On Friday 12 May 2017 05:53 AM, Matt Roper wrote:
On Mon, May 08, 2017 at 05:18:58PM +0530, Mahesh Kumar wrote:
DDB minimum requirement may exceed the allocated DDB for CRTC/Pipe. This
patch make changes to fail the flip if minimum requirement for pipe
exceeds the total ddb allocated to the pipe.
Previously it succeeded but making alloc_size a negative value. Which
will make later calculations for plane ddb allocation bogus & may lead
to screen corruption or system hang.
I think originally the bspec defined the initial minimum DDB allocation
for each plane to just be '8' in all cases. So even with 4 planes on a
pipe, your initial pipe minimum would only be 32, so the code here never
had a risk of overflowing (note that the initial minimum is different
than the WM0 minimum requirement we ultimately wind up calculating).
But then the bspec was updated to suggest a higher initial minimum for
y-tiled buffers (calculated based on the width of the buffer), so our
initial assumptions here don't really hold anymore. We should still be
safe if we're not using y-tile, but even a single 4k y-tiled plane would
have an initial minimum of something like 250 blocks iirc., so we can't
assume we're always safe anymore.
Signed-off-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2a4e9d89cd6f..0ace94d67432 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3591,6 +3591,7 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
int num_active;
unsigned plane_data_rate[I915_MAX_PLANES] = {};
unsigned plane_y_data_rate[I915_MAX_PLANES] = {};
+ uint16_t total_min_blocks = 0;
/* Clear the partitioning for disabled planes. */
memset(ddb->plane[pipe], 0, sizeof(ddb->plane[pipe]));
@@ -3618,10 +3619,18 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
*/
for_each_plane_id_on_crtc(intel_crtc, plane_id) {
- alloc_size -= minimum[plane_id];
- alloc_size -= y_minimum[plane_id];
+ total_min_blocks += minimum[plane_id];
+ total_min_blocks += y_minimum[plane_id];
}
+ if ((total_min_blocks > alloc_size)) {
+ DRM_DEBUG_KMS("Requested display configuration exceeds system DDB limitations");
+ DRM_DEBUG_KMS("minimum required %d/%d\n", total_min_blocks,
+ alloc_size);
+ return-EINVAL;
I think you're missing a space here?
With that fixed,
I think I already fixed this in newer version of patch. :),
anyway resubmitting complete series again with other comments addressed.
thanks,
-Mahesh
Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
+ }
+
+ alloc_size -= total_min_blocks;
ddb->plane[pipe][PLANE_CURSOR].start = alloc->end - minimum[PLANE_CURSOR];
ddb->plane[pipe][PLANE_CURSOR].end = alloc->end;
--
2.11.0
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