[Skiboot] [PATCH v3 2/2] phb4: set PBCQ Tunnel BAR for tunneled operations

[Philippe Bergheaud]

On 15/12/2017 14:40, Philippe Bergheaud wrote:
> 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 at linux.vnet.ibm.com>
> ---
> Changelog:
>
> v2: Adjust new OPAL call numbers.
>
> v3: Rebase on skiboot 5.9.6.
>      Document new OPAL calls in doc/opal-api.
>
Linux patch:
https://patchwork.ozlabs.org/patch/849166/