On Thu, Dec 06, 2018 at 03:55:41PM -0800, Matt Roper wrote:
> The DDB allocation algorithm currently used by the driver grants each
> plane a very small minimum allocation of DDB blocks and then divies up
> all of the remaining blocks based on the percentage of the total data
> rate that the plane makes up. It turns out that this proportional
> allocation approach is overly-generous with the larger planes and can
> leave very small planes wthout a big enough allocation to even hit their
> level 0 watermark requirements (especially on APL, which has a smaller
> DDB in general than other gen9 platforms). Or there can be situations
> where the smallest planes hit a lower watermark level than they should
> have been able to hit with a more equitable division of DDB blocks, thus
> limiting the overall system sleep state that can be achieved.
>
> The bspec now describes an alternate algorithm that can be used to
> overcome these types of issues. With the new algorithm, we calculate
> all plane watermark values for all wm levels first, then go back and
> partition a pipe's DDB space second. The DDB allocation will calculate
> what the highest watermark level that can be achieved on *all* active
> planes, and then grant the blocks necessary to hit that level to each
> plane. Any remaining blocks are then divided up proportionally
> according to data rate, similar to the old algorithm.
OK, so it's somewhat similar to what I already did for VLV/CHV. The
difference being that on VLV/CHV I distribute purely based on the
level 0 watermark and don't even consider the data rates. Not sure
if there's a significant difference between the two approaches.
>
> There was a previous attempt to implement this algorithm a couple years
> ago in bb9d85f6e9d ("drm/i915/skl: New ddb allocation algorithm"), but
> some regressions were reported, the patch was reverted, and nobody
> ever got around to figuring out exactly where the bug was in that
> version. Our watermark code has evolved significantly in the meantime,
> but we're still getting bug reports caused by the unfair proportional
> algorithm, so let's give this another shot.
>
> v2:
> - Make sure cursor allocation stays constant and fixed at the end of
> the pipe allocation.
> - Fix some watermark level iterators that weren't handling the max
> level.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105458
> Signed-off-by: Matt Roper <matthew.d.ro...@intel.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 350
> +++++++++++++++-------------------------
> 1 file changed, 129 insertions(+), 221 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index b09c2a257ff1..6db2bf7b037c 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4306,102 +4306,6 @@ icl_get_total_relative_data_rate(struct
> intel_crtc_state *intel_cstate,
> return total_data_rate;
> }
>
> -static uint16_t
> -skl_ddb_min_alloc(const struct drm_plane_state *pstate, const int plane)
> -{
> - struct drm_framebuffer *fb = pstate->fb;
> - struct intel_plane_state *intel_pstate = to_intel_plane_state(pstate);
> - uint32_t src_w, src_h;
> - uint32_t min_scanlines = 8;
> - uint8_t plane_bpp;
> -
> - if (WARN_ON(!fb))
> - return 0;
> -
> - /* For packed formats, and uv-plane, return 0 */
> - if (plane == 1 && fb->format->format != DRM_FORMAT_NV12)
> - return 0;
> -
> - /* For Non Y-tile return 8-blocks */
> - if (fb->modifier != I915_FORMAT_MOD_Y_TILED &&
> - fb->modifier != I915_FORMAT_MOD_Yf_TILED &&
> - fb->modifier != I915_FORMAT_MOD_Y_TILED_CCS &&
> - fb->modifier != I915_FORMAT_MOD_Yf_TILED_CCS)
> - return 8;
> -
> - /*
> - * Src coordinates are already rotated by 270 degrees for
> - * the 90/270 degree plane rotation cases (to match the
> - * GTT mapping), hence no need to account for rotation here.
> - */
> - src_w = drm_rect_width(&intel_pstate->base.src) >> 16;
> - src_h = drm_rect_height(&intel_pstate->base.src) >> 16;
> -
> - /* Halve UV plane width and height for NV12 */
> - if (plane == 1) {
> - src_w /= 2;
> - src_h /= 2;
> - }
> -
> - plane_bpp = fb->format->cpp[plane];
> -
> - if (drm_rotation_90_or_270(pstate->rotation)) {
> - switch (plane_bpp) {
> - case 1:
> - min_scanlines = 32;
> - break;
> - case 2:
> - min_scanlines = 16;
> - break;
> - case 4:
> - min_scanlines = 8;
> - break;
> - case 8:
> - min_scanlines = 4;
> - break;
> - default:
> - WARN(1, "Unsupported pixel depth %u for rotation",
> - plane_bpp);
> - min_scanlines = 32;
> - }
> - }
> -
> - return DIV_ROUND_UP((4 * src_w * plane_bpp), 512) * min_scanlines/4 + 3;
> -}
> -
> -static void
> -skl_ddb_calc_min(const struct intel_crtc_state *cstate, int num_active,
> - uint16_t *minimum, uint16_t *uv_minimum)
> -{
> - const struct drm_plane_state *pstate;
> - struct drm_plane *plane;
> -
> - drm_atomic_crtc_state_for_each_plane_state(plane, pstate,
> &cstate->base) {
> - enum plane_id plane_id = to_intel_plane(plane)->id;
> - struct intel_plane_state *plane_state =
> to_intel_plane_state(pstate);
> -
> - if (plane_id == PLANE_CURSOR)
> - continue;
> -
> - /* slave plane must be invisible and calculated from master */
> - if (!pstate->visible || WARN_ON(plane_state->slave))
> - continue;
> -
> - if (!plane_state->linked_plane) {
> - minimum[plane_id] = skl_ddb_min_alloc(pstate, 0);
> - uv_minimum[plane_id] = skl_ddb_min_alloc(pstate, 1);
> - } else {
> - enum plane_id y_plane_id =
> - plane_state->linked_plane->id;
> -
> - minimum[y_plane_id] = skl_ddb_min_alloc(pstate, 0);
> - minimum[plane_id] = skl_ddb_min_alloc(pstate, 1);
> - }
> - }
> -
> - minimum[PLANE_CURSOR] = skl_cursor_allocation(num_active);
> -}
> -
> static int
> skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
> struct skl_ddb_allocation *ddb /* out */)
> @@ -4411,15 +4315,18 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
> struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> struct skl_ddb_entry *alloc = &cstate->wm.skl.ddb;
> - uint16_t alloc_size, start;
> - uint16_t minimum[I915_MAX_PLANES] = {};
> - uint16_t uv_minimum[I915_MAX_PLANES] = {};
> + struct skl_ddb_entry *plane_alloc, *uv_plane_alloc;
> + struct skl_plane_wm *wm;
This one at least could be moved into a tighter scope AFAICS.
> + uint16_t alloc_size, start = 0;
> + uint16_t total[I915_MAX_PLANES] = {};
> + uint16_t uv_total[I915_MAX_PLANES] = {};
> u64 total_data_rate;
> enum plane_id plane_id;
> int num_active;
> u64 plane_data_rate[I915_MAX_PLANES] = {};
> u64 uv_plane_data_rate[I915_MAX_PLANES] = {};
> - uint16_t total_min_blocks = 0;
> + uint16_t blocks = 0;
> + int level;
>
> /* Clear the partitioning for disabled planes. */
> memset(cstate->wm.skl.plane_ddb_y, 0,
> sizeof(cstate->wm.skl.plane_ddb_y));
> @@ -4449,81 +4356,112 @@ skl_allocate_pipe_ddb(struct intel_crtc_state
> *cstate,
> if (alloc_size == 0)
> return 0;
>
> - skl_ddb_calc_min(cstate, num_active, minimum, uv_minimum);
> + /* Allocate fixed number of blocks for cursor. */
> + total[PLANE_CURSOR] = skl_cursor_allocation(num_active);
> + alloc_size -= total[PLANE_CURSOR];
> + cstate->wm.skl.plane_ddb_y[PLANE_CURSOR].start =
> + alloc->end - total[PLANE_CURSOR];
> + cstate->wm.skl.plane_ddb_y[PLANE_CURSOR].end = alloc->end;
> +
> + if (total_data_rate == 0)
> + return 0;
>
> /*
> - * 1. Allocate the mininum required blocks for each active plane
> - * and allocate the cursor, it doesn't require extra allocation
> - * proportional to the data rate.
> + * Find the highest watermark level for which we can satisfy the block
> + * requirement of active planes.
> */
> + for (level = ilk_wm_max_level(dev_priv); level >= 0; level--) {
> + for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> + if (plane_id == PLANE_CURSOR)
> + continue;
>
> - for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> - total_min_blocks += minimum[plane_id];
> - total_min_blocks += uv_minimum[plane_id];
> + wm = &cstate->wm.skl.optimal.planes[plane_id];
> + blocks += wm->wm[level].plane_res_b;
> + blocks += wm->uv_wm[level].plane_res_b;
> + }
> +
> + if (blocks < alloc_size) {
> + alloc_size -= blocks;
> + break;
> + }
> }
>
> - if (total_min_blocks > alloc_size) {
> + if (level < 0) {
> DRM_DEBUG_KMS("Requested display configuration exceeds system
> DDB limitations");
> - DRM_DEBUG_KMS("minimum required %d/%d\n", total_min_blocks,
> - alloc_size);
> + DRM_DEBUG_KMS("minimum required %d/%d\n", blocks,
> + alloc_size);
> return -EINVAL;
> }
>
> - alloc_size -= total_min_blocks;
> - cstate->wm.skl.plane_ddb_y[PLANE_CURSOR].start = alloc->end -
> minimum[PLANE_CURSOR];
> - cstate->wm.skl.plane_ddb_y[PLANE_CURSOR].end = alloc->end;
> -
> /*
> - * 2. Distribute the remaining space in proportion to the amount of
> - * data each plane needs to fetch from memory.
> - *
> - * FIXME: we may not allocate every single block here.
> + * Grant each plane the blocks it requires at the highest achievable
> + * watermark level, plus an extra share of the leftover blocks
> + * proportional to its relative data rate.
> */
> - if (total_data_rate == 0)
> - return 0;
> -
> - start = alloc->start;
> for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> - u64 data_rate, uv_data_rate;
> - uint16_t plane_blocks, uv_plane_blocks;
> + u64 rate;
>
> if (plane_id == PLANE_CURSOR)
> continue;
>
> - data_rate = plane_data_rate[plane_id];
> + wm = &cstate->wm.skl.optimal.planes[plane_id];
>
> - /*
> - * allocation for (packed formats) or (uv-plane part of planar
> format):
> - * promote the expression to 64 bits to avoid overflowing, the
> - * result is < available as data_rate / total_data_rate < 1
> - */
> - plane_blocks = minimum[plane_id];
> - plane_blocks += div64_u64(alloc_size * data_rate,
> total_data_rate);
> + rate = plane_data_rate[plane_id];
> + total[plane_id] = wm->wm[level].plane_res_b +
> + div64_u64(alloc_size * rate, total_data_rate);
This might still leave some blocks unused no? On VLV/CHV I used
DIV_ROUND_UP()+min()+WARN() to make sure we never a block behind.
>
> - /* Leave disabled planes at (0,0) */
> - if (data_rate) {
> - cstate->wm.skl.plane_ddb_y[plane_id].start = start;
> - cstate->wm.skl.plane_ddb_y[plane_id].end = start +
> plane_blocks;
> - }
> -
> - start += plane_blocks;
> + rate = uv_plane_data_rate[plane_id];
> + uv_total[plane_id] = wm->uv_wm[level].plane_res_b +
> + div64_u64(alloc_size * rate, total_data_rate);
> + }
>
> - /* Allocate DDB for UV plane for planar format/NV12 */
> - uv_data_rate = uv_plane_data_rate[plane_id];
> + /* Set the actual DDB start/end points for each plane */
> + start = alloc->start;
> + for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> + if (plane_id == PLANE_CURSOR)
> + continue;
>
> - uv_plane_blocks = uv_minimum[plane_id];
> - uv_plane_blocks += div64_u64(alloc_size * uv_data_rate,
> total_data_rate);
> + plane_alloc = &cstate->wm.skl.plane_ddb_y[plane_id];
> + uv_plane_alloc = &cstate->wm.skl.plane_ddb_uv[plane_id];
>
> /* Gen11+ uses a separate plane for UV watermarks */
> - WARN_ON(INTEL_GEN(dev_priv) >= 11 && uv_plane_blocks);
> + WARN_ON(INTEL_GEN(dev_priv) >= 11 && uv_total[plane_id]);
>
> - if (uv_data_rate) {
> - cstate->wm.skl.plane_ddb_uv[plane_id].start = start;
> - cstate->wm.skl.plane_ddb_uv[plane_id].end =
> - start + uv_plane_blocks;
> + /* Leave disabled planes at (0,0) */
> + if (total[plane_id]) {
> + plane_alloc->start = start;
> + plane_alloc->end = start += total[plane_id];
> + }
> +
> + if (uv_total[plane_id]) {
> + uv_plane_alloc->start = start;
> + uv_plane_alloc->end = start + uv_total[plane_id];
> + }
> + }
> +
> + /*
> + * When we calculated watermark values we didn't know how high
> + * of a level we'd actually be able to hit, so we just marked
> + * all levels as "enabled." Go back now and disable the ones
> + * that aren't actually possible.
> + */
> + while (level++ <= ilk_wm_max_level(dev_priv)) {
I'd prefer a for-loop.
> + for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> + wm = &cstate->wm.skl.optimal.planes[plane_id];
> + wm->wm[level].plane_en = false;
> + wm->wm[level].plane_res_b = 0;
> + wm->wm[level].plane_res_l = 0;
> }
> + }
>
> - start += uv_plane_blocks;
> + /*
> + * Go back and disable the transition watermark if it turns out we
> + * don't have enough DDB blocks for it.
> + */
> + for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> + wm = &cstate->wm.skl.optimal.planes[plane_id];
> + if (wm->trans_wm.plane_res_b > total[plane_id])
> + wm->trans_wm.plane_en = false;
Since we use memcmp() to check for dirty watermarks we should
probably zero out plane_res_b/l here too. Maybe even use memset()
for clearing each disabled trans/normal wm.
> }
>
> return 0;
> @@ -4720,17 +4658,15 @@ skl_compute_plane_wm_params(const struct
> intel_crtc_state *cstate,
> return 0;
> }
>
> -static int skl_compute_plane_wm(const struct intel_crtc_state *cstate,
> - const struct intel_plane_state *intel_pstate,
> - uint16_t ddb_allocation,
> - int level,
> - const struct skl_wm_params *wp,
> - const struct skl_wm_level *result_prev,
> - struct skl_wm_level *result /* out */)
> +static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
> + const struct intel_plane_state *intel_pstate,
> + int level,
> + const struct skl_wm_params *wp,
> + const struct skl_wm_level *result_prev,
> + struct skl_wm_level *result /* out */)
> {
> struct drm_i915_private *dev_priv =
> to_i915(intel_pstate->base.plane->dev);
> - const struct drm_plane_state *pstate = &intel_pstate->base;
> uint32_t latency = dev_priv->wm.skl_latency[level];
> uint_fixed_16_16_t method1, method2;
> uint_fixed_16_16_t selected_result;
> @@ -4740,9 +4676,6 @@ static int skl_compute_plane_wm(const struct
> intel_crtc_state *cstate,
> bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
> uint32_t min_disp_buf_needed;
>
> - if (latency == 0)
> - return level == 0 ? -EINVAL : 0;
> -
> /* Display WA #1141: kbl,cfl */
> if ((IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv) ||
> IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_B0)) &&
> @@ -4828,38 +4761,24 @@ static int skl_compute_plane_wm(const struct
> intel_crtc_state *cstate,
> min_disp_buf_needed = res_blocks;
> }
>
> - if ((level > 0 && res_lines > 31) ||
> - res_blocks >= ddb_allocation ||
> - min_disp_buf_needed >= ddb_allocation) {
Since you're removing this thing the calculation of min_disp_buf_needed
is now pointless AFAICS.
> - /*
> - * If there are no valid level 0 watermarks, then we can't
> - * support this display configuration.
> - */
> - if (level) {
> - return 0;
> - } else {
> - struct drm_plane *plane = pstate->plane;
> -
> - DRM_DEBUG_KMS("Requested display configuration exceeds
> system watermark limitations\n");
> - DRM_DEBUG_KMS("[PLANE:%d:%s] blocks required = %u/%u,
> lines required = %u/31\n",
> - plane->base.id, plane->name,
> - res_blocks, ddb_allocation, res_lines);
> - return -EINVAL;
> - }
> - }
> -
> /* The number of lines are ignored for the level 0 watermark. */
> + if (level > 0 && res_lines > 31)
> + return;
> +
> + /*
> + * If res_lines is valid, assume we can use this watermark level
> + * for now. We'll come back and disable it after we calculate the
> + * DDB allocation if it turns out we don't actually have enough
> + * blocks to satisfy it.
> + */
> result->plane_res_b = res_blocks;
> result->plane_res_l = res_lines;
> result->plane_en = true;
> -
> - return 0;
> }
>
> -static int
> +static void
> skl_compute_wm_levels(const struct intel_crtc_state *cstate,
> const struct intel_plane_state *intel_pstate,
> - uint16_t ddb_blocks,
> const struct skl_wm_params *wm_params,
> struct skl_wm_level *levels)
> {
> @@ -4867,25 +4786,15 @@ skl_compute_wm_levels(const struct intel_crtc_state
> *cstate,
> to_i915(intel_pstate->base.plane->dev);
> int level, max_level = ilk_wm_max_level(dev_priv);
> struct skl_wm_level *result_prev = &levels[0];
> - int ret;
>
> for (level = 0; level <= max_level; level++) {
> struct skl_wm_level *result = &levels[level];
>
> - ret = skl_compute_plane_wm(cstate,
> - intel_pstate,
> - ddb_blocks,
> - level,
> - wm_params,
> - result_prev,
> - result);
> - if (ret)
> - return ret;
> + skl_compute_plane_wm(cstate, intel_pstate, level, wm_params,
> + result_prev, result);
>
> result_prev = result;
> }
> -
> - return 0;
> }
>
> static uint32_t
> @@ -4913,8 +4822,7 @@ skl_compute_linetime_wm(const struct intel_crtc_state
> *cstate)
>
> static void skl_compute_transition_wm(const struct intel_crtc_state *cstate,
> const struct skl_wm_params *wp,
> - struct skl_plane_wm *wm,
> - uint16_t ddb_allocation)
> + struct skl_plane_wm *wm)
> {
> struct drm_device *dev = cstate->base.crtc->dev;
> const struct drm_i915_private *dev_priv = to_i915(dev);
> @@ -4962,34 +4870,38 @@ static void skl_compute_transition_wm(const struct
> intel_crtc_state *cstate,
>
> }
>
> - res_blocks += 1;
> -
> - if (res_blocks < ddb_allocation) {
> - wm->trans_wm.plane_res_b = res_blocks;
> - wm->trans_wm.plane_en = true;
> - }
> + /*
> + * Just assume we can enable the transition watermark. After
> + * computing the DDB we'll come back and disable it if that
> + * assumption turns out to be false.
> + */
> + wm->trans_wm.plane_res_b = res_blocks + 1;
> + wm->trans_wm.plane_en = true;
> }
>
> static int skl_build_plane_wm_single(struct intel_crtc_state *crtc_state,
> const struct intel_plane_state
> *plane_state,
> enum plane_id plane_id, int color_plane)
> {
> + struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
> struct skl_plane_wm *wm = &crtc_state->wm.skl.optimal.planes[plane_id];
> - u16 ddb_blocks =
> skl_ddb_entry_size(&crtc_state->wm.skl.plane_ddb_y[plane_id]);
> struct skl_wm_params wm_params;
> int ret;
>
> + /*
> + * This can only happen if someone overrides the latency to an invalid
> + * value of 0 in debugfs.
> + */
> + if (dev_priv->wm.skl_latency[0] == 0)
> + return -EINVAL;
I guess we don't actually need this anymore. I think it should end
up automagically handled by the ddb allocation failing on account
of skl_wm_method{1,2}() returning "some big number".
> +
> ret = skl_compute_plane_wm_params(crtc_state, plane_state,
> &wm_params, color_plane);
> if (ret)
> return ret;
>
> - ret = skl_compute_wm_levels(crtc_state, plane_state,
> - ddb_blocks, &wm_params, wm->wm);
> - if (ret)
> - return ret;
> -
> - skl_compute_transition_wm(crtc_state, &wm_params, wm, ddb_blocks);
> + skl_compute_wm_levels(crtc_state, plane_state, &wm_params, wm->wm);
> + skl_compute_transition_wm(crtc_state, &wm_params, wm);
>
> return 0;
> }
> @@ -4999,7 +4911,6 @@ static int skl_build_plane_wm_uv(struct
> intel_crtc_state *crtc_state,
> enum plane_id plane_id)
> {
> struct skl_plane_wm *wm = &crtc_state->wm.skl.optimal.planes[plane_id];
> - u16 ddb_blocks =
> skl_ddb_entry_size(&crtc_state->wm.skl.plane_ddb_uv[plane_id]);
> struct skl_wm_params wm_params;
> int ret;
>
> @@ -5011,10 +4922,7 @@ static int skl_build_plane_wm_uv(struct
> intel_crtc_state *crtc_state,
> if (ret)
> return ret;
>
> - ret = skl_compute_wm_levels(crtc_state, plane_state,
> - ddb_blocks, &wm_params, wm->uv_wm);
> - if (ret)
> - return ret;
> + skl_compute_wm_levels(crtc_state, plane_state, &wm_params, wm->uv_wm);
>
> return 0;
> }
> @@ -5532,13 +5440,9 @@ skl_compute_wm(struct drm_atomic_state *state)
> if (ret || !changed)
> return ret;
>
> - ret = skl_compute_ddb(state);
> - if (ret)
> - return ret;
> -
> /*
> * Calculate WM's for all pipes that are part of this transaction.
> - * Note that the DDB allocation above may have added more CRTC's that
> + * Note that skl_ddb_add_affected_pipes may have added more CRTC's that
> * weren't otherwise being modified (and set bits in dirty_pipes) if
> * pipe allocations had to change.
> */
> @@ -5568,6 +5472,10 @@ skl_compute_wm(struct drm_atomic_state *state)
> intel_cstate->update_wm_pre = true;
> }
>
> + ret = skl_compute_ddb(state);
> + if (ret)
> + return ret;
> +
> skl_print_wm_changes(intel_state);
>
> return 0;
> --
> 2.14.4
>
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> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel
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