Unverified Commit 360c400d authored by Shin'ichiro Kawasaki's avatar Shin'ichiro Kawasaki Committed by Ilpo Järvinen
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p2sb: Do not scan and remove the P2SB device when it is unhidden 



When drivers access P2SB device resources, it calls p2sb_bar(). Before
the commit 5913320e ("platform/x86: p2sb: Allow p2sb_bar() calls
during PCI device probe"), p2sb_bar() obtained the resources and then
called pci_stop_and_remove_bus_device() for clean up. Then the P2SB
device disappeared. The commit 5913320e introduced the P2SB device
resource cache feature in the boot process. During the resource cache,
pci_stop_and_remove_bus_device() is called for the P2SB device, then the
P2SB device disappears regardless of whether p2sb_bar() is called or
not. Such P2SB device disappearance caused a confusion [1]. To avoid the
confusion, avoid the pci_stop_and_remove_bus_device() call when the BIOS
does not hide the P2SB device.

For that purpose, cache the P2SB device resources only if the BIOS hides
the P2SB device. Call p2sb_scan_and_cache() only if p2sb_hidden_by_bios
is true. This allows removing two branches from p2sb_scan_and_cache().
When p2sb_bar() is called, get the resources from the cache if the P2SB
device is hidden. Otherwise, read the resources from the unhidden P2SB
device.

Reported-by: default avatarDaniel Walker (danielwa) <danielwa@cisco.com>
Closes: https://lore.kernel.org/lkml/ZzTI+biIUTvFT6NC@goliath/

 [1]
Fixes: 5913320e ("platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe")
Signed-off-by: default avatarShin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: default avatarHans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20241128002836.373745-5-shinichiro.kawasaki@wdc.com


Reviewed-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
parent 0286070c

drivers/platform/x86/p2sb.c

+33 −9
Original line number Diff line number Diff line
@@ -101,9 +101,7 @@ static int p2sb_scan_and_cache(struct pci_bus *bus, unsigned int devfn) 
	/*

	 * The BIOS prevents the P2SB device from being enumerated by the PCI

	 * subsystem, so we need to unhide and hide it back to lookup the BAR.

	 * Unhide the P2SB device here, if needed.

	 */

	if (p2sb_hidden_by_bios)

	pci_bus_write_config_dword(bus, devfn, P2SBC, 0);



	/* Scan the P2SB device and cache its BAR0 */
@@ -113,8 +111,6 @@ static int p2sb_scan_and_cache(struct pci_bus *bus, unsigned int devfn) 
	if (devfn == P2SB_DEVFN_GOLDMONT)

		p2sb_scan_and_cache_devfn(bus, SPI_DEVFN_GOLDMONT);



	/* Hide the P2SB device, if it was hidden */

	if (p2sb_hidden_by_bios)

	pci_bus_write_config_dword(bus, devfn, P2SBC, P2SBC_HIDE);



	if (!p2sb_valid_resource(&p2sb_resources[PCI_FUNC(devfn)].res))
@@ -142,7 +138,7 @@ static int p2sb_cache_resources(void) 
	u32 value = P2SBC_HIDE;

	struct pci_bus *bus;

	u16 class;

	int ret;

	int ret = 0;



	/* Get devfn for P2SB device itself */

	p2sb_get_devfn(&devfn_p2sb);
@@ -168,6 +164,11 @@ static int p2sb_cache_resources(void) 
	pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);

	p2sb_hidden_by_bios = value & P2SBC_HIDE;



	/*

	 * If the BIOS does not hide the P2SB device then its resources

	 * are accesilble. Cache them only if the P2SB device is hidden.

	 */

	if (p2sb_hidden_by_bios)

		ret = p2sb_scan_and_cache(bus, devfn_p2sb);



	pci_unlock_rescan_remove();
@@ -191,6 +192,26 @@ static int p2sb_read_from_cache(struct pci_bus *bus, unsigned int devfn, 
	return 0;

}



static int p2sb_read_from_dev(struct pci_bus *bus, unsigned int devfn,

			      struct resource *mem)

{

	struct pci_dev *pdev;

	int ret = 0;



	pdev = pci_get_slot(bus, devfn);

	if (!pdev)

		return -ENODEV;



	if (p2sb_valid_resource(pci_resource_n(pdev, 0)))

		p2sb_read_bar0(pdev, mem);

	else

		ret = -ENOENT;



	pci_dev_put(pdev);



	return ret;

}



/**

 * p2sb_bar - Get Primary to Sideband (P2SB) bridge device BAR

 * @bus: PCI bus to communicate with
@@ -214,7 +235,10 @@ int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem) 
	if (!devfn)

		p2sb_get_devfn(&devfn);



	if (p2sb_hidden_by_bios)

		return p2sb_read_from_cache(bus, devfn, mem);



	return p2sb_read_from_dev(bus, devfn, mem);

}

EXPORT_SYMBOL_GPL(p2sb_bar);