phb4: Enable PCI peer-to-peer

P9 supports PCI peer-to-peer: a PCI device can write directly to the
mmio space of another PCI device. It completely by-passes the CPU.

It requires some configuration on the PHBs involved:

1. on the initiating side, the address for the read/write operation is
in the mmio space of the target, i.e. well outside the range normally
allowed. So we disable range-checking on the TVT entry in bypass mode.

2. on the target side, we need to explicitly enable p2p by setting a
bit in a configuration register. It has the side-effect of reserving
an outbound (as seen from the CPU) store queue for p2p. Therefore we
only enable p2p on the PHBs using it, as we don't want to waste the
resource if we don't have to.

P9 supports p2p mmio writes. Reads are currently only supported if the
two devices are under the same PHB but that is expected to change in
the future, and it raises questions about intermediate switches
configuration, so we report an error for the time being.

The patch adds a new OPAL call to allow the OS to declare a p2p
(initiator, target) pair.

Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/doc/opal-api/opal-pci-set-p2p-157.rst b/doc/opal-api/opal-pci-set-p2p-157.rst
new file mode 100644
index 0000000..c34630c
--- /dev/null
+++ b/doc/opal-api/opal-pci-set-p2p-157.rst
@@ -0,0 +1,50 @@
+OPAL_PCI_SET_P2P
+================
+::
+
+   #define OPAL_PCI_SET_P2P			157
+
+   int64_t opal_pci_set_p2p(uint64_t phbid_init, uint64_t phbid_target,
+				uint64_t desc, uint16_t pe_number)
+
+   /* PCI p2p descriptor */
+   #define OPAL_PCI_P2P_ENABLE		0x1
+   #define OPAL_PCI_P2P_LOAD		0x2
+   #define OPAL_PCI_P2P_STORE		0x4
+
+The host calls this function to enable PCI peer-to-peer on the PHBs.
+
+Parameters
+----------
+::
+
+   uint64_t phbid_init
+   uint64_t phbid_target
+   uint64_t desc
+   uint16_t pe_number
+
+
+``phbid_init``
+  is the value from the PHB node ibm,opal-phbid property for the device initiating the p2p operation
+
+``phbid_target``
+  is the value from the PHB node ibm,opal-phbid property for the device targeted by the p2p operation
+
+``desc``
+  tells whether the p2p operation is a store (OPAL_PCI_P2P_STORE) or load (OPAL_PCI_P2P_LOAD). Can be both.
+  OPAL_PCI_P2P_ENABLE enables/disables the setting
+
+``pe_number``
+  PE number for the initiating device
+
+Return Values
+-------------
+
+``OPAL_SUCCESS``
+  Configuration was successful
+
+``OPAL_PARAMETER``
+  Invalid PHB or mode parameter
+
+``OPAL_UNSUPPORTED``
+  Not supported by hardware