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

Philippe Bergheaud felix at linux.vnet.ibm.com
Wed Nov 8 00:19:59 AEDT 2017

On 02/11/2017 05:03, Benjamin Herrenschmidt wrote:
> On Thu, 2017-10-26 at 15:43 +0200, Philippe Bergheaud wrote:
>> On 23/10/2017 15:08, Philippe Bergheaud wrote:
>>> P9 supports PCI tunneled operations (atomics and as_notify) that require
>>> setting the PBCQ Tunnel BAR Response register with an address mask.
>>> This register is currently initialized by enable_capi_mode(). 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.
>>> This new API aims at letting devices drivers set the PBCQ Tunnel BAR.
>>> Compatibility with older kernel versions is made by enable_capi_mode().
>>> Signed-off-by: Philippe Bergheaud <felix at linux.vnet.ibm.com>
>>> ---
> Same comment as for patch 1.

I understand that the Tunnel BAR value is chosen by the device logic,
within the regular BARs assigned to the device at power-on (an entire
BAR, or a subset). The Tunnel BAR value is fetched by the device driver,
that passes it to skiboot, to set the PBCQ Tunnel BAR Response register.

I think that this patch is required. I cannot see how to reverse the
information flow.

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