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 P2SB
device is hidden. When p2sb_cache_resources() is called, check if the
device is hidden and store the result in the global flag p2sb_hidden.
Check the flag in p2sb_bar() and if the device is hidden, refer to the
cached resources. Otherwise, read the resources from the unhidden P2SB
device.
Reported-by: "Daniel Walker (danielwa)" <danielwa@xxxxxxxxx>
Fixes: 5913320eb0b3 ("platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe")
Closes: https://lore.kernel.org/lkml/ZzTI+biIUTvFT6NC@goliath/ [1]
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
---
Changes from v1:
* Put back P2SBC_HIDE flag reference code in the rescan_remove lock region
* Do not cache resources when the P2SB device is not hidden
* Added the Reported-by tag
drivers/platform/x86/p2sb.c | 56 ++++++++++++++++++++++++++-----------
1 file changed, 40 insertions(+), 16 deletions(-)
diff --git a/drivers/platform/x86/p2sb.c b/drivers/platform/x86/p2sb.c
index 31f38309b389..0b1d604fcfe5 100644
--- a/drivers/platform/x86/p2sb.c
+++ b/drivers/platform/x86/p2sb.c
@@ -42,6 +42,7 @@ struct p2sb_res_cache {
};
static struct p2sb_res_cache p2sb_resources[NR_P2SB_RES_CACHE];
+static bool p2sb_hidden;
static void p2sb_get_devfn(unsigned int *devfn)
{
@@ -152,20 +153,23 @@ static int p2sb_cache_resources(void)
pci_lock_rescan_remove();
/*
- * 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.
+ * The BIOS does not hide the P2SB device then its resources are
+ * accesilble. Do not cache them.
*/
pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);
- if (value & P2SBC_HIDE)
- pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0);
+ p2sb_hidden = value & P2SBC_HIDE;
+ if (!p2sb_hidden)
+ goto unlock;
+ /*
+ * 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.
+ */
+ pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0);
ret = p2sb_scan_and_cache(bus, devfn_p2sb);
+ pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE);
- /* Hide the P2SB device, if it was hidden */
- if (value & P2SBC_HIDE)
- pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE);
-
+unlock:
pci_unlock_rescan_remove();
return ret;
@@ -188,6 +192,8 @@ static int p2sb_cache_resources(void)
int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
{
struct p2sb_res_cache *cache;
+ struct pci_dev *pdev;
+ int ret = 0;
bus = p2sb_get_bus(bus);
if (!bus)
@@ -196,15 +202,33 @@ int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
if (!devfn)
p2sb_get_devfn(&devfn);
- cache = &p2sb_resources[PCI_FUNC(devfn)];
- if (cache->bus_dev_id != bus->dev.id)
- return -ENODEV;
+ /*
+ * If the P2SB device is hidden, refer to the cached resources.
+ * Otherwise, read the resources on the fly.
+ */
+ if (p2sb_hidden) {
+ cache = &p2sb_resources[PCI_FUNC(devfn)];
+ if (cache->bus_dev_id != bus->dev.id)
+ return -ENODEV;
- if (!p2sb_valid_resource(&cache->res))
- return -ENOENT;
+ if (!p2sb_valid_resource(&cache->res))
+ return -ENOENT;
- memcpy(mem, &cache->res, sizeof(*mem));
- return 0;
+ memcpy(mem, &cache->res, sizeof(*mem));
+ } else {
+ 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;
}
EXPORT_SYMBOL_GPL(p2sb_bar);
--
2.47.0
