We use list_is_singular() to identify the slot whether is
only slot directly connected to the root port in
pcie_find_smpss(). It's not correct, if we have only slot
connected to root port, and this slot has two function devices.
list_is_singular() return false. This patch introduces
pci_only_one_slot() to fix this issue. In addition, we should
pass subordinate bus devices list to list_is_singular(), not
its parent bus devices list.
-+-[0000:40]-+-00.0-[0000:41]--
......................
| +-07.0-[0000:46]--+-00.0 Intel Corporation 82576 Gigabit Network
Connection
| | \-00.1 Intel Corporation 82576 Gigabit Network
Connection
MPS configure after boot up, with boot command "pci=pcie_bus_safe"
linux-ha2:~ # lspci -vvv -s 40:07.0
40:07.0 PCI bridge: Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root
Port 7 (rev 22) (prog-if 00 [Normal decode])
...............
Capabilities: [90] Express (v2) Root Port (Slot+), MSI 00
DevCap: MaxPayload 256 bytes, PhantFunc 0, Latency L0s <64ns,
L1 <1us
ExtTag+ RBE+ FLReset-
DevCtl: Report errors: Correctable+ Non-Fatal+ Fatal+
Unsupported+
RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
MaxPayload 256 bytes, MaxReadReq 128 bytes
linux-ha2:~ # lspci -vvv -s 46:00.0
46:00.0 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection
(rev 01)
...............
Capabilities: [a0] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s <512ns,
L1 <64us
ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset+
DevCtl: Report errors: Correctable+ Non-Fatal+ Fatal+
Unsupported+
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ FLReset-
MaxPayload 256 bytes, MaxReadReq 512 bytes
linux-ha2:/sys/bus/pci/slots/7 # echo 0 > power ------>power off slot
linux-ha2:/sys/bus/pci/slots/7 # echo 1 > power ------>power on slot
linux-ha2:/sys/bus/pci/slots/7 # dmesg
................
pcieport 0000:40:07.0: PCI-E Max Payload Size set to 128/ 256 (was 256), Max
Read Rq 128
pci 0000:46:00.0: PCI-E Max Payload Size set to 128/ 512 (was 128), Max Read
Rq 512
pci 0000:46:00.1: PCI-E Max Payload Size set to 128/ 512 (was 128), Max Read
Rq 512
pcieport 0000:40:07.0: PCI-E Max Payload Size set to 128/ 256 (was 128), Max
Read Rq 128
pci 0000:46:00.0: PCI-E Max Payload Size set to 128/ 512 (was 128), Max Read
Rq 512
pci 0000:46:00.1: PCI-E Max Payload Size set to 128/ 512 (was 128), Max Read
Rq 512
.....
Because 46:00.0 and 46:00.1 function devices are directly connected to root
port 40:07.0.
After slot hot plug, root port mps is 256, slot fun devices(46:00.0/1) mps is
128.
We should both change root port and slot mps to 256, but now kernel change mps
to 128.
After applied this patch, dmesg after hot plug:
..............
pcieport 0000:40:07.0: PCI-E Max Payload Size set to 256/ 256 (was 256), Max
Read Rq 128
pci 0000:46:00.0: PCI-E Max Payload Size set to 256/ 512 (was 128), Max Read
Rq 512
pci 0000:46:00.1: PCI-E Max Payload Size set to 256/ 512 (was 128), Max Read
Rq 512
pcieport 0000:40:07.0: PCI-E Max Payload Size set to 256/ 256 (was 256), Max
Read Rq 128
pci 0000:46:00.0: PCI-E Max Payload Size set to 256/ 512 (was 256), Max Read
Rq 512
pci 0000:46:00.1: PCI-E Max Payload Size set to 256/ 512 (was 256), Max Read
Rq 512
Signed-off-by: Yijing Wang <[email protected]>
Cc: Jon Mason <[email protected]>
Cc: [email protected] # 3.4+
---
drivers/pci/probe.c | 20 +++++++++++++++++++-
1 files changed, 19 insertions(+), 1 deletions(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index cf57fe7..0699ec0 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1484,6 +1484,24 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
return nr;
}
+static bool pci_only_one_slot(struct pci_bus *pbus)
+{
+ u8 device;
+ struct pci_dev *pdev;
+
+ if (!pbus || list_empty(&pbus->devices))
+ return false;
+
+ pdev = list_entry(pbus->devices.next,
+ struct pci_dev, bus_list);
+ device = PCI_SLOT(pdev->devfn);
+ list_for_each_entry(pdev, &pbus->devices, bus_list)
+ if (PCI_SLOT(pdev->devfn) != device)
+ return false;
+
+ return true;
+}
+
static int pcie_find_smpss(struct pci_dev *dev, void *data)
{
u8 *smpss = data;
@@ -1506,7 +1524,7 @@ static int pcie_find_smpss(struct pci_dev *dev, void
*data)
* common case), then this is not an issue and MPS discovery
* will occur as normal.
*/
- if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
+ if (dev->is_hotplug_bridge && (!pci_only_one_slot(dev->subordinate) ||
(dev->bus->self &&
pci_pcie_type(dev->bus->self) != PCI_EXP_TYPE_ROOT_PORT)))
*smpss = 0;
--
1.7.1
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