23.03.2021 18:54, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
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@nvidia.com
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.*/
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(?).