/** * intel_update_watermarks - update FIFO watermark values based on current modes * * Calculate watermark values for the various WM regs based on current mode * and plane configuration. * * There are several cases to deal with here: * - normal (i.e. non-self-refresh) * - self-refresh (SR) mode * - lines are large relative to FIFO size (buffer can hold up to 2) * - lines are small relative to FIFO size (buffer can hold more than 2 * lines), so need to account for TLB latency * * The normal calculation is: * watermark = dotclock * bytes per pixel * latency * where latency is platform & configuration dependent (we assume pessimal * values here). * * The SR calculation is: * watermark = (trunc(latency/line time)+1) * surface width * * bytes per pixel * where * line time = htotal / dotclock * surface width = hdisplay for normal plane and 64 for cursor * and latency is assumed to be high, as above. * * The final value programmed to the register should always be rounded up, * and include an extra 2 entries to account for clock crossings. * * We don't use the sprite, so we can ignore that. And on Crestline we have * to set the non-SR watermarks to 8. */