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| author | Jesse Barnes <jbarnes@virtuousgeek.org> | 2009-09-11 12:25:56 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-10-05 09:32:06 -0700 |
| commit | a0cea65ea326b6a87487349e04d1b6dd513b9c3b (patch) | |
| tree | 388e10010943e1056d61b1f4a423821ec7ef7d65 /drivers | |
| parent | 29732ca5d6284c507cefd0b2b76b05b96b3a4f7d (diff) | |
| download | lwn-a0cea65ea326b6a87487349e04d1b6dd513b9c3b.tar.gz lwn-a0cea65ea326b6a87487349e04d1b6dd513b9c3b.zip | |
drm/i915: prevent FIFO calculation overflows on 32 bits with high dotclocks
commit d660467c3ff2a0b7413e1b7a51452b34ffb49e5f upstream.
A very high dotclock (e.g. 229500kHz as reported by Anton) can cause
the entries_required variable to overflow, potentially leading to a
FIFO watermark value that's too low to support the given mode. Split
the division across the calculation to avoid this.
Reported-by: Anton Khirnov <wyskas@gmail.com>
Tested-by: Anton Khirnov <wyskas@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_display.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 748ed50c55ca..ff3160ff6e8d 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -1858,7 +1858,14 @@ static unsigned long intel_calculate_wm(unsigned long clock_in_khz, { long entries_required, wm_size; - entries_required = (clock_in_khz * pixel_size * latency_ns) / 1000000; + /* + * Note: we need to make sure we don't overflow for various clock & + * latency values. + * clocks go from a few thousand to several hundred thousand. + * latency is usually a few thousand + */ + entries_required = ((clock_in_khz / 1000) * pixel_size * latency_ns) / + 1000; entries_required /= wm->cacheline_size; DRM_DEBUG("FIFO entries required for mode: %d\n", entries_required); |