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

3 files changed, 31 insertions, 1 deletions

diff --git a/share/man/man9/pci.9 b/share/man/man9/pci.9
index 52df250..a53f971 100644
--- a/share/man/man9/pci.9
+++ b/share/man/man9/pci.9
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 16, 2016
+.Dd June 24, 2016
 .Dt PCI 9
 .Os
 .Sh NAME
@@ -44,6 +44,7 @@
 .Nm pci_find_htcap ,
 .Nm pci_find_pcie_root_port ,
 .Nm pci_get_id ,
+.Nm pci_get_max_payload ,
 .Nm pci_get_max_read_req ,
 .Nm pci_get_powerstate ,
 .Nm pci_get_vpd_ident ,
@@ -100,6 +101,8 @@
 .Ft int
 .Fn pci_get_id "device_t dev" "enum pci_id_type type" "uintptr_t *id"
 .Ft int
+.Fn pci_get_max_payload "device_t dev"
+.Ft int
 .Fn pci_get_max_read_req "device_t dev"
 .Ft int
 .Fn pci_get_powerstate "device_t dev"
@@ -461,6 +464,16 @@ or
 .Xr bus_activate_resource 9 .
 .Pp
 The
+.Fn pci_get_max_payload
+function returns the current maximum TLP payload size in bytes for a
+PCI-express device.
+If the
+.Fa dev
+device is not a PCI-express device,
+.Fn pci_get_max_payload
+returns zero.
+.Pp
+The
 .Fn pci_get_max_read_req
 function returns the current maximum read request size in bytes for a
 PCI-express device.
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);
diff --git a/sys/dev/pci/pcivar.h b/sys/dev/pci/pcivar.h
index 7eaf5a6..3180b4e 100644
--- a/sys/dev/pci/pcivar.h
+++ b/sys/dev/pci/pcivar.h
@@ -585,6 +585,7 @@ int	pci_msix_device_blacklisted(device_t dev);
 void	pci_ht_map_msi(device_t dev, uint64_t addr);
 
 device_t pci_find_pcie_root_port(device_t dev);
+int	pci_get_max_payload(device_t dev);
 int	pci_get_max_read_req(device_t dev);
 void	pci_restore_state(device_t dev);
 void	pci_save_state(device_t dev);