[PATCH 6/6] drm/nouveau: use MSI interrupts

[Ben Skeggs]

On Wed, Aug 28, 2013 at 11:54 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> On Wed, Aug 28, 2013 at 3:28 AM, Lucas Stach <dev at lynxeye.de> wrote:
>> Am Mittwoch, den 28.08.2013, 17:09 +1000 schrieb Ben Skeggs:
>>> On Wed, Aug 28, 2013 at 10:00 AM, Lucas Stach <dev at lynxeye.de> wrote:
>>> > MSIs were only problematic on some old, broken chipsets. But now that we
>>> > already see systems where PCI legacy interrupts are somewhat flaky, it's
>>> > really time to move to MSIs.
>>> >
>>> > Signed-off-by: Lucas Stach <dev at lynxeye.de>
>>> > ---
>>> >  drivers/gpu/drm/nouveau/core/include/subdev/mc.h |  1 +
>>> >  drivers/gpu/drm/nouveau/core/subdev/mc/base.c    | 17 +++++++++++++++++
>>> >  2 files changed, 18 insertions(+)
>>> >
>>> > diff --git a/drivers/gpu/drm/nouveau/core/include/subdev/mc.h b/drivers/gpu/drm/nouveau/core/include/subdev/mc.h
>>> > index 9d2cd20..ce6569f 100644
>>> > --- a/drivers/gpu/drm/nouveau/core/include/subdev/mc.h
>>> > +++ b/drivers/gpu/drm/nouveau/core/include/subdev/mc.h
>>> > @@ -12,6 +12,7 @@ struct nouveau_mc_intr {
>>> >  struct nouveau_mc {
>>> >         struct nouveau_subdev base;
>>> >         const struct nouveau_mc_intr *intr_map;
>>> > +       bool use_msi;
>>> >  };
>>> >
>>> >  static inline struct nouveau_mc *
>>> > diff --git a/drivers/gpu/drm/nouveau/core/subdev/mc/base.c b/drivers/gpu/drm/nouveau/core/subdev/mc/base.c
>>> > index ec9cd6f..02b337e 100644
>>> > --- a/drivers/gpu/drm/nouveau/core/subdev/mc/base.c
>>> > +++ b/drivers/gpu/drm/nouveau/core/subdev/mc/base.c
>>> > @@ -23,6 +23,7 @@
>>> >   */
>>> >
>>> >  #include <subdev/mc.h>
>>> > +#include <core/option.h>
>>> >
>>> >  static irqreturn_t
>>> >  nouveau_mc_intr(int irq, void *arg)
>>> > @@ -43,6 +44,9 @@ nouveau_mc_intr(int irq, void *arg)
>>> >                 map++;
>>> >         }
>>> >
>>> > +       if (pmc->use_msi)
>>> > +               nv_wr08(pmc->base.base.parent, 0x00088068, 0xff);
>>> Register not present everywhere.
>>>
>>> At the very least, the enabling of MSI should be disallowed on the
>>> earlier chipsets where it's not supported.  Though, it's perhaps
>>> possible that the pci_enable_msi() call will fail in all of these
>>> cases anyway.. I'm not certain.
>>>
>> MSIs are required property for everything doing PCIe. So the only cases
>> where this should fail is plain PCI/AGP devices. I don't really have a
>> test system for those old cards set up.
>>
>> But I remember Ilia having some legacy things plugged in, so maybe he
>> could test this patch and see how it goes?
>
> Sure, let me know what you need -- I have nv18 PCI, nv34 PCIe (note
> that it's not native PCIe, but some sort of bridge thing IIRC),
Cases like the nv34 here (i think there's some nv4x that aren't native
pcie too) are what I'm wondering about primarily.

> nv42
> PCIe, nv44 PCIe, nv96 PCIe.
>
> Can I just apply this patch, or do I need to do the whole series? What
> constitutes a success?
>
>   -ilia