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p2sb: Do not scan and remove the P2SB device when it is unhidden

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BugLink: https://bugs.launchpad.net/bugs/2102266

[ Upstream commit 360c400d0f568636c1b98d1d5f9f49aa3d420c70 ]

When drivers access P2SB device resources, it calls p2sb_bar(). Before
the commit 5913320eb0 ("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 5913320eb0 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: Daniel Walker (danielwa) <danielwa@cisco.com>
Closes: https://lore.kernel.org/lkml/ZzTI+biIUTvFT6NC@goliath/ [1]
Fixes: 5913320eb0 ("platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20241128002836.373745-5-shinichiro.kawasaki@wdc.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>
This commit is contained in:
Shin'ichiro Kawasaki
2025-03-14 12:03:09 +09:00
committed by Mehmet Basaran
parent 6932a1e485
commit 29240c8a04
1 changed files with 33 additions and 9 deletions
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drivers/platform/x86/p2sb.c
+33 -9
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@@ -100,10 +100,8 @@ 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);
pci_bus_write_config_dword(bus, devfn, P2SBC, 0);
/* Scan the P2SB device and cache its BAR0 */
p2sb_scan_and_cache_devfn(bus, devfn);
@@ -112,9 +110,7 @@ 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);
pci_bus_write_config_dword(bus, devfn, P2SBC, P2SBC_HIDE);
if (!p2sb_valid_resource(&p2sb_resources[PCI_FUNC(devfn)].res))
return -ENOENT;
@@ -141,7 +137,7 @@ 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);
@@ -167,7 +163,12 @@ static int p2sb_cache_resources(void)
pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);
p2sb_hidden_by_bios = value & P2SBC_HIDE;
ret = p2sb_scan_and_cache(bus, devfn_p2sb);
/*
* 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();
@@ -190,6 +191,26 @@ 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
@@ -213,7 +234,10 @@ int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
if (!devfn)
p2sb_get_devfn(&devfn);
return p2sb_read_from_cache(bus, devfn, mem);
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);