git: 22b9f618e873 - stable/13 - Set PCIe device's Max_Payload_Size to match PCIe root's.

[Alexander Motin]

The branch stable/13 has been updated by mav:

URL: https://cgit.FreeBSD.org/src/commit/?id=22b9f618e873140127570e629c19e25d13edc568

commit 22b9f618e873140127570e629c19e25d13edc568
Author:     Alexander Motin <mav at FreeBSD.org>
AuthorDate: 2021-04-05 14:34:40 +0000
Commit:     Alexander Motin <mav at FreeBSD.org>
CommitDate: 2021-05-05 00:53:55 +0000

    Set PCIe device's Max_Payload_Size to match PCIe root's.
    
    Usually on boot the MPS is already configured by BIOS.  But we've
    found that on hot-plug it is not true at least for our Supermicro
    X11 boards.  As result, mismatch between root's configuration of
    256 bytes and device's default of 128 bytes cause problems for some
    devices, while others seem to work fine.
    
    MFC after:      1 month
    Sponsored by:   iXsystems, Inc.
    
    (cherry picked from commit 5a898b2b78ce04d608bbaaa0813424b11f921ae7)
---
 sys/dev/pci/pci.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index d85ce5baa7bc..54d7957dcbf1 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -4267,6 +4267,45 @@ pci_create_iov_child_method(device_t bus, device_t pf, uint16_t rid,
 }
 #endif
 
+/*
+ * For PCIe device set Max_Payload_Size to match PCIe root's.
+ */
+static void
+pcie_setup_mps(device_t dev)
+{
+	struct pci_devinfo *dinfo = device_get_ivars(dev);
+	device_t root;
+	uint16_t rmps, mmps, mps;
+
+	if (dinfo->cfg.pcie.pcie_location == 0)
+		return;
+	root = pci_find_pcie_root_port(dev);
+	if (root == NULL)
+		return;
+	/* Check whether the MPS is already configured. */
+	rmps = pcie_read_config(root, PCIER_DEVICE_CTL, 2) &
+	    PCIEM_CTL_MAX_PAYLOAD;
+	mps = pcie_read_config(dev, PCIER_DEVICE_CTL, 2) &
+	    PCIEM_CTL_MAX_PAYLOAD;
+	if (mps == rmps)
+		return;
+	/* Check whether the device is capable of the root's MPS. */
+	mmps = (pcie_read_config(dev, PCIER_DEVICE_CAP, 2) &
+	    PCIEM_CAP_MAX_PAYLOAD) << 5;
+	if (rmps > mmps) {
+		/*
+		 * The device is unable to handle root's MPS.  Limit root.
+		 * XXX: We should traverse through all the tree, applying
+		 * it to all the devices.
+		 */
+		pcie_adjust_config(root, PCIER_DEVICE_CTL,
+		    PCIEM_CTL_MAX_PAYLOAD, mmps, 2);
+	} else {
+		pcie_adjust_config(dev, PCIER_DEVICE_CTL,
+		    PCIEM_CTL_MAX_PAYLOAD, rmps, 2);
+	}
+}
+
 static void
 pci_add_child_clear_aer(device_t dev, struct pci_devinfo *dinfo)
 {
@@ -4354,6 +4393,7 @@ pci_add_child(device_t bus, struct pci_devinfo *dinfo)
 	pci_cfg_restore(dev, dinfo);
 	pci_print_verbose(dinfo);
 	pci_add_resources(bus, dev, 0, 0);
+	pcie_setup_mps(dev);
 	pci_child_added(dinfo->cfg.dev);
 
 	if (pci_clear_aer_on_attach)