[Nouveau] [PATCH v3 4/6] instmem/gk20a: use DMA attributes

[Ben Skeggs]

On Tue, Feb 17, 2015 at 5:48 PM, Alexandre Courbot <acourbot at nvidia.com> wrote:
> instmem for GK20A is allocated using dma_alloc_coherent(), which
> provides us with a coherent CPU mapping that we never use because
> instmem objects are accessed through PRAMIN. Switch to
> dma_alloc_attrs() which gives us the option to dismiss that CPU mapping
> and free up some CPU virtual space.
>
> Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
> ---
>  drm/nouveau/nvkm/subdev/instmem/gk20a.c | 24 ++++++++++++++++++++----
>  lib/include/nvif/os.h                   | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 51 insertions(+), 4 deletions(-)
>
> diff --git a/drm/nouveau/nvkm/subdev/instmem/gk20a.c b/drm/nouveau/nvkm/subdev/instmem/gk20a.c
> index 6176f5072496..4c8af6e3677c 100644
> --- a/drm/nouveau/nvkm/subdev/instmem/gk20a.c
> +++ b/drm/nouveau/nvkm/subdev/instmem/gk20a.c
> @@ -24,6 +24,10 @@
>  #include <core/mm.h>
>  #include <core/device.h>
>
> +#ifdef __KERNEL__
> +#include <linux/dma-attrs.h>
> +#endif
> +
>  #include "priv.h"
>
>  struct gk20a_instobj_priv {
> @@ -34,6 +38,7 @@ struct gk20a_instobj_priv {
>         struct nvkm_mem _mem;
>         void *cpuaddr;
>         dma_addr_t handle;
> +       struct dma_attrs attrs;
>         struct nvkm_mm_node r;
>  };
>
> @@ -91,8 +96,8 @@ gk20a_instobj_dtor(struct nvkm_object *object)
>         if (unlikely(!node->handle))
>                 return;
>
> -       dma_free_coherent(dev, node->mem->size << PAGE_SHIFT, node->cpuaddr,
> -                         node->handle);
> +       dma_free_attrs(dev, node->mem->size << PAGE_SHIFT, node->cpuaddr,
> +                      node->handle, &node->attrs);
>
>         nvkm_instobj_destroy(&node->base);
>  }
> @@ -126,8 +131,19 @@ gk20a_instobj_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
>
>         node->mem = &node->_mem;
>
> -       node->cpuaddr = dma_alloc_coherent(dev, npages << PAGE_SHIFT,
> -                                          &node->handle, GFP_KERNEL);
> +       init_dma_attrs(&node->attrs);
> +       /*
> +        * We will access this memory through PRAMIN and thus do not need a
> +        * consistent CPU pointer
> +        */
> +       dma_set_attr(DMA_ATTR_NON_CONSISTENT, &node->attrs);
> +       dma_set_attr(DMA_ATTR_WEAK_ORDERING, &node->attrs);
> +       dma_set_attr(DMA_ATTR_WRITE_COMBINE, &node->attrs);
> +       dma_set_attr(DMA_ATTR_NO_KERNEL_MAPPING, &node->attrs);
I wonder, is it possible to have a per-priv version of this instead of
per-object?  The kernel's function prototypes aren't marked const or
anything, which gives me some doubts, but it's worth checking.

> +
> +       node->cpuaddr = dma_alloc_attrs(dev, npages << PAGE_SHIFT,
> +                                       &node->handle, GFP_KERNEL,
> +                                       &node->attrs);
>         if (!node->cpuaddr) {
>                 nv_error(priv, "cannot allocate DMA memory\n");
>                 return -ENOMEM;
> diff --git a/lib/include/nvif/os.h b/lib/include/nvif/os.h
> index f6391a58fd11..b4d307e3ac44 100644
> --- a/lib/include/nvif/os.h
> +++ b/lib/include/nvif/os.h
> @@ -683,6 +683,37 @@ dma_free_coherent(struct device *dev, size_t sz, void *vaddr, dma_addr_t bus)
>  {
>  }
>
> +enum dma_attr {
> +       DMA_ATTR_WRITE_BARRIER,
> +       DMA_ATTR_WEAK_ORDERING,
> +       DMA_ATTR_WRITE_COMBINE,
> +       DMA_ATTR_NON_CONSISTENT,
> +       DMA_ATTR_NO_KERNEL_MAPPING,
> +       DMA_ATTR_SKIP_CPU_SYNC,
> +       DMA_ATTR_FORCE_CONTIGUOUS,
> +       DMA_ATTR_MAX,
> +};
> +
> +struct dma_attrs {
> +};
> +
> +static inline void init_dma_attrs(struct dma_attrs *attrs) {}
> +static inline void dma_set_attr(enum dma_attr attr, struct dma_attrs *attrs) {}
> +
> +static inline void *
> +dma_alloc_attrs(struct device *dev, size_t sz, dma_addr_t *hdl, gfp_t gfp,
> +               struct dma_attrs *attrs)
> +{
> +       return NULL;
> +}
> +
> +static inline void
> +dma_free_attrs(struct device *dev, size_t sz, void *vaddr, dma_addr_t bus,
> +              struct dma_attrs *attrs)
> +{
> +}
> +
> +
>  /******************************************************************************
>   * PCI
>   *****************************************************************************/
> --
> 2.3.0
>
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