Commit 0f50a49e authored Sep 15, 2017 by Bjorn Helgaas

Revert "PCI: Avoid race while enabling upstream bridges"

This reverts commit 40f11adc.

Jens found that iwlwifi firmware loading failed on a Lenovo X1 Carbon,
gen4:

  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-34.ucode failed with error -2
  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-33.ucode failed with error -2
  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-32.ucode failed with error -2
  iwlwifi 0000:04:00.0: loaded firmware version 31.532993.0 op_mode iwlmvm
  iwlwifi 0000:04:00.0: Detected Intel(R) Dual Band Wireless AC 8260, REV=0x208
  ...
  iwlwifi 0000:04:00.0: Failed to load firmware chunk!
  iwlwifi 0000:04:00.0: Could not load the [0] uCode section
  iwlwifi 0000:04:00.0: Failed to start INIT ucode: -110
  iwlwifi 0000:04:00.0: Failed to run INIT ucode: -110

He bisected it to 40f11adc ("PCI: Avoid race while enabling upstream
bridges").  Revert that commit to fix the regression.

Link: http://lkml.kernel.org/r/4bcbcbc1-7c79-09f0-5071-bc2f53bf6574@kernel.dk


Fixes: 40f11adc ("PCI: Avoid race while enabling upstream bridges")
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Srinath Mannam <srinath.mannam@broadcom.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: Luca Coelho <luca@coelho.fi>
CC: Johannes Berg <johannes@sipsolutions.net>
CC: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

parent 711aab1d

drivers/pci/pci.c

+2 −11

Original line number	Diff line number	Diff line
		@@ -52,7 +52,6 @@ static void pci_pme_list_scan(struct work_struct *work);
		static LIST_HEAD(pci_pme_list);
		static DEFINE_MUTEX(pci_pme_list_mutex);
		static DECLARE_DELAYED_WORK(pci_pme_work, pci_pme_list_scan);
		static DEFINE_MUTEX(pci_bridge_mutex);

		struct pci_pme_device {
		struct list_head list;
		@@ -1351,16 +1350,10 @@ static void pci_enable_bridge(struct pci_dev *dev)
		if (bridge)
		pci_enable_bridge(bridge);

		/*
		* Hold pci_bridge_mutex to prevent a race when enabling two
		* devices below the bridge simultaneously. The race may cause a
		* PCI_COMMAND_MEMORY update to be lost (see changelog).
		*/
		mutex_lock(&pci_bridge_mutex);
		if (pci_is_enabled(dev)) {
		if (!dev->is_busmaster)
		pci_set_master(dev);
		goto end;
		return;
		}

		retval = pci_enable_device(dev);
		@@ -1368,8 +1361,6 @@ static void pci_enable_bridge(struct pci_dev *dev)
		dev_err(&dev->dev, "Error enabling bridge (%d), continuing\n",
		retval);
		pci_set_master(dev);
		end:
		mutex_unlock(&pci_bridge_mutex);
		}

		static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
		@@ -1394,7 +1385,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
		return 0; /* already enabled */

		bridge = pci_upstream_bridge(dev);
		if (bridge && !pci_is_enabled(bridge))
		if (bridge)
		pci_enable_bridge(bridge);

		/* only skip sriov related */

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