Revert "PCI: Use to_pci_driver() instead of pci_dev->driver"

This reverts commit 2a4d9408.

Robert reported a NULL pointer dereference caused by the PCI core
(local_pci_probe()) calling the i2c_designware_pci driver's
.runtime_resume() method before the .probe() method.  i2c_dw_pci_resume()
depends on initialization done by i2c_dw_pci_probe().

Prior to 2a4d9408 ("PCI: Use to_pci_driver() instead of
pci_dev->driver"), pci_pm_runtime_resume() avoided calling the
.runtime_resume() method because pci_dev->driver had not been set yet.

2a4d9408 and b5f9c644 ("PCI: Remove struct pci_dev->driver"),
removed pci_dev->driver, replacing it by device->driver, which *has* been
set by this time, so pci_pm_runtime_resume() called the .runtime_resume()
method when it previously had not.

Fixes: 2a4d9408 ("PCI: Use to_pci_driver() instead of pci_dev->driver")
Link: https://lore.kernel.org/linux-i2c/CAP145pgdrdiMAT7=-iB1DMgA7t_bMqTcJL4N0=6u8kNY3EU0dw@mail.gmail.com/Reported-by: Robert Święcki <robert@swiecki.net>
Tested-by: Robert Święcki <robert@swiecki.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/iov.c

@@ -164,15 +164,13 @@ static ssize_t sriov_vf_total_msix_show(struct device *dev,
 					char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_driver *pdrv;
 	u32 vf_total_msix = 0;
 
 	device_lock(dev);
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv || !pdrv->sriov_get_vf_total_msix)
+	if (!pdev->driver || !pdev->driver->sriov_get_vf_total_msix)
 		goto unlock;
 
-	vf_total_msix = pdrv->sriov_get_vf_total_msix(pdev);
+	vf_total_msix = pdev->driver->sriov_get_vf_total_msix(pdev);
 unlock:
 	device_unlock(dev);
 	return sysfs_emit(buf, "%u\n", vf_total_msix);
@@ -185,7 +183,6 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 {
 	struct pci_dev *vf_dev = to_pci_dev(dev);
 	struct pci_dev *pdev = pci_physfn(vf_dev);
-	struct pci_driver *pdrv;
 	int val, ret = 0;
 
 	if (kstrtoint(buf, 0, &val) < 0)
@@ -195,14 +192,13 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 		return -EINVAL;
 
 	device_lock(&pdev->dev);
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv || !pdrv->sriov_set_msix_vec_count) {
+	if (!pdev->driver || !pdev->driver->sriov_set_msix_vec_count) {
 		ret = -EOPNOTSUPP;
 		goto err_pdev;
 	}
 
 	device_lock(&vf_dev->dev);
-	if (to_pci_driver(vf_dev->dev.driver)) {
+	if (vf_dev->driver) {
 		/*
 		 * A driver is already attached to this VF and has configured
 		 * itself based on the current MSI-X vector count. Changing
@@ -212,7 +208,7 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 		goto err_dev;
 	}
 
-	ret = pdrv->sriov_set_msix_vec_count(vf_dev, val);
+	ret = pdev->driver->sriov_set_msix_vec_count(vf_dev, val);
 
 err_dev:
 	device_unlock(&vf_dev->dev);
@@ -379,7 +375,6 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 				  const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_driver *pdrv;
 	int ret = 0;
 	u16 num_vfs;
 
@@ -395,15 +390,14 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 		goto exit;
 
 	/* is PF driver loaded */
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv) {
+	if (!pdev->driver) {
 		pci_info(pdev, "no driver bound to device; cannot configure SR-IOV\n");
 		ret = -ENOENT;
 		goto exit;
 	}
 
 	/* is PF driver loaded w/callback */
-	if (!pdrv->sriov_configure) {
+	if (!pdev->driver->sriov_configure) {
 		pci_info(pdev, "driver does not support SR-IOV configuration via sysfs\n");
 		ret = -ENOENT;
 		goto exit;
@@ -411,7 +405,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 
 	if (num_vfs == 0) {
 		/* disable VFs */
-		ret = pdrv->sriov_configure(pdev, 0);
+		ret = pdev->driver->sriov_configure(pdev, 0);
 		goto exit;
 	}
 
@@ -423,7 +417,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 		goto exit;
 	}
 
-	ret = pdrv->sriov_configure(pdev, num_vfs);
+	ret = pdev->driver->sriov_configure(pdev, num_vfs);
 	if (ret < 0)
 		goto exit;
 

drivers/pci/pci-driver.c

@@ -457,7 +457,7 @@ static int pci_device_probe(struct device *dev)
 static void pci_device_remove(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	struct pci_driver *drv = to_pci_driver(dev->driver);
+	struct pci_driver *drv = pci_dev->driver;
 
 	if (drv->remove) {
 		pm_runtime_get_sync(dev);
@@ -493,7 +493,7 @@ static void pci_device_remove(struct device *dev)
 static void pci_device_shutdown(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	struct pci_driver *drv = to_pci_driver(dev->driver);
+	struct pci_driver *drv = pci_dev->driver;
 
 	pm_runtime_resume(dev);
 
@@ -589,7 +589,7 @@ static int pci_pm_reenable_device(struct pci_dev *pci_dev)
 static int pci_legacy_suspend(struct device *dev, pm_message_t state)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	struct pci_driver *drv = to_pci_driver(dev->driver);
+	struct pci_driver *drv = pci_dev->driver;
 
 	if (drv && drv->suspend) {
 		pci_power_t prev = pci_dev->current_state;
@@ -630,7 +630,7 @@ static int pci_legacy_suspend_late(struct device *dev, pm_message_t state)
 static int pci_legacy_resume(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	struct pci_driver *drv = to_pci_driver(dev->driver);
+	struct pci_driver *drv = pci_dev->driver;
 
 	pci_fixup_device(pci_fixup_resume, pci_dev);
 
@@ -649,7 +649,7 @@ static void pci_pm_default_suspend(struct pci_dev *pci_dev)
 
 static bool pci_has_legacy_pm_support(struct pci_dev *pci_dev)
 {
-	struct pci_driver *drv = to_pci_driver(pci_dev->dev.driver);
+	struct pci_driver *drv = pci_dev->driver;
 	bool ret = drv && (drv->suspend || drv->resume);
 
 	/*
@@ -1242,11 +1242,11 @@ static int pci_pm_runtime_suspend(struct device *dev)
 	int error;
 
 	/*
-	 * If the device has no driver, we leave it in D0, but it may go to
-	 * D3cold when the bridge above it runtime suspends.  Save its
-	 * config space in case that happens.
+	 * If pci_dev->driver is not set (unbound), we leave the device in D0,
+	 * but it may go to D3cold when the bridge above it runtime suspends.
+	 * Save its config space in case that happens.
 	 */
-	if (!to_pci_driver(dev->driver)) {
+	if (!pci_dev->driver) {
 		pci_save_state(pci_dev);
 		return 0;
 	}
@@ -1303,7 +1303,7 @@ static int pci_pm_runtime_resume(struct device *dev)
 	 */
 	pci_restore_standard_config(pci_dev);
 
-	if (!to_pci_driver(dev->driver))
+	if (!pci_dev->driver)
 		return 0;
 
 	pci_fixup_device(pci_fixup_resume_early, pci_dev);
@@ -1322,13 +1322,14 @@ static int pci_pm_runtime_resume(struct device *dev)
 
 static int pci_pm_runtime_idle(struct device *dev)
 {
+	struct pci_dev *pci_dev = to_pci_dev(dev);
 	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
 
 	/*
-	 * If the device has no driver, it should always remain in D0
-	 * regardless of the runtime PM status
+	 * If pci_dev->driver is not set (unbound), the device should
+	 * always remain in D0 regardless of the runtime PM status
 	 */
-	if (!to_pci_driver(dev->driver))
+	if (!pci_dev->driver)
 		return 0;
 
 	if (!pm)
@@ -1435,10 +1436,8 @@ static struct pci_driver pci_compat_driver = {
  */
 struct pci_driver *pci_dev_driver(const struct pci_dev *dev)
 {
-	struct pci_driver *drv = to_pci_driver(dev->dev.driver);
-
-	if (drv)
-		return drv;
+	if (dev->driver)
+		return dev->driver;
 	else {
 		int i;
 		for (i = 0; i <= PCI_ROM_RESOURCE; i++)

drivers/pci/pci.c

@@ -5123,14 +5123,13 @@ EXPORT_SYMBOL_GPL(pci_dev_unlock);
 
 static void pci_dev_save_and_disable(struct pci_dev *dev)
 {
-	struct pci_driver *drv = to_pci_driver(dev->dev.driver);
 	const struct pci_error_handlers *err_handler =
-			drv ? drv->err_handler : NULL;
+			dev->driver ? dev->driver->err_handler : NULL;
 
 	/*
-	 * drv->err_handler->reset_prepare() is protected against races
-	 * with ->remove() by the device lock, which must be held by the
-	 * caller.
+	 * dev->driver->err_handler->reset_prepare() is protected against
+	 * races with ->remove() by the device lock, which must be held by
+	 * the caller.
 	 */
 	if (err_handler && err_handler->reset_prepare)
 		err_handler->reset_prepare(dev);
@@ -5155,15 +5154,15 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
 
 static void pci_dev_restore(struct pci_dev *dev)
 {
-	struct pci_driver *drv = to_pci_driver(dev->dev.driver);
 	const struct pci_error_handlers *err_handler =
-			drv ? drv->err_handler : NULL;
+			dev->driver ? dev->driver->err_handler : NULL;
 
 	pci_restore_state(dev);
 
 	/*
-	 * drv->err_handler->reset_done() is protected against races with
-	 * ->remove() by the device lock, which must be held by the caller.
+	 * dev->driver->err_handler->reset_done() is protected against
+	 * races with ->remove() by the device lock, which must be held by
+	 * the caller.
 	 */
 	if (err_handler && err_handler->reset_done)
 		err_handler->reset_done(dev);

drivers/pci/pcie/err.c

@@ -54,7 +54,7 @@ static int report_error_detected(struct pci_dev *dev,
 	const struct pci_error_handlers *err_handler;
 
 	device_lock(&dev->dev);
-	pdrv = to_pci_driver(dev->dev.driver);
+	pdrv = dev->driver;
 	if (!pci_dev_set_io_state(dev, state) ||
 		!pdrv ||
 		!pdrv->err_handler ||
@@ -98,7 +98,7 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data)
 	const struct pci_error_handlers *err_handler;
 
 	device_lock(&dev->dev);
-	pdrv = to_pci_driver(dev->dev.driver);
+	pdrv = dev->driver;
 	if (!pdrv ||
 		!pdrv->err_handler ||
 		!pdrv->err_handler->mmio_enabled)
@@ -119,7 +119,7 @@ static int report_slot_reset(struct pci_dev *dev, void *data)
 	const struct pci_error_handlers *err_handler;
 
 	device_lock(&dev->dev);
-	pdrv = to_pci_driver(dev->dev.driver);
+	pdrv = dev->driver;
 	if (!pdrv ||
 		!pdrv->err_handler ||
 		!pdrv->err_handler->slot_reset)
@@ -139,7 +139,7 @@ static int report_resume(struct pci_dev *dev, void *data)
 	const struct pci_error_handlers *err_handler;
 
 	device_lock(&dev->dev);
-	pdrv = to_pci_driver(dev->dev.driver);
+	pdrv = dev->driver;
 	if (!pci_dev_set_io_state(dev, pci_channel_io_normal) ||
 		!pdrv ||
 		!pdrv->err_handler ||