Commit 51c48b31 authored by Bjorn Helgaas's avatar Bjorn Helgaas
Browse files

PCI: Probe bridge window attributes once at enumeration-time 

pci_bridge_check_ranges() determines whether a bridge supports the optional
I/O and prefetchable memory windows and sets the flag bits in the bridge
resources.  This *could* be done once during enumeration except that the
resource allocation code completely clears the flag bits, e.g., in the
pci_assign_unassigned_bridge_resources() path.

The problem with pci_bridge_check_ranges() in the resource allocation path
is that we may allocate resources after devices have been claimed by
drivers, and pci_bridge_check_ranges() *changes* the window registers to
determine whether they're writable.  This may break concurrent accesses to
devices behind the bridge.

Add a new pci_read_bridge_windows() to determine whether a bridge supports
the optional windows, call it once during enumeration, remember the
results, and change pci_bridge_check_ranges() so it doesn't touch the
bridge windows but sets the flag bits based on those remembered results.

Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html


Reported-by: default avatarYandong Xu <xuyandong2@huawei.com>
Tested-by: default avatarYandong Xu <xuyandong2@huawei.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Ofer Hayut <ofer@lightbitslabs.com>
Cc: Roy Shterman <roys@lightbitslabs.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
parent bfeffd15

drivers/pci/probe.c

+52 −0
Original line number Diff line number Diff line
@@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom) 
	}

}



static void pci_read_bridge_windows(struct pci_dev *bridge)

{

	u16 io;

	u32 pmem, tmp;



	pci_read_config_word(bridge, PCI_IO_BASE, &io);

	if (!io) {

		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);

		pci_read_config_word(bridge, PCI_IO_BASE, &io);

		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);

	}

	if (io)

		bridge->io_window = 1;



	/*

	 * DECchip 21050 pass 2 errata: the bridge may miss an address

	 * disconnect boundary by one PCI data phase.  Workaround: do not

	 * use prefetching on this device.

	 */

	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)

		return;



	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);

	if (!pmem) {

		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,

					       0xffe0fff0);

		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);

		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);

	}

	if (!pmem)

		return;



	bridge->pref_window = 1;



	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {



		/*

		 * Bridge claims to have a 64-bit prefetchable memory

		 * window; verify that the upper bits are actually

		 * writable.

		 */

		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);

		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,

				       0xffffffff);

		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);

		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);

		if (tmp)

			bridge->pref_64_window = 1;

	}

}



static void pci_read_bridge_io(struct pci_bus *child)

{

	struct pci_dev *dev = child->self;
@@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev) 
		pci_read_irq(dev);

		dev->transparent = ((dev->class & 0xff) == 1);

		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);

		pci_read_bridge_windows(dev);

		set_pcie_hotplug_bridge(dev);

		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);

		if (pos) {

drivers/pci/setup-bus.c

+4 −41
Original line number Diff line number Diff line
@@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i) 
   base/limit registers must be read-only and read as 0. */

static void pci_bridge_check_ranges(struct pci_bus *bus)

{

	u16 io;

	u32 pmem;

	struct pci_dev *bridge = bus->self;

	struct resource *b_res;

	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];



	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];

	b_res[1].flags |= IORESOURCE_MEM;



	pci_read_config_word(bridge, PCI_IO_BASE, &io);

	if (!io) {

		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);

		pci_read_config_word(bridge, PCI_IO_BASE, &io);

		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);

	}

	if (io)

	if (bridge->io_window)

		b_res[0].flags |= IORESOURCE_IO;



	/*  DECchip 21050 pass 2 errata: the bridge may miss an address

	    disconnect boundary by one PCI data phase.

	    Workaround: do not use prefetching on this device. */

	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)

		return;



	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);

	if (!pmem) {

		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,

					       0xffe0fff0);

		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);

		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);

	}

	if (pmem) {

	if (bridge->pref_window) {

		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;

		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==

		    PCI_PREF_RANGE_TYPE_64) {

		if (bridge->pref_64_window) {

			b_res[2].flags |= IORESOURCE_MEM_64;

			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;

		}

	}



	/* double check if bridge does support 64 bit pref */

	if (b_res[2].flags & IORESOURCE_MEM_64) {

		u32 mem_base_hi, tmp;

		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,

					 &mem_base_hi);

		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,

					       0xffffffff);

		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);

		if (!tmp)

			b_res[2].flags &= ~IORESOURCE_MEM_64;

		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,

				       mem_base_hi);

	}

}



/* Helper function for sizing routines: find first available

include/linux/pci.h

+3 −0
Original line number Diff line number Diff line
@@ -373,6 +373,9 @@ struct pci_dev { 
	bool		match_driver;		/* Skip attaching driver */



	unsigned int	transparent:1;		/* Subtractive decode bridge */

	unsigned int	io_window:1;		/* Bridge has I/O window */

	unsigned int	pref_window:1;		/* Bridge has pref mem window */

	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */

	unsigned int	multifunction:1;	/* Multi-function device */



	unsigned int	is_busmaster:1;		/* Is busmaster */