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drm/i915: Include TLB miss overhead for computing WM 

The docs recommend that if 8 display lines fit inside the FIFO buffer,
then the number of watermark entries should be increased to hide the
latency of filling the rest of the FIFO buffer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2011-01-08 09:02:21 +00:00
parent 882417851a
commit db66e37d23
1 changed files with 9 additions and 2 deletions
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11
drivers/gpu/drm/i915/intel_display.c
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@ -3425,8 +3425,9 @@ static bool ironlake_compute_wm0(struct drm_device *dev,
int *cursor_wm) int *cursor_wm)
{ {
struct drm_crtc *crtc; struct drm_crtc *crtc;
int htotal, hdisplay, clock, pixel_size = 0; int htotal, hdisplay, clock, pixel_size;
int line_time_us, line_count, entries; int line_time_us, line_count;
int entries, tlb_miss;
crtc = intel_get_crtc_for_pipe(dev, pipe); crtc = intel_get_crtc_for_pipe(dev, pipe);
if (crtc->fb == NULL || !crtc->enabled) if (crtc->fb == NULL || !crtc->enabled)
@ -3439,6 +3440,9 @@ static bool ironlake_compute_wm0(struct drm_device *dev,
/* Use the small buffer method to calculate plane watermark */ /* Use the small buffer method to calculate plane watermark */
entries = ((clock * pixel_size / 1000) * display_latency_ns) / 1000; entries = ((clock * pixel_size / 1000) * display_latency_ns) / 1000;
tlb_miss = display->fifo_size*display->cacheline_size - hdisplay * 8;
if (tlb_miss > 0)
entries += tlb_miss;
entries = DIV_ROUND_UP(entries, display->cacheline_size); entries = DIV_ROUND_UP(entries, display->cacheline_size);
*plane_wm = entries + display->guard_size; *plane_wm = entries + display->guard_size;
if (*plane_wm > (int)display->max_wm) if (*plane_wm > (int)display->max_wm)
@ -3448,6 +3452,9 @@ static bool ironlake_compute_wm0(struct drm_device *dev,
line_time_us = ((htotal * 1000) / clock); line_time_us = ((htotal * 1000) / clock);
line_count = (cursor_latency_ns / line_time_us + 1000) / 1000; line_count = (cursor_latency_ns / line_time_us + 1000) / 1000;
entries = line_count * 64 * pixel_size; entries = line_count * 64 * pixel_size;
tlb_miss = cursor->fifo_size*cursor->cacheline_size - hdisplay * 8;
if (tlb_miss > 0)
entries += tlb_miss;
entries = DIV_ROUND_UP(entries, cursor->cacheline_size); entries = DIV_ROUND_UP(entries, cursor->cacheline_size);
*cursor_wm = entries + cursor->guard_size; *cursor_wm = entries + cursor->guard_size;
if (*cursor_wm > (int)cursor->max_wm) if (*cursor_wm > (int)cursor->max_wm)