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

[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.

> +
>         if (intr) {
>                 nv_error(pmc, "unknown intr 0x%08x\n", stat);
>         }
> @@ -75,6 +79,8 @@ _nouveau_mc_dtor(struct nouveau_object *object)
>         struct nouveau_device *device = nv_device(object);
>         struct nouveau_mc *pmc = (void *)object;
>         free_irq(device->pdev->irq, pmc);
> +       if (pmc->use_msi)
> +               pci_disable_msi(device->pdev);
>         nouveau_subdev_destroy(&pmc->base);
>  }
>
> @@ -96,6 +102,17 @@ nouveau_mc_create_(struct nouveau_object *parent, struct nouveau_object *engine,
>
>         pmc->intr_map = intr_map;
>
> +       pmc->use_msi = nouveau_boolopt(device->cfgopt, "NvMSI", true);
> +       if (pmc->use_msi) {
> +               ret = pci_enable_msi(device->pdev);
> +               if (ret) {
> +                       pmc->use_msi = false;
> +               } else {
> +                       nv_wr08(device, 0x00088068, 0xff);
> +                       nv_info(pmc, "MSI interrupts enabled\n");
> +               }
> +       }
> +
>         ret = request_irq(device->pdev->irq, nouveau_mc_intr,
>                           IRQF_SHARED, "nouveau", pmc);
>         if (ret < 0)
> --
> 1.8.3.1
>