PCI/bwctrl: Disable BW controller on Intel P45 using a quirk

The commit 665745f27487 ("PCI/bwctrl: Re-add BW notification portdrv as
PCIe BW controller") was found to lead to a boot hang on a Intel P45
system. Testing without setting Link Bandwidth Management Interrupt Enable
(LBMIE) and Link Autonomous Bandwidth Interrupt Enable (LABIE) (PCIe r7.0,
sec 7.5.3.7) in bwctrl allowed system to come up.

P45 is a very old chipset and supports only up to gen2 PCIe, so not having
bwctrl does not seem a huge deficiency.

Add no_bw_notif in struct pci_dev and quirk Intel P45 Root Port with it.

Reported-by: Adam Stylinski <kungfujesus06@gmail.com>
Link: https://lore.kernel.org/linux-pci/aUCt1tHhm_-XIVvi@eggsbenedict/
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Adam Stylinski <kungfujesus06@gmail.com>
Link: https://patch.msgid.link/20260116131513.2359-1-ilpo.jarvinen@linux.intel.com

diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 36f939f23d34e8a3b25a2d1b9059e015f298ca94..4ae92c9f912a8b2d57ccfa60a16e2cae131ba757 100644 (file)
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -250,6 +250,9 @@ static int pcie_bwnotif_probe(struct pcie_device *srv)
        struct pci_dev *port = srv->port;
        int ret;
 
+       if (port->no_bw_notif)
+               return -ENODEV;
+
        /* Can happen if we run out of bus numbers during enumeration. */
        if (!port->subordinate)
                return -ENODEV;

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index b9c252aa6fe08a864cebe245f5dd7bf41fcc5116..6ef42a2c48318c8e214a08784c299e6e4ad27c4d 100644 (file)
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -1359,6 +1359,16 @@ static void quirk_transparent_bridge(struct pci_dev *dev)
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,  PCI_DEVICE_ID_INTEL_82380FB,    quirk_transparent_bridge);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_TOSHIBA,        0x605,  quirk_transparent_bridge);
 
+/*
+ * Enabling Link Bandwidth Management Interrupts (BW notifications) can cause
+ * boot hangs on P45.
+ */
+static void quirk_p45_bw_notifications(struct pci_dev *dev)
+{
+       dev->no_bw_notif = 1;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2e21, quirk_p45_bw_notifications);
+
 /*
  * Common misconfiguration of the MediaGX/Geode PCI master that will reduce
  * PCI bandwidth from 70MB/s to 25MB/s.  See the GXM/GXLV/GX1 datasheets

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 864775651c6fae125972cdfb062fd4d684cf294c..3a556cd749e32f2c779e99def0a76d5d4b058637 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -406,6 +406,7 @@ struct pci_dev {
                                                      user sysfs */
        unsigned int    clear_retrain_link:1;   /* Need to clear Retrain Link
                                                   bit manually */
+       unsigned int    no_bw_notif:1;  /* BW notifications may cause issues */
        unsigned int    d3hot_delay;    /* D3hot->D0 transition time in ms */
        unsigned int    d3cold_delay;   /* D3cold->D0 transition time in ms */