[Nouveau] known MSI errata?

[Ben Skeggs]

On Fri, Oct 25, 2013 at 9:10 AM, Robert Morell <rmorell at nvidia.com> wrote:
> On Thu, Oct 24, 2013 at 04:03:12PM -0700, Ben Skeggs wrote:
>> On Fri, Oct 25, 2013 at 7:43 AM, Robert Morell <rmorell at nvidia.com> wrote:
>> > On Mon, Sep 30, 2013 at 10:44:12AM -0700, Lucas Stach wrote:
>> >> Hi,
>> >>
>> >> recently we tried to enable MSI interrupts with nouveau. Unfortunately
>> >> there have been some reports of things failing with certain cards, where
>> >> it isn't entirely clear if this is a GPU errata or some other component
>> >> in the PCIe chain failing.
>> >>
>> >> Could you perhaps investigate if there are any known Nvidia GPU erratas
>> >> with regard to MSI interrupts, or maybe tell us the generations of cards
>> >> that are generally safe to enable MSIs with?
>> >
>> > Sorry for the slow reply, Lucas.
>> >
>> > We enabled MSI interrupts by default relatively recently in the proprietary
>> > driver (version 325.08, released 2013-07-01 according to our public
>> > changelog).  This was enabled across the board for all of the GPUs supported
>> > by the latest release series, so NV50 and up.  We believe it should be safe to
>> > enable MSI on those GPUs.  We never enabled MSI by default on earlier GPUs so
>> > I can't comment there.
>> >
>> > I investigated our internal documentation and source code, and found a couple
>> > of things that are probably interesting to you:
>> > - For all pre-Fermi GPUs, we use a write through PCI config space to the "EOI"
>> >   register to rearm the MSI interrupt after servicing it, rather than a write
>> >   through the MMIO pcicfg shadow region in the GPU's PCI BAR0 window at offset
>> >   0x88000.  (This was actually originally implemented for NV4x, so you'll
>> >   probably want to do that there as well.)
>> Hm, I recently discovered this while looking for the errata myself,
>> but it seems you guys only do it on G80/G84/G86, and use 0x88068 at
>> some point after that, before Fermi (G96/GT200, for example).
>
> Yes, you're right; I was reading this wrong.  The config space path
> described above is used on G8x and G92.  Newer GPUs (other than GF100
> and GF104 as mentioned previously) use the "normal" path.
Ah, excellent.  I probably should've guessed G92 would be involved here too.

Thanks again,
Ben.

>
> - Robert