[PATCH 2/2] drm/i915: Add DSC support to MST path
Govindapillai, Vinod
vinod.govindapillai at intel.com
Thu Aug 25 16:04:33 UTC 2022
On Thu, 2022-08-25 at 18:17 +0300, Lisovskiy, Stanislav wrote:
> On Thu, Aug 25, 2022 at 05:58:19PM +0300, Govindapillai, Vinod wrote:
> > Hi Stan,
> >
> > Some comments inline..
> >
> > On Mon, 2022-08-22 at 12:40 +0300, Stanislav Lisovskiy wrote:
> > > Whenever we are not able to get enough timeslots
> > > for required PBN, let's try to allocate those
> > > using DSC, just same way as we do for SST.
> > >
> > > v2: Removed intel_dp_mst_dsc_compute_config and refactored
> > > intel_dp_dsc_compute_config to support timeslots as a
> > > parameter(Ville Syrjälä)
> > >
> > > v3: - Rebased
> > > - Added a debug to see that we at least try reserving
> > > VCPI slots using DSC, because currently its not visible
> > > from the logs, thus making debugging more tricky.
> > > - Moved timeslots to numerator, where it should be.
> > >
> > > v4: - Call drm_dp_mst_atomic_check already during link
> > > config computation, because we need to know already
> > > by this moment if uncompressed amount of VCPI slots
> > > needed can fit, otherwise we need to use DSC.
> > > (thanks to Vinod Govindapillai for pointing this out)
> > >
> > > v5: - Put pipe_config->bigjoiner_pipes back to original
> > > condition in intel_dp_dsc_compute_config
> > > (don't remember when I lost it)
> > >
> > > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> > > ---
> > > drivers/gpu/drm/i915/display/intel_dp.c | 73 ++++-----
> > > drivers/gpu/drm/i915/display/intel_dp.h | 17 +++
> > > drivers/gpu/drm/i915/display/intel_dp_mst.c | 157 ++++++++++++++++++++
> > > 3 files changed, 205 insertions(+), 42 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > > index 32292c0be2bd..519b436fc530 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > > @@ -116,7 +116,6 @@ bool intel_dp_is_edp(struct intel_dp *intel_dp)
> > > }
> > >
> > > static void intel_dp_unset_edid(struct intel_dp *intel_dp);
> > > -static int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc);
> > >
> > > /* Is link rate UHBR and thus 128b/132b? */
> > > bool intel_dp_is_uhbr(const struct intel_crtc_state *crtc_state)
> > > @@ -687,11 +686,12 @@ small_joiner_ram_size_bits(struct drm_i915_private *i915)
> > > return 6144 * 8;
> > > }
> > >
> > > -static u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> > > - u32 link_clock, u32 lane_count,
> > > - u32 mode_clock, u32 mode_hdisplay,
> > > - bool bigjoiner,
> > > - u32 pipe_bpp)
> > > +u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> > > + u32 link_clock, u32 lane_count,
> > > + u32 mode_clock, u32 mode_hdisplay,
> > > + bool bigjoiner,
> > > + u32 pipe_bpp,
> > > + u32 timeslots)
> > > {
> > > u32 bits_per_pixel, max_bpp_small_joiner_ram;
> > > int i;
> > > @@ -702,8 +702,9 @@ static u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> > > * for SST -> TimeSlotsPerMTP is 1,
> > > * for MST -> TimeSlotsPerMTP has to be calculated
> > > */
> > > - bits_per_pixel = (link_clock * lane_count * 8) /
> > > + bits_per_pixel = (link_clock * lane_count * 8) * timeslots /
> > > intel_dp_mode_to_fec_clock(mode_clock);
> > > + drm_dbg_kms(&i915->drm, "Max link bpp: %u\n", bits_per_pixel);
> > >
> > > /* Small Joiner Check: output bpp <= joiner RAM (bits) / Horiz. width */
> > > max_bpp_small_joiner_ram = small_joiner_ram_size_bits(i915) /
> > > @@ -752,9 +753,9 @@ static u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> > > return bits_per_pixel << 4;
> > > }
> > >
> > > -static u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
> > > - int mode_clock, int mode_hdisplay,
> > > - bool bigjoiner)
> > > +u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
> > > + int mode_clock, int mode_hdisplay,
> > > + bool bigjoiner)
> > > {
> > > struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > u8 min_slice_count, i;
> > > @@ -961,8 +962,8 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
> > > return MODE_OK;
> > > }
> > >
> > > -static bool intel_dp_need_bigjoiner(struct intel_dp *intel_dp,
> > > - int hdisplay, int clock)
> > > +bool intel_dp_need_bigjoiner(struct intel_dp *intel_dp,
> > > + int hdisplay, int clock)
> > > {
> > > struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > >
> > > @@ -1049,7 +1050,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
> > > target_clock,
> > > mode->hdisplay,
> > > bigjoiner,
> > > - pipe_bpp) >> 4;
> > > + pipe_bpp, 1) >> 4;
> > > dsc_slice_count =
> > > intel_dp_dsc_get_slice_count(intel_dp,
> > > target_clock,
> > > @@ -1354,7 +1355,7 @@ intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
> > > return -EINVAL;
> > > }
> > >
> > > -static int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 max_req_bpc)
> > > +int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 max_req_bpc)
> > > {
> > > struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > int i, num_bpc;
> > > @@ -1444,10 +1445,11 @@ static int intel_dp_dsc_compute_params(struct intel_encoder *encoder,
> > > return drm_dsc_compute_rc_parameters(vdsc_cfg);
> > > }
> > >
> > > -static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > - struct intel_crtc_state *pipe_config,
> > > - struct drm_connector_state *conn_state,
> > > - struct link_config_limits *limits)
> > > +int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > + struct intel_crtc_state *pipe_config,
> > > + struct drm_connector_state *conn_state,
> > > + struct link_config_limits *limits,
> > > + int timeslots)
> > > {
> > > struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> > > struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
> > > @@ -1498,7 +1500,8 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > adjusted_mode->crtc_clock,
> > > adjusted_mode->crtc_hdisplay,
> > > pipe_config->bigjoiner_pipes,
> > > - pipe_bpp);
> > > + pipe_bpp,
> > > + timeslots);
> > > dsc_dp_slice_count =
> > > intel_dp_dsc_get_slice_count(intel_dp,
> > > adjusted_mode->crtc_clock,
> > > @@ -1510,27 +1513,13 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > return -EINVAL;
> > > }
> > > pipe_config->dsc.compressed_bpp = min_t(u16,
> > > - dsc_max_output_bpp >> 4,
> > > - pipe_config->pipe_bpp);
> > > + dsc_max_output_bpp >> 4,
> > > + pipe_config->pipe_bpp);
> > > pipe_config->dsc.slice_count = dsc_dp_slice_count;
> > > + drm_dbg_kms(&dev_priv->drm, "DSC: compressed bpp %d slice count %d\n",
> > > + pipe_config->dsc.compressed_bpp,
> > > + pipe_config->dsc.slice_count);
> > > }
> > > -
> > > - /* As of today we support DSC for only RGB */
> > > - if (intel_dp->force_dsc_bpp) {
> > > - if (intel_dp->force_dsc_bpp >= 8 &&
> > > - intel_dp->force_dsc_bpp < pipe_bpp) {
> > > - drm_dbg_kms(&dev_priv->drm,
> > > - "DSC BPP forced to %d",
> > > - intel_dp->force_dsc_bpp);
> > > - pipe_config->dsc.compressed_bpp =
> > > - intel_dp->force_dsc_bpp;
> > > - } else {
> > > - drm_dbg_kms(&dev_priv->drm,
> > > - "Invalid DSC BPP %d",
> > > - intel_dp->force_dsc_bpp);
> > > - }
> > > - }
> > > -
> > > /*
> > > * VDSC engine operates at 1 Pixel per clock, so if peak pixel rate
> > > * is greater than the maximum Cdclock and if slice count is even
> > > @@ -1538,13 +1527,13 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > */
> > > if (adjusted_mode->crtc_clock > dev_priv->max_cdclk_freq ||
> > > pipe_config->bigjoiner_pipes) {
> > > - if (pipe_config->dsc.slice_count < 2) {
> > > + if (pipe_config->dsc.slice_count > 1) {
> > > + pipe_config->dsc.dsc_split = true;
> > > + } else {
> > > drm_dbg_kms(&dev_priv->drm,
> > > "Cannot split stream to use 2 VDSC instances\n");
> > > return -EINVAL;
> > > }
> > > -
> > > - pipe_config->dsc.dsc_split = true;
> > > }
> > >
> > > ret = intel_dp_dsc_compute_params(&dig_port->base, pipe_config);
> > > @@ -1633,7 +1622,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
> > > str_yes_no(ret), str_yes_no(joiner_needs_dsc),
> > > str_yes_no(intel_dp->force_dsc_en));
> > > ret = intel_dp_dsc_compute_config(intel_dp, pipe_config,
> > > - conn_state, &limits);
> > > + conn_state, &limits, 1);
> > > if (ret < 0)
> > > return ret;
> > > }
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> > > index a54902c713a3..c6539a6915e9 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> > > @@ -56,6 +56,11 @@ void intel_dp_encoder_flush_work(struct drm_encoder *encoder);
> > > int intel_dp_compute_config(struct intel_encoder *encoder,
> > > struct intel_crtc_state *pipe_config,
> > > struct drm_connector_state *conn_state);
> > > +int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > > + struct intel_crtc_state *pipe_config,
> > > + struct drm_connector_state *conn_state,
> > > + struct link_config_limits *limits,
> > > + int timeslots);
> > > bool intel_dp_is_edp(struct intel_dp *intel_dp);
> > > bool intel_dp_is_uhbr(const struct intel_crtc_state *crtc_state);
> > > bool intel_dp_is_port_edp(struct drm_i915_private *dev_priv, enum port port);
> > > @@ -96,6 +101,18 @@ void intel_read_dp_sdp(struct intel_encoder *encoder,
> > > struct intel_crtc_state *crtc_state,
> > > unsigned int type);
> > > bool intel_digital_port_connected(struct intel_encoder *encoder);
> > > +int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc);
> > > +u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> > > + u32 link_clock, u32 lane_count,
> > > + u32 mode_clock, u32 mode_hdisplay,
> > > + bool bigjoiner,
> > > + u32 pipe_bpp,
> > > + u32 timeslots);
> > > +u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
> > > + int mode_clock, int mode_hdisplay,
> > > + bool bigjoiner);
> > > +bool intel_dp_need_bigjoiner(struct intel_dp *intel_dp,
> > > + int hdisplay, int clock);
> > >
> > > static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
> > > {
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > index 14d2a64193b2..b4d68c324e68 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > @@ -99,6 +99,84 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
> > > return 0;
> > > }
> > >
> > > +static int intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
> > > + struct intel_crtc_state *crtc_state,
> > > + struct drm_connector_state *conn_state,
> > > + struct link_config_limits *limits)
> > > +{
> > > + struct drm_atomic_state *state = crtc_state->uapi.state;
> > > + struct intel_dp_mst_encoder *intel_mst = enc_to_mst(encoder);
> > > + struct intel_dp *intel_dp = &intel_mst->primary->dp;
> > > + struct intel_connector *connector =
> > > + to_intel_connector(conn_state->connector);
> > > + struct drm_i915_private *i915 = to_i915(connector->base.dev);
> > > + const struct drm_display_mode *adjusted_mode =
> > > + &crtc_state->hw.adjusted_mode;
> > > + bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
> > > + DP_DPCD_QUIRK_CONSTANT_N);
> > > + int bpp, slots = -EINVAL;
> > > + int i, num_bpc;
> > > + u8 dsc_bpc[3] = {0};
> > > + int min_bpp, max_bpp;
> > > + u8 dsc_max_bpc;
> > > +
> > > + crtc_state->lane_count = limits->max_lane_count;
> > > + crtc_state->port_clock = limits->max_rate;
> > > +
> > > + /* Max DSC Input BPC for ICL is 10 and for TGL+ is 12 */
> > > + if (DISPLAY_VER(i915) >= 12)
> > > + dsc_max_bpc = min_t(u8, 12, conn_state->max_requested_bpc);
> > > + else
> > > + dsc_max_bpc = min_t(u8, 10, conn_state->max_requested_bpc);
> > > +
> > > + max_bpp = min_t(u8, dsc_max_bpc * 3, limits->max_bpp);
> > > + min_bpp = limits->min_bpp;
> > > +
> > > + num_bpc = drm_dp_dsc_sink_supported_input_bpcs(intel_dp->dsc_dpcd,
> > > + dsc_bpc);
> > > + for (i = 0; i < num_bpc; i++) {
> > > + if (max_bpp >= dsc_bpc[i] * 3)
> > > + if (min_bpp > dsc_bpc[i] * 3)
> > > + min_bpp = dsc_bpc[i] * 3;
> > > + }
> > > +
> > > + drm_dbg_kms(&i915->drm, "DSC Sink supported min bpp %d max bpp %d\n",
> > > + min_bpp, max_bpp);
> > > +
> > > + for (bpp = max_bpp; bpp >= min_bpp; bpp -= 2 * 3) {
> > > + crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock,
> > > + bpp << 4,
> > > + true);
> > > +
> > > + slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
> > > + connector->port,
> > > + crtc_state->pbn, 0);
> > > +
> > > + drm_dbg_kms(&i915->drm, "Trying bpp %d got %d pbn %d slots\n",
> > > + bpp, crtc_state->pbn, slots);
> > > +
> > > + if (slots == -EDEADLK)
> > > + return slots;
> > > + if (slots >= 0)
> > > + break;
> > Based on our understanding that drm_dp_atomic_find_vcpi_slots" doesn't check any limits, we
> > cannot
> > use that as a basis for "slots" decision, isnt it? Don't you need to use the same
> > drm_dp_mst_atomic_check() here as well?
> >
> > Or move the drm_dp_mst_atomic_check() to the intel_dp_mst_compute_link_config()?
>
> That would be double check because we do call that check later in intel_atomic_check
> anyway. I had to add it here, just to decide if we use DSC or not. However if here we
> chose DSC and drm_dp_atomic_find_vcpi_slots returns amount of VCPI slots that can't be
> fit - drm_dp_mst_atomic_check which is called later in intel_atomic_check will take care
> of that. Just like it would take care if DSC was not supported and we ran out of BW/MST slots..
>
> Stan
Okay. I got that part. if you are keeping the logic like that, then there is no need to do loop over
max_bpp to min_bpp here. Because bpp = max_bpp will never fail, the DSC will be always attempted
with the max_bpp. And as you mentioned eventually intel_atomic_check() will catch if it is too big.
But if the intention is to find the right "bpp" which might still fit to the link, we should iterate
over the bpp-s like you have here. But in that case the decision has to be based on one more
"drm_dp_mst_atomic_check()"
BR
Vinod
>
> >
> > > + }
> > > +
> > > + if (slots < 0) {
> > > + drm_dbg_kms(&i915->drm, "failed finding vcpi slots:%d\n",
> > > + slots);
> > > + return slots;
> > > + }
> > > +
> > > + intel_link_compute_m_n(crtc_state->pipe_bpp,
> > > + crtc_state->lane_count,
> > > + adjusted_mode->crtc_clock,
> > > + crtc_state->port_clock,
> > > + &crtc_state->dp_m_n,
> > > + constant_n, crtc_state->fec_enable);
> > > + crtc_state->dp_m_n.tu = slots;
> > > +
> > > + return 0;
> > > +}
> > > static int intel_dp_mst_update_slots(struct intel_encoder *encoder,
> > > struct intel_crtc_state *crtc_state,
> > > struct drm_connector_state *conn_state)
> > > @@ -127,6 +205,7 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
> > > struct drm_connector_state *conn_state)
> > > {
> > > struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > > + struct drm_atomic_state *state = pipe_config->uapi.state;
> > > struct intel_dp_mst_encoder *intel_mst = enc_to_mst(encoder);
> > > struct intel_dp *intel_dp = &intel_mst->primary->dp;
> > > struct intel_connector *connector =
> > > @@ -175,6 +254,38 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
> > >
> > > ret = intel_dp_mst_compute_link_config(encoder, pipe_config,
> > > conn_state, &limits);
> > > +
> > > + if (ret == -EDEADLK)
> > > + return ret;
> > > +
> > > + /*
> > > + * We need to check if VCPI slots allocated can actually fit already
> > > + * here, to decide whether we use DSC or not.
> > > + * If either intel_dp_mst_compute_link_config or that one fails,
> > > + * then we try DSC as last resort.
> > > + */
> > > + if (!ret)
> > > + ret = drm_dp_mst_atomic_check(state);
> > > +
> > > + /* enable compression if the mode doesn't fit available BW */
> > > + drm_dbg_kms(&dev_priv->drm, "Force DSC en = %d\n", intel_dp->force_dsc_en);
> > > + if (ret || intel_dp->force_dsc_en) {
> > > + /*
> > > + * Try to get at least some timeslots and then see, if
> > > + * we can fit there with DSC.
> > > + */
> > > + drm_dbg_kms(&dev_priv->drm, "Trying to find VCPI slots in DSC mode\n");
> > > +
> > > + ret = intel_dp_dsc_mst_compute_link_config(encoder, pipe_config,
> > > + conn_state, &limits);
> > > + if (ret < 0)
> > > + return ret;
> > > +
> > > + ret = intel_dp_dsc_compute_config(intel_dp, pipe_config,
> > > + conn_state, &limits,
> > > + pipe_config->dp_m_n.tu);
> > > + }
> > > +
> > > if (ret)
> > > return ret;
> > >
> > > @@ -713,6 +824,10 @@ intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
> > > int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
> > > int max_rate, mode_rate, max_lanes, max_link_clock;
> > > int ret;
> > > + bool dsc = false, bigjoiner = false;
> > > + u16 dsc_max_output_bpp = 0;
> > > + u8 dsc_slice_count = 0;
> > > + int target_clock = mode->clock;
> > >
> > > if (drm_connector_is_unregistered(connector)) {
> > > *status = MODE_ERROR;
> > > @@ -750,6 +865,48 @@ intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
> > > return 0;
> > > }
> > >
> > > + if (intel_dp_need_bigjoiner(intel_dp, mode->hdisplay, target_clock)) {
> > > + bigjoiner = true;
> > > + max_dotclk *= 2;
> > > + }
> > > +
> > > + if (DISPLAY_VER(dev_priv) >= 10 &&
> > > + drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd)) {
> > > + /*
> > > + * TBD pass the connector BPC,
> > > + * for now U8_MAX so that max BPC on that platform would be picked
> > > + */
> > > + int pipe_bpp = intel_dp_dsc_compute_bpp(intel_dp, U8_MAX);
> > > +
> > > + if (drm_dp_sink_supports_fec(intel_dp->fec_capable)) {
> > > + dsc_max_output_bpp =
> > > + intel_dp_dsc_get_output_bpp(dev_priv,
> > > + max_link_clock,
> > > + max_lanes,
> > > + target_clock,
> > > + mode->hdisplay,
> > > + bigjoiner,
> > > + pipe_bpp, 1) >> 4;
> > > + dsc_slice_count =
> > > + intel_dp_dsc_get_slice_count(intel_dp,
> > > + target_clock,
> > > + mode->hdisplay,
> > > + bigjoiner);
> > > + }
> > > +
> > > + dsc = dsc_max_output_bpp && dsc_slice_count;
> > > + }
> > > +
> > > + /*
> > > + * Big joiner configuration needs DSC for TGL which is not true for
> > > + * XE_LPD where uncompressed joiner is supported.
> > > + */
> > > + if (DISPLAY_VER(dev_priv) < 13 && bigjoiner && !dsc)
> > > + return MODE_CLOCK_HIGH;
> > > +
> > > + if (mode_rate > max_rate && !dsc)
> > > + return MODE_CLOCK_HIGH;
> > > +
> > > *status = intel_mode_valid_max_plane_size(dev_priv, mode, false);
> > > return 0;
> > > }
> >
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