+static inline uint32_t
+compute_vpm_size_in_sectors(const struct v3d_device_info *devinfo)
+{
+ assert(devinfo->vpm_size > 0);
+ const uint32_t sector_size = V3D_CHANNELS * sizeof(uint32_t) * 8;
+ return devinfo->vpm_size / sector_size;
+}
+
+/* Computes various parameters affecting VPM memory configuration for programs
+ * involving geometry shaders to ensure the program fits in memory and honors
+ * requirements described in section "VPM usage" of the programming manual.
+ */
+static void
+compute_vpm_config_gs(struct v3d_device_info *devinfo,
+ struct v3d_vs_prog_data *vs,
+ struct v3d_gs_prog_data *gs,
+ struct vpm_config *vpm_cfg_out)
+{
+ const uint32_t A = vs->separate_segments ? 1 : 0;
+ const uint32_t Ad = vs->vpm_input_size;
+ const uint32_t Vd = vs->vpm_output_size;
+
+ const uint32_t vpm_size = compute_vpm_size_in_sectors(devinfo);
+
+ /* Try to fit program into our VPM memory budget by adjusting
+ * configurable parameters iteratively. We do this in two phases:
+ * the first phase tries to fit the program into the total available
+ * VPM memory. If we suceed at that, then the second phase attempts
+ * to fit the program into half of that budget so we can run bin and
+ * render programs in parallel.
+ */
+ struct vpm_config vpm_cfg[2];
+ struct vpm_config *final_vpm_cfg = NULL;
+ uint32_t phase = 0;
+
+ vpm_cfg[phase].As = 1;
+ vpm_cfg[phase].Gs = 1;
+ vpm_cfg[phase].Gd = gs->vpm_output_size;
+ vpm_cfg[phase].gs_width = gs->simd_width;
+
+ /* While there is a requirement that Vc >= [Vn / 16], this is
+ * always the case when tessellation is not present because in that
+ * case Vn can only be 6 at most (when input primitive is triangles
+ * with adjacency).
+ *
+ * We always choose Vc=2. We can't go lower than this due to GFXH-1744,
+ * and Broadcom has not found it worth it to increase it beyond this
+ * in general. Increasing Vc also increases VPM memory pressure which
+ * can turn up being detrimental for performance in some scenarios.
+ */
+ vpm_cfg[phase].Vc = 2;
+
+ /* Gv is a constraint on the hardware to not exceed the
+ * specified number of vertex segments per GS batch. If adding a
+ * new primitive to a GS batch would result in a range of more
+ * than Gv vertex segments being referenced by the batch, then
+ * the hardware will flush the batch and start a new one. This
+ * means that we can choose any value we want, we just need to
+ * be aware that larger values improve GS batch utilization
+ * at the expense of more VPM memory pressure (which can affect
+ * other performance aspects, such as GS dispatch width).
+ * We start with the largest value, and will reduce it if we
+ * find that total memory pressure is too high.
+ */
+ vpm_cfg[phase].Gv = 3;
+ do {
+ /* When GS is present in absence of TES, then we need to satisfy
+ * that Ve >= Gv. We go with the smallest value of Ve to avoid
+ * increasing memory pressure.
+ */
+ vpm_cfg[phase].Ve = vpm_cfg[phase].Gv;
+
+ uint32_t vpm_sectors =
+ A * vpm_cfg[phase].As * Ad +
+ (vpm_cfg[phase].Vc + vpm_cfg[phase].Ve) * Vd +
+ vpm_cfg[phase].Gs * vpm_cfg[phase].Gd;
+
+ /* Ideally we want to use no more than half of the available
+ * memory so we can execute a bin and render program in parallel
+ * without stalls. If we achieved that then we are done.
+ */
+ if (vpm_sectors <= vpm_size / 2) {
+ final_vpm_cfg = &vpm_cfg[phase];
+ break;
+ }
+
+ /* At the very least, we should not allocate more than the
+ * total available VPM memory. If we have a configuration that
+ * succeeds at this we save it and continue to see if we can
+ * meet the half-memory-use criteria too.
+ */
+ if (phase == 0 && vpm_sectors <= vpm_size) {
+ vpm_cfg[1] = vpm_cfg[0];
+ phase = 1;
+ }
+
+ /* Try lowering Gv */
+ if (vpm_cfg[phase].Gv > 0) {
+ vpm_cfg[phase].Gv--;
+ continue;
+ }
+
+ /* Try lowering GS dispatch width */
+ if (vpm_cfg[phase].gs_width > 1) {
+ do {
+ vpm_cfg[phase].gs_width >>= 1;
+ vpm_cfg[phase].Gd =
+ align(vpm_cfg[phase].Gd, 2) / 2;
+ } while (vpm_cfg[phase].gs_width == 2);
+
+ /* Reset Gv to max after dropping dispatch width */
+ vpm_cfg[phase].Gv = 3;
+ continue;
+ }
+
+ /* We ran out of options to reduce memory pressure. If we
+ * are at phase 1 we have at least a valid configuration, so we
+ * we use that.
+ */
+ if (phase == 1)
+ final_vpm_cfg = &vpm_cfg[0];
+ break;
+ } while (true);
+
+ if (!final_vpm_cfg) {
+ /* FIXME: maybe return a boolean to indicate failure and use
+ * that to stop the submission for this draw call.
+ */
+ fprintf(stderr, "Failed to allocate VPM memory.\n");
+ abort();
+ }
+
+ assert(final_vpm_cfg);
+ assert(final_vpm_cfg->Gd <= 16);
+ assert(final_vpm_cfg->Gv < 4);
+ assert(final_vpm_cfg->Ve < 4);
+ assert(final_vpm_cfg->Vc >= 2 && final_vpm_cfg->Vc <= 4);
+ assert(final_vpm_cfg->gs_width == 1 ||
+ final_vpm_cfg->gs_width == 4 ||
+ final_vpm_cfg->gs_width == 8 ||
+ final_vpm_cfg->gs_width == 16);
+
+ *vpm_cfg_out = *final_vpm_cfg;
+}
projects / mesa.git / commitdiff