On Wed, Jun 12, 2019 at 1:53 AM Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > > On Tue, 2019-06-11 at 20:22 +0300, Oded Gabbay wrote: > > > > > So, to summarize: > > > If I call pci_set_dma_mask with 48, then it fails on POWER9. However, > > > in runtime, I don't know if its POWER9 or not, so upon failure I will > > > call it again with 32, which makes our device pretty much unusable. > > > If I call pci_set_dma_mask with 64, and do the dedicated configuration > > > in Goya's PCIe controller, then it won't work on x86-64, because bit > > > 59 will be set and the host won't like it (I checked it). In addition, > > > I might get addresses above 50 bits, which my device can't generate. > > > > > > I hope this makes things more clear. Now, please explain to me how I > > > can call pci_set_dma_mask without any regard to whether I run on > > > x86-64 or POWER9, considering what I wrote above ? > > > > > > Thanks, > > > Oded > > > > Adding ppc mailing list. > > You can't. Your device is broken. Devices that don't support DMAing to > the full 64-bit deserve to be added to the trash pile. > Hmm... right know they are added to customers data-centers but what do I know ;)
> As a result, getting it to work will require hacks. Some GPUs have > similar issues and require similar hacks, it's unfortunate. > > Added a couple of guys on CC who might be able to help get those hacks > right. Thanks :) > > It's still very fishy .. the idea is to detect the case where setting a > 64-bit mask will give your system memory mapped at a fixed high address > (1 << 59 in our case) and program that in your chip in the "Fixed high > bits" register that you seem to have (also make sure it doesn't affect > MSIs or it will break them). MSI-X are working. The set of bit 59 doesn't apply to MSI-X transactions (AFAICS from the PCIe controller spec we have). > > This will only work as long as all of the system memory can be > addressed at an offset from that fixed address that itself fits your > device addressing capabilities (50 bits in this case). It may or may > not be the case but there's no way to check since the DMA mask logic > won't really apply. Understood. In the specific system we are integrated to, that is the case - we have less then 48 bits. But, as you pointed out, it is not a generic solution but with my H/W I can't give a generic fit-all solution for POWER9. I'll settle for the best that I can do. > > You might want to consider fixing your HW in the next iteration... This > is going to bite you when x86 increases the max physical memory for > example, or on other architectures. Understood and taken care of. > > Cheers, > Ben. > > > >
