Quoting Lionel Landwerlin (2019-07-09 10:32:02)
> +static u32 *save_register(struct drm_i915_private *i915, u32 *cs,
> + i915_reg_t reg, u32 offset, u32 dword_count)
> +{
> + uint32_t d;
> +
> + for (d = 0; d < dword_count; d++) {
> + *cs++ = INTEL_GEN(i915) >= 8 ?
> + MI_STORE_REGISTER_MEM_GEN8 : MI_STORE_REGISTER_MEM;
> + *cs++ = i915_mmio_reg_offset(reg) + 4 * d;
> + *cs++ = intel_gt_scratch_offset(&i915->gt, offset) + 4 * d;
> + if (INTEL_GEN(i915) >= 8)
> + *cs++ = 0;
restore_register doesn't care about the extra MI_NOOP :)
> + }
> +
> + return cs;
> +}
> +
> +static u32 *restore_register(struct drm_i915_private *i915, u32 *cs,
> + i915_reg_t reg, u32 offset, u32 dword_count)
> +{
> + uint32_t d;
> +
> + for (d = 0; d < dword_count; d++) {
> + *cs++ = INTEL_GEN(i915) >= 8 ?
> + MI_LOAD_REGISTER_MEM_GEN8 : MI_LOAD_REGISTER_MEM;
> + *cs++ = i915_mmio_reg_offset(reg);
> + *cs++ = intel_gt_scratch_offset(&i915->gt, offset);
> + *cs++ = 0;
> + }
> +
> + return cs;
> +}
> +
> +static int alloc_noa_wait(struct drm_i915_private *i915)
> +{
> + struct drm_i915_gem_object *bo;
> + struct i915_vma *vma;
> + u64 delay_ns = atomic64_read(&i915->perf.oa.noa_programming_delay), delay_ticks;
I would const u64 delay_ticks = foo(i915);
That would save the distraction later in the middle of CS.
> + u32 *batch, *ts0, *cs, *jump;
> + int ret, i;
> + enum { START_TS, NOW_TS, DELTA_TS, JUMP_PREDICATE, DELTA_TARGET, N_CS_GPR };
> +
> + bo = i915_gem_object_create_internal(i915, 4096);
> + if (IS_ERR(bo)) {
> + DRM_ERROR("Failed to allocate NOA wait batchbuffer\n");
> + return PTR_ERR(bo);
> + }
> +
> + /*
> + * We pin in GGTT because we jump into this buffer now because
> + * multiple OA config BOs will have a jump to this address and it
> + * needs to be fixed during the lifetime of the i915/perf stream.
> + */
> + vma = i915_gem_object_ggtt_pin(bo, NULL, 0, 4096, 0);
> + if (IS_ERR(vma)) {
> + ret = PTR_ERR(vma);
> + goto err_unref;
> + }
> +
> + batch = cs = i915_gem_object_pin_map(bo, I915_MAP_WB);
> + if (IS_ERR(batch)) {
> + ret = PTR_ERR(batch);
> + goto err_unpin;
> + }
> +
> + /* Save registers. */
> + for (i = 0; i < N_CS_GPR; i++) {
> + cs = save_register(i915, cs, HSW_CS_GPR(i),
> + INTEL_GT_SCRATCH_FIELD_PERF_CS_GPR + 8 * i, 2);
> + }
> + cs = save_register(i915, cs, MI_PREDICATE_RESULT_1,
> + INTEL_GT_SCRATCH_FIELD_PERF_PREDICATE_RESULT_1, 1);
> +
> + /* First timestamp snapshot location. */
> + ts0 = cs;
> +
> + /*
> + * Initial snapshot of the timestamp register to implement the wait.
> + * We work with 32b values, so clear out the top 32b bits of the
> + * register because the ALU works 64bits.
> + */
> + *cs++ = MI_LOAD_REGISTER_IMM(1);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(START_TS)) + 4;
> + *cs++ = 0;
> + *cs++ = MI_LOAD_REGISTER_REG | (3 - 2);
> + *cs++ = i915_mmio_reg_offset(RING_TIMESTAMP(RENDER_RING_BASE));
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(START_TS));
> +
> + /*
> + * This is the location we're going to jump back into until the
> + * required amount of time has passed.
> + */
> + jump = cs;
> +
> + /*
> + * Take another snapshot of the timestamp register. Take care to clear
> + * up the top 32bits of CS_GPR(1) as we're using it for other
> + * operations below.
> + */
> + *cs++ = MI_LOAD_REGISTER_IMM(1);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(NOW_TS)) + 4;
> + *cs++ = 0;
> + *cs++ = MI_LOAD_REGISTER_REG | (3 - 2);
> + *cs++ = i915_mmio_reg_offset(RING_TIMESTAMP(RENDER_RING_BASE));
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(NOW_TS));
> +
> + /*
> + * Do a diff between the 2 timestamps and store the result back into
> + * CS_GPR(1).
> + */
> + *cs++ = MI_MATH(5);
> + *cs++ = MI_ALU_OP(MI_ALU_OP_LOAD, MI_ALU_SRC_SRCA, MI_ALU_SRC_REG(NOW_TS));
> + *cs++ = MI_ALU_OP(MI_ALU_OP_LOAD, MI_ALU_SRC_SRCB, MI_ALU_SRC_REG(START_TS));
> + *cs++ = MI_ALU_OP(MI_ALU_OP_SUB, 0, 0);
> + *cs++ = MI_ALU_OP(MI_ALU_OP_STORE, MI_ALU_SRC_REG(DELTA_TS), MI_ALU_SRC_ACCU);
> + *cs++ = MI_ALU_OP(MI_ALU_OP_STORE, MI_ALU_SRC_REG(JUMP_PREDICATE), MI_ALU_SRC_CF);
> +
> + /*
> + * Transfer the carry flag (set to 1 if ts1 < ts0, meaning the
> + * timestamp have rolled over the 32bits) into the predicate register
> + * to be used for the predicated jump.
> + */
> + *cs++ = MI_LOAD_REGISTER_REG | (3 - 2);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(JUMP_PREDICATE));
> + *cs++ = i915_mmio_reg_offset(MI_PREDICATE_RESULT_1);
> +
> + /* Restart from the beginning if we had timestamps roll over. */
> + *cs++ = (INTEL_GEN(i915) < 8 ?
> + MI_BATCH_BUFFER_START : MI_BATCH_BUFFER_START_GEN8) |
> + MI_BATCH_PREDICATE;
> + *cs++ = i915_ggtt_offset(vma) + (ts0 - batch) * 4;
> + *cs++ = 0;
> +
> + /*
> + * Now add the diff between to previous timestamps and add it to :
> + * (((1 * << 64) - 1) - delay_ns)
> + *
> + * When the Carry Flag contains 1 this means the elapsed time is
> + * longer than the expected delay, and we can exit the wait loop.
> + */
> + delay_ticks = 0xffffffffffffffff -
> + DIV64_U64_ROUND_UP(delay_ns *
> + RUNTIME_INFO(i915)->cs_timestamp_frequency_khz,
> + 1000000ull);
> + *cs++ = MI_LOAD_REGISTER_IMM(2);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(DELTA_TARGET));
> + *cs++ = lower_32_bits(delay_ticks);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(DELTA_TARGET)) + 4;
> + *cs++ = upper_32_bits(delay_ticks);
> +
> + *cs++ = MI_MATH(4);
> + *cs++ = MI_ALU_OP(MI_ALU_OP_LOAD, MI_ALU_SRC_SRCA, MI_ALU_SRC_REG(DELTA_TS));
> + *cs++ = MI_ALU_OP(MI_ALU_OP_LOAD, MI_ALU_SRC_SRCB, MI_ALU_SRC_REG(DELTA_TARGET));
> + *cs++ = MI_ALU_OP(MI_ALU_OP_ADD, 0, 0);
> + *cs++ = MI_ALU_OP(MI_ALU_OP_STOREINV, MI_ALU_SRC_REG(JUMP_PREDICATE), MI_ALU_SRC_CF);
> +
> + /*
> + * Transfer the result into the predicate register to be used for the
> + * predicated jump.
> + */
> + *cs++ = MI_LOAD_REGISTER_REG | (3 - 2);
> + *cs++ = i915_mmio_reg_offset(HSW_CS_GPR(JUMP_PREDICATE));
> + *cs++ = i915_mmio_reg_offset(MI_PREDICATE_RESULT_1);
> +
> + /* Predicate the jump. */
> + *cs++ = (INTEL_GEN(i915) < 8 ?
> + MI_BATCH_BUFFER_START : MI_BATCH_BUFFER_START_GEN8) |
> + MI_BATCH_PREDICATE;
> + *cs++ = i915_ggtt_offset(vma) + (jump - batch) * 4;
> + *cs++ = 0;
> +
> + /* Restore registers. */
> + for (i = 0; i < N_CS_GPR; i++) {
> + cs = restore_register(i915, cs, HSW_CS_GPR(i),
> + INTEL_GT_SCRATCH_FIELD_PERF_CS_GPR + 8 * i, 2);
> + }
> + cs = restore_register(i915, cs, MI_PREDICATE_RESULT_1,
> + INTEL_GT_SCRATCH_FIELD_PERF_PREDICATE_RESULT_1, 1);
> +
> + /* And return to the ring. */
> + *cs++ = MI_BATCH_BUFFER_END;
> +
> + GEM_BUG_ON((cs - batch) > (PAGE_SIZE / sizeof(*batch)));
> +
> + i915_gem_object_flush_map(bo);
> + i915_gem_object_unpin_map(bo);
> +
> + i915->perf.oa.noa_wait = vma;
> +
> + return 0;
> +
> +err_unpin:
> + __i915_vma_unpin(vma);
> +
> +err_unref:
> + i915_gem_object_put(bo);
> +
> + return ret;
> +}
Preferably with the nit above,
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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