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>
{
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);