[PATCH 02/11] PCI: pciehp: Enable Command Completed Interrupt only if supported

[Marek Behún]

From: Pali Rohár <pali at kernel.org>

The No Command Completed Support bit in the Slot Capabilities register
indicates whether Command Completed Interrupt Enable is unsupported.

We already check whether No Command Completed Support bit is set in
pcie_wait_cmd(), and do not wait in this case.

Let's not enable this Command Completed Interrupt at all if NCCS is set,
so that when users dump configuration space from userspace, the dump
does not confuse them by saying that Command Completed Interrupt is not
supported, but it is enabled.

Signed-off-by: Pali Rohár <pali at kernel.org>
Signed-off-by: Marek Behún <kabel at kernel.org>
---
Changes since batch 5:
- changed commit message, previously we wrote that the change is needed
  to fix a bug where kernel was waiting for an event which did not
  come. This turns out to be false. See
  https://lore.kernel.org/linux-pci/20220818142243.4c046c59@dellmb/T/#u
---
 drivers/pci/hotplug/pciehp_hpc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 373bb396fe22..838eb6cc3ec7 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -817,7 +817,9 @@ static void pcie_enable_notification(struct controller *ctrl)
 	else
 		cmd |= PCI_EXP_SLTCTL_PDCE;
 	if (!pciehp_poll_mode)
-		cmd |= PCI_EXP_SLTCTL_HPIE | PCI_EXP_SLTCTL_CCIE;
+		cmd |= PCI_EXP_SLTCTL_HPIE;
+	if (!pciehp_poll_mode && !NO_CMD_CMPL(ctrl))
+		cmd |= PCI_EXP_SLTCTL_CCIE;
 
 	mask = (PCI_EXP_SLTCTL_PDCE | PCI_EXP_SLTCTL_ABPE |
 		PCI_EXP_SLTCTL_PFDE |
-- 
2.35.1