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Subject[PATCH 5.10 126/599] PCI: pciehp: Clear cmd_busy bit in polling mode
From: Liguang Zhang <>

commit 92912b175178c7e895f5e5e9f1e30ac30319162b upstream.

Writes to a Downstream Port's Slot Control register are PCIe hotplug
"commands." If the Port supports Command Completed events, software must
wait for a command to complete before writing to Slot Control again.

pcie_do_write_cmd() sets ctrl->cmd_busy when it writes to Slot Control. If
software notification is enabled, i.e., PCI_EXP_SLTCTL_HPIE and
PCI_EXP_SLTCTL_CCIE are set, ctrl->cmd_busy is cleared by pciehp_isr().

But when software notification is disabled, as it is when pcie_init()
powers off an empty slot, pcie_wait_cmd() uses pcie_poll_cmd() to poll for
command completion, and it neglects to clear ctrl->cmd_busy, which leads to
spurious timeouts:

pcieport 0000:00:03.0: pciehp: Timeout on hotplug command 0x01c0 (issued 2264 msec ago)
pcieport 0000:00:03.0: pciehp: Timeout on hotplug command 0x05c0 (issued 2288 msec ago)

Clear ctrl->cmd_busy in pcie_poll_cmd() when it detects a Command Completed

[bhelgaas: commit log]
Fixes: a5dd4b4b0570 ("PCI: pciehp: Wait for hotplug command completion where necessary")
Signed-off-by: Liguang Zhang <>
Signed-off-by: Bjorn Helgaas <>
Reviewed-by: Lukas Wunner <>
Cc: # v4.19+
Signed-off-by: Greg Kroah-Hartman <>
drivers/pci/hotplug/pciehp_hpc.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -98,6 +98,8 @@ static int pcie_poll_cmd(struct controll
if (slot_status & PCI_EXP_SLTSTA_CC) {
pcie_capability_write_word(pdev, PCI_EXP_SLTSTA,
+ ctrl->cmd_busy = 0;
+ smp_mb();
return 1;

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