6.12-stable review patch. If anyone has any objections, please let me know.
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From: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com
[ Upstream commit 360c400d0f568636c1b98d1d5f9f49aa3d420c70 ]
When drivers access P2SB device resources, it calls p2sb_bar(). Before the commit 5913320eb0b3 ("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 5913320eb0b3 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: 5913320eb0b3 ("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.co... 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 --- drivers/platform/x86/p2sb.c | 42 +++++++++++++++++++++++++++++-------- 1 file changed, 33 insertions(+), 9 deletions(-)
diff --git a/drivers/platform/x86/p2sb.c b/drivers/platform/x86/p2sb.c index 0bc6b21c4c20..c56650b9ff96 100644 --- a/drivers/platform/x86/p2sb.c +++ b/drivers/platform/x86/p2sb.c @@ -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);