[PATCH v2] PCI: pciehp: Add PLX 8600/8700 quirk for missing Command Completed events

[Yury Murashka]

All PLX PEX 8600- and 8700-series data books say the Command Completed bit
is set only after the Hot Plug Controller completes a command that changes
the Attention Indicator Control, Power Indicator Control, Power Controller
Control, or Electromechanical Interlock Control fields.  It is not set
after writes that only change the Presence Detect Changed Enable or Command
Completed Interrupt Enable bits.

Consequently, pciehp waits for Command Completed after changing these
notification Enable bits and logs a timeout, for example:

  pcieport 0000:90:02.0: pciehp: Timeout on hotplug command 0x07c0
  (issued 2032 msec ago)

Like the controllers already handled by quirk_cmd_compl(), these PLX
switches report completion only when the same four Control fields change
and fail to report completion for notification Enable-only writes.

Add only the PLX PEX 8600- and 8700-series switches on which this fix was
tested to quirk_cmd_compl().  This makes pciehp mark Enable-only writes
complete immediately while continuing to wait for commands that change
Control fields.

Signed-off-by: Yury Murashka <yurypm@xxxxxxxxxx>
---
Changes in v2:
- Mention the PLX 8600/8700 series in the subject.
- Include an example of the hotplug command timeout.
- List the PLX device IDs in ascending order.
- Clarify the comparison with existing quirks and wrap the log example.
- Base the patch on the PCI maintainer tree's next branch.

Base tree: https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git (next)

 drivers/pci/hotplug/pciehp_hpc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 4c62140a3..e48e140ba 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -1122,3 +1122,17 @@ DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_QCOM, 0x0401,
 			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
 DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_HXT, 0x0401,
 			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8604,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8608,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8609,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8614,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8717,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8725,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_PLX, 0x8749,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);

base-commit: 732c4f7d2c04f8c175d85d9243213783ee024ebc
-- 
2.51.0