Hi Robin,
Thanks for your feedback!
On Tue, Feb 12, 2019 at 06:46:40PM +0000, Robin Murphy wrote:
> On 11/02/2019 15:02, Maxime Ripard wrote:
> > Now that we can express our DMA topology, rely on those property instead of
> > hardcoding an offset from the dma_addr_t which wasn't really great.
> >
> > We still need to add some code to deal with the old DT that would lack that
> > property, but we move the offset to the DRM device dma_pfn_offset to be
> > able to rely on just the dma_addr_t associated to the GEM object.
> >
> > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/sun4i/sun4i_backend.c | 28 +++++++++++++++++++++-------
> > 1 file changed, 21 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
> > index 9e9255ee59cd..1846a1b30fea 100644
> > --- a/drivers/gpu/drm/sun4i/sun4i_backend.c
> > +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
> > @@ -383,13 +383,6 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
> > paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
> > DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);
> > - /*
> > - * backend DMA accesses DRAM directly, bypassing the system
> > - * bus. As such, the address range is different and the buffer
> > - * address needs to be corrected.
> > - */
> > - paddr -= PHYS_OFFSET;
> > -
> > if (fb->format->is_yuv)
> > return sun4i_backend_update_yuv_buffer(backend, fb, paddr);
> > @@ -835,6 +828,27 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
> > dev_set_drvdata(dev, backend);
> > spin_lock_init(&backend->frontend_lock);
> > + if (of_find_property(dev->of_node, "interconnects", NULL)) {
> > + /*
> > + * This assume we have the same DMA constraints for all our the
> > + * devices in our pipeline (all the backends, but also the
> > + * frontends). This sounds bad, but it has always been the case
> > + * for us, and DRM doesn't do per-device allocation either, so
> > + * we would need to fix DRM first...
> > + */
> > + ret = of_dma_configure(drm->dev, dev->of_node, true);
>
> It would be even nicer if we could ensure that drm->dev originates from a DT
> node which has the appropriate interconnects property itself, such that we
> can assume it's already configured correctly.
The thing is drm->dev comes from a node in the DT that is a virtual
node, and therefore doesn't have any resources attached, so I'm not
sure we have any other way, unfortunately.
Maxime
--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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