to be initialized
  *
  *  Initialize device before it's used by a driver. Ask low-level code
  *  to enable I/O and memory. Wake up the device if it was suspended.
  *  Beware, this function can fail.
+ *
+ * Note this function is a backend and is not supposed to be called by
+ * normal code, use pci_enable_device() instead.
  */
 int
-pci_enable_device(struct pci_dev *dev)
+__pci_enable_device(struct pci_dev *dev)
 {
         int err;
 
-        if (dev->is_enabled)
-                return 0;
-
         err = pci_enable_device_bars(dev, (1 << PCI_NUM_RESOURCES) - 1);
         if (err)
                 return err;
         pci_fixup_device(pci_fixup_enable, dev);
-        dev->is_enabled = 1;
         return 0;
 }
 
 /**
+ * pci_enable_device - Initialize device before it's used by a driver.
+ * @dev: PCI device to be initialized
+ *
+ *  Initialize device before it's used by a driver. Ask low-level code
+ *  to enable I/O and memory. Wake up the device if it was suspended.
+ *  Beware, this function can fail.
+ *
+ *  Note we don't actually enable the device many times if we call
+ *  this function repeatedly (we just increment the count).
+ */
+int pci_enable_device(struct pci_dev *dev)
+{
+        int result;
+        if (atomic_add_return(1, &dev->enable_cnt) > 1)
+                return 0;               /* already enabled */
+        result = __pci_enable_device(dev);
+        if (result < 0)
+                atomic_dec(&dev->enable_cnt);
+        return result;
+}
+
+/**
  * pcibios_disable_device - disable arch specific PCI resources for device dev
  * @dev: the PCI device to disable
  *
@@ -651,12 +672,18 @@ void __attribute__ ((weak)) pcibios_disable_device (struct pci_dev *dev) {}
  *
  * Signal to the system that the PCI device is not in use by the system
  * anymore.  This only involves disabling PCI bus-mastering, if active.
+ *
+ * Note we don't actually disable the device until all callers of
+ * pci_device_enable() have called pci_device_disable().
  */
 void
 pci_disable_device(struct pci_dev *dev)
 {
         u16 pci_command;
 
+        if (atomic_sub_return(1, &dev->enable_cnt) != 0)
+                return;
+
         if (dev->msi_enabled)
                 disable_msi_mode(dev, pci_find_capability(dev, PCI_CAP_ID_MSI),
                         PCI_CAP_ID_MSI);
@@ -672,7 +699,6 @@ pci_disable_device(struct pci_dev *dev)
         dev->is_busmaster = 0;
 
         pcibios_disable_device(dev);
-        dev->is_enabled = 0;
 }
 
 /**
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 6bf327db5c5e..398852f526a6 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -1,5 +1,6 @@
 /* Functions internal to the PCI core code */
 
+extern int __must_check __pci_enable_device(struct pci_dev *);
 extern int pci_uevent(struct device *dev, char **envp, int num_envp,
                       char *buffer, int buffer_size);
 extern int pci_create_sysfs_dev_files(struct pci_dev *pdev);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 09be0f81b27b..01c707261f9c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -51,6 +51,7 @@
 #include <linux/list.h>
 #include <linux/compiler.h>
 #include <linux/errno.h>
+#include <asm/atomic.h>
 #include <linux/device.h>
 
 /* File state for mmap()s on /proc/bus/pci/X/Y */
@@ -159,7 +160,6 @@ struct pci_dev {
         unsigned int    transparent:1;  /* Transparent PCI bridge */
         unsigned int    multifunction:1;/* Part of multi-function device */
         /* keep track of device state */
-        unsigned int    is_enabled:1;   /* pci_enable_device has been called */
         unsigned int    is_busmaster:1; /* device is busmaster */
         unsigned int    no_msi:1;       /* device may not use msi */
         unsigned int    no_d1d2:1;   /* only allow d0 or d3 */
@@ -167,6 +167,7 @@ struct pci_dev {
         unsigned int    broken_parity_status:1; /* Device generates false positive parity */
         unsigned int    msi_enabled:1;
         unsigned int    msix_enabled:1;
+        atomic_t        enable_cnt;     /* pci_enable_device has been called */
 
         u32             saved_config_space[16]; /* config space saved at suspend time */
         struct hlist_head saved_cap_space;