[PATCH] PCI: pciehp: Add PLX quirk for missing Command Completed events

[PATCH] PCI: pciehp: Add PLX 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.

This behavior exactly matches the conditions described when
quirk_cmd_compl() was first added: both controllers 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@arista.com>
---
 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..5450aa6c7 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, 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);
+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);

base-commit: 5dd1818b15d98d4a20806cd00b1b40320b06004f
-- 
2.51.0

Re: [PATCH] PCI: pciehp: Add PLX quirk for missing Command Completed events

[sashiko-bot]

> 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.
> 
> This behavior exactly matches the conditions described when
> quirk_cmd_compl() was first added: both controllers 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@arista.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260918211926.1480-1-yurypm@arista.com?part=1