phb4: set PBCQ Tunnel BAR for tunneled operations

P9 supports PCI tunneled operations (atomics and as_notify) that are
initiated by devices.

A subset of the tunneled operations require a response, that must be
sent back from the host to the device. For example, an atomic compare
and swap will return the compare status, as swap will only performed
in case of success.  Similarly, as_notify reports if the target thread
has been woken up or not, because the operation may fail.

To enable tunneled operations, a device driver must tell the host where
it expects tunneled operation responses, by setting the PBCQ Tunnel BAR
Response register with a specific value within the range of its BARs.

This register is currently initialized by enable_capi_mode(). But, as
tunneled operations may also operate in PCI mode, a new API is required
to set the PBCQ Tunnel BAR Response register, without switching to CAPI
mode.

This patch provides two new OPAL calls to get/set the PBCQ Tunnel
BAR Response register.

Note: as there is only one PBCQ Tunnel BAR register, shared between
all the devices connected to the same PHB, only one of these devices
will be able to use tunneled operations, at any time.

Signed-off-by: Philippe Bergheaud <felix@linux.vnet.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

0 files changed, 0 insertions, 0 deletions