On Mon, Sep 25, 2017 at 10:44:29AM +0530, vidya sagar wrote:
> Inline...
>
> On Sat, Sep 23, 2017 at 11:47 AM, Thierry Reding
> <thierry.reding@xxxxxxxxx> wrote:
> >
> > The Tegra20 PCIe controller has a different address range for MSI, so
> > select a different target address.
> >
> > Fixes: d7bd554f27c9 ("PCI: tegra: Do not allocate MSI target memory")
> > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> > ---
> > drivers/pci/host/pci-tegra.c | 12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> > index e8e1ddbaabc9..5b02ea59524b 100644
> > --- a/drivers/pci/host/pci-tegra.c
> > +++ b/drivers/pci/host/pci-tegra.c
> > @@ -1563,8 +1563,18 @@ static int tegra_pcie_enable_msi(struct tegra_pcie *pcie)
> > * none of the Tegra SoCs that contain this PCI host bridge can
> > * address more than 16 GiB of system memory, the last 4 KiB of
> > * these 1012 GiB is a good candidate.
> > + *
> > + * Unfortunately, Tegra20 is slightly different in that the physical
> > + * address for this MSI region is limited to the lower 32 bits of the
> > + * address map, so the address that we pick is going to have to be
> > + * located somewhere within the region addressable by the CPU and
> > + * on-SoC controllers. To be on the safe side, we select an address
> > + * from a region that is marked unused (0xf0010000 - 0xfffeffff).
> > */
> > - msi->phys = 0xfcfffff000;
> > + if (soc->msi_base_shift > 0)
> > + msi->phys = 0xfcfffff000;
> > + else
> > + msi->phys = 0x00f0010000;
>
> Can we use this for later Tegra chip versions as well?
> Reason being, if an end point's config space says that it cannot
> support >32-bit MSI addresses (Marvel SATA controller being one
> example), with the current code, we still allocate an address of
> >32-bits, resulting in end point not being able to generate MSI
> interrupt (as it discards >32-bits where generating upstream memory
> write transaction for MSI)
I hadn't considered this case. My recollection was that the PCI express
specification required every endpoint to support 64-bit MSI, but looking
again, legacy endpoints are allowed to support 32-bit MSI only, and we
could technically have one of those connected via a PCI-to-PCIe bridge.
The reason I chose 0xf0010000 for Tegra20 is because that is part of a
region that has never been used. For Tegra30 and later that address is
within the address range of system memory.
Testing has shown that the memory at the destination address isn't
actually written (the PCI host bridge seems to decode the address and
notice that it is the MSI target address and not commit the data to
memory), so technically it shouldn't matter what address we use. I'm
somewhat reluctant to use a random address, though, because having it
point to something within system memory could get confusing (if that
address shows up somewhere, how are people supposed to know this has
to do with MSI?).
Another possibility would be to use some address from within the PCIe
controller's address space that is unused. We have the following as the
current mappings:
Tegra186:
0x10000000-0x10000fff port 0 configuration space
0x10001000-0x10001fff port 1 configuration space
0x10003000-0x100037ff PADS registers
0x10003800-0x10003fff AFI registers
0x10004000-0x10004fff port 2 configuration space
0x40000000-0x4fffffff configuration space
0x50000000-0x5000ffff downstream I/O
0x50100000-0x57ffffff non-prefetchable memory
0x58000000-0x7fffffff prefetchable memory
Tegra210 and Tegra124:
0x01000000-0x01000fff port 0 configuration space
0x01001000-0x01001fff port 1 configuration space
0x01003000-0x010037ff PADS registers
0x01003800-0x01003fff AFI registers
0x02000000-0x11ffffff configuration space
0x12000000-0x1200ffff downstream I/O
0x13000000-0x1fffffff non-prefetchable memory
0x20000000-0x3fffffff prefetchable memory
Tegra30:
0x00000000-0x00000fff port 0 configuration space
0x00001000-0x00001fff port 1 configuration space
0x00003000-0x000037ff PADS registers
0x00003800-0x00003fff AFI registers
0x00004000-0x00004fff port 2 configuration space
0x02000000-0x0200ffff downstream I/O
0x10000000-0x1fffffff configuration space
0x20000000-0x27ffffff non-prefetchable memory
0x28000000-0x3fffffff prefetchable memory
Tegra20:
0x80000000-0x80000fff port 0 configuration space
0x80001000-0x80001fff port 1 configuration space
0x80003000-0x800037ff PADS registers
0x80003800-0x80003fff AFI registers
0x82000000-0x8200ffff downstream I/O
0x90000000-0x9fffffff configuration space
0xa0000000-0xa07fffff non-prefetchable memory
0xa8000000-0xbfffffff prefetchable memory
Something like the following might work as MSI target addresses, though
I haven't tested that these actually work as expected:
Tegra186: 0x10fff000-0x10ffffff
Tegra210: 0x01fff000-0x01ffffff
Tegra124: 0x01fff000-0x01ffffff
Tegra30: 0x01fff000-0x01ffffff
Tegra20: 0x81fff000-0x81ffffff
Any thought on that?
Thierry
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