On Mon, 2019-01-28 at 14:29 +0100, Thomas Hellström wrote:
> Hi,
>
> On Mon, 2019-01-28 at 12:21 +0000, Koenig, Christian wrote:
> > Am 25.01.19 um 14:05 schrieb Thomas Hellstrom:
> > > The vmwgfx driver needs to know whether the dma page pool is
> > > enabled
> > > to determine whether to refuse loading if the dma mode logic
> > > requests coherent memory from the dma page pool.
> > >
> > > Cc: "Koenig, Christian" <Christian.Koenig@xxxxxxx>
> > > Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 11 +++++++++++
> > > include/drm/ttm/ttm_page_alloc.h | 4 ++++
> > > 2 files changed, 15 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> > > b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> > > index d594f7520b7b..adf8cc189ecc 100644
> > > --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> > > +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> > > @@ -1235,4 +1235,15 @@ int ttm_dma_page_alloc_debugfs(struct
> > > seq_file *m, void *data)
> > > }
> > > EXPORT_SYMBOL_GPL(ttm_dma_page_alloc_debugfs);
> > >
> > > +/**
> > > + * ttm_dma_page_alloc_enabled - Is the dma page pool enabled?
> > > + *
> > > + * Returns true if the dma page pool is enabled. false
> > > otherwise.
> > > + */
> > > +bool ttm_dma_page_alloc_enabled(void)
> > > +{
> > > + return !!_manager;
> > > +}
> > > +EXPORT_SYMBOL(ttm_dma_page_alloc_enabled);
> > > +
> >
> > This is completely superfluous cause the manager is enabled as soon
> > as
> > it is compiled in.
> >
> > You could just use "#if defined(CONFIG_SWIOTLB) ||
> > defined(CONFIG_INTEL_IOMMU)" instead.
> >
> > Christian.
> >
>
> Yes, that's what was done before in vmgwfx, but it's very fragile and
> based on assumptions about what various parts of TTM does and doesn't
> do. Chances are somebody would modify the enablement and forget to
> modify this function.
>
> But of course I can change it if you think that'd be better.
>
> /Thomas
>
What about
static inline bool ttm_dma_page_alloc_enabled(void)
{
return (IS_ENABLED(CONFIG_INTEL_IOMMU) ||
IS_ENABLED(CONFIG_SWIOTLB)) && _manager;
}
to avoid that layering violation?
/Thomas
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