Re: PCIe MSI support

[Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>]

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* Olof Johansson wrote:
> Hi,
> 
> On Thu, Nov 24, 2011 at 11:57 AM, Thierry Reding
> <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org> wrote:
> > Hi,
> >
> > I was wondering whether anyone had gotten MSI to work with Tegra2? The code
> > in arch/arm/mach-tegra/pcie.c has some comments saying that it currently
> > isn't supported.
> >
> > Looking through the Tegra2 TRM didn't show much related to MSI. In particular
> > there doesn't seem to be any mention of the AFI controller or any of it's
> > registers (except of how to enable/disable the AFI clock or reset the
> > controller).
> >
> > Furthermore I wasn't able to get PCIe to work on Harmony with a mainline
> > kernel. Is something missing or am I just doing something wrong?
> 
> I think there might be an issue with regulator setup for pci-e, I got
> a vague bug report off-list from someone about it but I'm normally not
> using devices with pci-e on them myself.

I've verified with a hardware engineer that the voltages indeed seem correct.
Even the PCIe reference clock can be measured at the mini-PCIe connectors. So
something must be going right.

> Note that trimslice does enable pci-e, so you can use that for comparison.

Trimslice doesn't seem to do much regarding PCIe initialization. It basically
just calls the tegra_pcie_init() and has the pinmuxing set up via the pinmux
table as opposed to Harmony.

I'm thinking about ordering a Trimslice to use for comparison. Has anyone
else verified that mainline has working PCIe for Trimslice? I think Mike
Rapoport is no longer a regular on this list. His last commits seem to
indicate that PCIe was working on Harmony as well at the time, so I'm a
little confused about what might have happened since then.

> > I can make
> > it work with the Vibrante kernel, but that doesn't have MSI support either.
> > Since we're looking at designing an evaluation board with PCIe support I'm
> > very interested in seeing this supported in mainline. If there's anything I
> > can do to help, please let me know. Also if anyone can provide more insight
> > than the TRM, that would be great.
> 
> I have no idea if MSI is supported or not. You are aware of the errata
> list for PCI-e on Tegra though, right? You might want to consider the
> implications of said problems before you decide to use PCI-e on a
> product.

Yes, I am aware of it. The problems shouldn't be show-stoppers, though.

> On more MSI details; I suggest you try to get access to internal
> information through your Nvidia FAE -- I don't have any more
> information on it than you do but if I wanted to find out that is the
> route I would take myself.

I did that and our FAE is now trying to make documentation available
regarding the AFI controller and MSI initialization.

Thanks,
Thierry

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