Add pci_get_max_payload() to fetch the PCI-express maximum payload size.

Approved by:	re (gjb)
MFC after:	2 weeks
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D6951

1 files changed, 16 insertions, 0 deletions

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 06877b9..784dd00 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -1993,6 +1993,22 @@ pci_ht_map_msi(device_t dev, uint64_t addr)
 }
 
 int
+pci_get_max_payload(device_t dev)
+{
+	struct pci_devinfo *dinfo = device_get_ivars(dev);
+	int cap;
+	uint16_t val;
+
+	cap = dinfo->cfg.pcie.pcie_location;
+	if (cap == 0)
+		return (0);
+	val = pci_read_config(dev, cap + PCIER_DEVICE_CTL, 2);
+	val &= PCIEM_CTL_MAX_PAYLOAD;
+	val >>= 5;
+	return (1 << (val + 7));
+}
+
+int
 pci_get_max_read_req(device_t dev)
 {
 	struct pci_devinfo *dinfo = device_get_ivars(dev);