i965/hsw: Enable L3 atomics.
Improves performance of the arb_shader_image_load_store-atomicity piglit test by over 25x (which isn't a real benchmark it's just heavy on atomics -- the improvement in a microbenchmark I wrote a while ago seemed to be even greater). The drawback is one needs to be extra-careful not to hang the GPU (in fact the whole system). A DC partition must have been allocated on L3, the "convert L3 cycle for DC to UC" bit may not be set, the MOCS L3 cacheability bit must be set for all surfaces accessed using DC atomics, and the SCRATCH1 and ROW_CHICKEN3 bits must be kept in sync. A fairly recent kernel is required for the command parser to allow writes to these registers. Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com> Acked-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
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@ -258,5 +258,19 @@ setup_l3_config(struct brw_context *brw, const struct brw_l3_config *cfg)
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SET_FIELD(cfg->n[L3P_T], GEN7_L3CNTLREG3_T_ALLOC));
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ADVANCE_BATCH();
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if (brw->is_haswell && brw->intelScreen->cmd_parser_version >= 4) {
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/* Enable L3 atomics on HSW if we have a DC partition, otherwise keep
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* them disabled to avoid crashing the system hard.
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*/
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BEGIN_BATCH(5);
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OUT_BATCH(MI_LOAD_REGISTER_IMM | (5 - 2));
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OUT_BATCH(HSW_SCRATCH1);
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OUT_BATCH(has_dc ? 0 : HSW_SCRATCH1_L3_ATOMIC_DISABLE);
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OUT_BATCH(HSW_ROW_CHICKEN3);
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OUT_BATCH(HSW_ROW_CHICKEN3_L3_ATOMIC_DISABLE << 16 |
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(has_dc ? 0 : HSW_ROW_CHICKEN3_L3_ATOMIC_DISABLE));
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ADVANCE_BATCH();
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}
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}
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}
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