| Message ID | 20120604091545.03ce738b@kryten (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Delegated to: | Michael Ellerman |
| Headers | show |
On Mon, 2012-06-04 at 09:15 +1000, Anton Blanchard wrote: > The pseries firmware currently refuses any non power of two MSI-X > request. Unfortunately most network drivers end up asking for that > because they want a power of two for RX queues and one or two extra > for everything else. > > This patch rounds up the firmware request to the next power of two > if the quota allows it. There is some chance this will result in breakage because the driver asks for N - and assumes that is what was allocated - and the device is configured for > N. But that's a hypothetical, and we know the current approach sucks because it will result in many drivers falling back to a single interrupt. I think this is the least-worst approach in light of the FW limitations, and we can always add quirks in here if we really have to. Paul is the pseries maintainer so he gets to ACK or NAK it, but from an MSI point of view it gets my +1. cheers
On Mon, 2012-06-04 at 16:43 +1000, Michael Ellerman wrote: > There is some chance this will result in breakage because the driver > asks for N - and assumes that is what was allocated - and the device is > configured for > N. We can fix that. We can whack the configuration back with N, just know that we have "allocated" > N. > But that's a hypothetical, and we know the current approach sucks > because it will result in many drivers falling back to a single > interrupt. > > I think this is the least-worst approach in light of the FW limitations, > and we can always add quirks in here if we really have to. > > Paul is the pseries maintainer so he gets to ACK or NAK it, but from an > MSI point of view it gets my +1. > Cheers, Ben.
Index: linux-build/arch/powerpc/platforms/pseries/msi.c =================================================================== --- linux-build.orig/arch/powerpc/platforms/pseries/msi.c 2012-06-03 20:49:29.082280031 +1000 +++ linux-build/arch/powerpc/platforms/pseries/msi.c 2012-06-04 09:06:55.909732276 +1000 @@ -402,6 +402,18 @@ static int rtas_setup_msi_irqs(struct pc return -EINVAL; /* + * Firmware currently refuse any non power of two allocation + * so we round up if the quota will allow it. + */ + if (type == PCI_CAP_ID_MSIX) { + int m = roundup_pow_of_two(nvec); + int quota = msi_quota_for_device(pdev, m); + + if (quota >= m) + nvec = m; + } + + /* * Try the new more explicit firmware interface, if that fails fall * back to the old interface. The old interface is known to never * return MSI-Xs.
The pseries firmware currently refuses any non power of two MSI-X request. Unfortunately most network drivers end up asking for that because they want a power of two for RX queues and one or two extra for everything else. This patch rounds up the firmware request to the next power of two if the quota allows it. Signed-off-by: Anton Blanchard <anton@samba.org> ---