On gen4+, we program the CRTC offset into the DSPTILEOFF register, which is limited to 12-bits of integer precision in both the x and the y axes. Programming a value larger than or equal to 4096 results in a wraparound of the CRTC location and a distorted output. This is undesirable, so abort the operation and report the error condition.
We could attempt to mitigate this error by recomputing the DSPSURF base address to a nearby tile-row and adjusting the offsets relative to the fake CRTC subsurface. However, the question is whether this is common enough to merit a workaround as only clients that use a single composite fb and not per-crtc-fb such as X suffer. Such a design (rendering directly into a single composite fb across the scanouts) interacts badly with the power management of the display engine and is strongly discouraged; future windowing systems are designed around being able to page-flip per-crtc-fb. Within X itself, the mechanisms are already in place to avoid making such setcrtc requests, at a slight cost to efficiency. Cc: [email protected] Signed-off-by: Chris Wilson <[email protected]> --- drivers/gpu/drm/i915/intel_display.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 5708d9b..bd3f84b 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -1995,6 +1995,11 @@ static int i9xx_update_plane(struct drm_crtc *crtc, struct drm_framebuffer *fb, return -EINVAL; } + if (INTEL_INFO(dev)->gen >= 4 && (x|y) & ~4095) { + DRM_ERROR("CRTC offset too larget (%d, %d)\n", x, y); + return -EINVAL; + } + intel_fb = to_intel_framebuffer(fb); obj = intel_fb->obj; @@ -2069,6 +2074,11 @@ static int ironlake_update_plane(struct drm_crtc *crtc, return -EINVAL; } + if ((x|y) & ~4095) { + DRM_ERROR("CRTC offset too larget (%d, %d)\n", x, y); + return -EINVAL; + } + intel_fb = to_intel_framebuffer(fb); obj = intel_fb->obj; -- 1.7.10 _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
