diff options
| author | Jesse Barnes | 2009-08-31 10:24:31 -0700 |
|---|---|---|
| committer | Eric Anholt | 2009-09-02 10:33:01 -0700 |
| commit | bcc24fb42585dc9f490cf7789a917358414bdab5 (patch) | |
| tree | b9d48fecfd6ed4f5a0ba3b6c4837670612974d92 | |
| parent | 37d0892c5a94e208cf863e3b7bac014edee4346d (diff) | |
drm/i915: increase default latency constant (v2 w/comment)
Some i915/i945 platforms have a fairly high memory latency in certain
situations, so increase our constant a bit to avoid FIFO underruns.
The effect should be positive on other platforms as well; we'll have a
bit more insurance against a busy memory subsystem due to the extra
FIFO entries.
Fixes fdo bug #23368. Needed for 2.6.31.
Tested-by: Sven Arvidsson <sa@whiz.se>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
| -rw-r--r-- | drivers/gpu/drm/i915/intel_display.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 3fadb5358858..748ed50c55ca 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -2005,7 +2005,21 @@ static void igd_enable_cxsr(struct drm_device *dev, unsigned long clock, return; } -const static int latency_ns = 3000; /* default for non-igd platforms */ +/* + * Latency for FIFO fetches is dependent on several factors: + * - memory configuration (speed, channels) + * - chipset + * - current MCH state + * It can be fairly high in some situations, so here we assume a fairly + * pessimal value. It's a tradeoff between extra memory fetches (if we + * set this value too high, the FIFO will fetch frequently to stay full) + * and power consumption (set it too low to save power and we might see + * FIFO underruns and display "flicker"). + * + * A value of 5us seems to be a good balance; safe for very low end + * platforms but not overly aggressive on lower latency configs. + */ +const static int latency_ns = 5000; static int intel_get_fifo_size(struct drm_device *dev, int plane) { |