23.03.2021 18:54, Thierry Reding пишет: > From: Thierry Reding <treding@xxxxxxxxxx> > > Clarify when a fixed IOV address can be used and when a buffer has to > be mapped before the IOVA can be used. > > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> > --- > drivers/gpu/drm/tegra/plane.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/tegra/plane.c b/drivers/gpu/drm/tegra/plane.c > index 19e8847a164b..793da5d675d2 100644 > --- a/drivers/gpu/drm/tegra/plane.c > +++ b/drivers/gpu/drm/tegra/plane.c > @@ -119,6 +119,14 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state) > dma_addr_t phys_addr, *phys; > struct sg_table *sgt; > > + /* > + * If we're not attached to a domain, we already stored the > + * physical address when the buffer was allocated. If we're > + * part of a group that's shared between all display > + * controllers, we've also already mapped the framebuffer > + * through the SMMU. In both cases we can short-circuit the > + * code below and retrieve the stored IOV address. > + */ > if (!domain || dc->client.group) > phys = &phys_addr; > else > This comment is correct, but the logic feels a bit lame because it should be wasteful to re-map DMA on each FB flip. Personally I don't care much about this since older Tegras use pinned buffers by default, but this shouldn't be good for T124+ users. Perhaps dumb buffers should be pinned to display by default and then we should extend the Tegra UAPI to support BO mapping to display client(?).
