linux-kernel - [PATCH v2] PCI: Mark LSI FW643 to avoid bus reset

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Date: Tue, 27 Feb 2024 13:14:18 +0000
From: Edmund Raile <edmund.raile@...ton.me>
To: helgaas@...nel.org
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, Edmund Raile <edmund.raile@...ton.me>
Subject: [PATCH v2] PCI: Mark LSI FW643 to avoid bus reset

Using LSI / Agere FW643 with vfio-pci will exhaust all
pci_reset_fn_methods, the bus reset at the end causes a broken link
only recoverable by removing power
(power-off / suspend + rescan).
Prevent this bus reset.
With this change, the device can be assigned to VMs with VFIO.
Note that it will not be reset, resulting in leaking state between VMs
and host.

Signed-off-by: Edmund Raile <edmund.raile@...ton.me>

---

I sincerely thank you for your patience and explaining
the background of pci resets which I lacked.
The commit message and comment now describe it correctly.
The comment on leaking states was added.

Usefulness:

The LSI FW643 PCIe->FireWire 800 interface may be EOL but it is
the only one that does not use a PCIe->PCI bridge.
It is reliable and enables FireWire audio interfaces to be used
on modern machines.

Virtualization allows for flexible access to professional audio
software.

It has been used in at least the following Apple machines:
MacBookPro10,1
MacBookPro9,2
MacBookPro6,2
MacBookPro5,1
Macmini6,1
Macmini3,1
iMac12,2
iMac9,1
iMac8,1

Implementation:

PCI_VENDOR_ID_ATT was reused as they are identical.

 drivers/pci/quirks.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index d797df6e5f3e..e0e4ad9e6d50 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3765,6 +3765,19 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003e, quirk_no_bus_reset);
  */
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_CAVIUM, 0xa100, quirk_no_bus_reset);

+/*
+ * Using LSI / Agere FW643 with vfio-pci will exhaust all
+ * pci_reset_fn_methods, the bus reset at the end causes a broken link
+ * only recoverable by removing power
+ * (power-off / suspend + rescan).
+ * Prevent this bus reset.
+ * With this change, the device can be assigned to VMs with VFIO.
+ * Note that it will not be reset, resulting in leaking state between VMs
+ * and host.
+ */
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATT, 0x5900, quirk_no_bus_reset);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATT, 0x5901, quirk_no_bus_reset);
+
 /*
  * Some TI KeyStone C667X devices do not support bus/hot reset.  The PCIESS
  * automatically disables LTSSM when Secondary Bus Reset is received and
-- 
2.43.0