On Tue, Oct 24, 2023 at 04:09:07AM +0300, Imre Deak wrote:
> A follow-up MST patch will need to specify the total BW allocation
> overhead, prepare for that here by passing the amount of overhead
> to intel_link_compute_m_n(), keeping the existing behavior.
>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_display.c | 40 +++++++++++++++++---
> drivers/gpu/drm/i915/display/intel_display.h | 4 +-
> drivers/gpu/drm/i915/display/intel_dp.c | 30 ++++++++++++---
> drivers/gpu/drm/i915/display/intel_dp.h | 2 +
> drivers/gpu/drm/i915/display/intel_dp_mst.c | 8 ++--
> drivers/gpu/drm/i915/display/intel_fdi.c | 5 ++-
> 6 files changed, 71 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 28d85e1e858ea..de352d9c43439 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -2396,17 +2396,45 @@ static void compute_m_n(u32 *ret_m, u32 *ret_n,
> intel_reduce_m_n_ratio(ret_m, ret_n);
> }
>
> +static void
> +add_bw_alloc_overhead(int link_clock, int bw_overhead,
> + int pixel_data_rate, int link_data_rate,
> + u32 *data_m, u32 *data_n)
> +{
> + bool is_uhbr = intel_dp_is_uhbr_rate(link_clock);
> + int ch_coding_efficiency =
> + drm_dp_bw_channel_coding_efficiency(is_uhbr);
> +
> + /*
> + * TODO: adjust for actual UHBR channel coding efficiency and BW
> + * overhead.
> + */
> + if (is_uhbr) {
> + *data_m = pixel_data_rate;
> + *data_n = link_data_rate * 8 / 10;
> + return;
> + }
> +
> + *data_m = DIV_ROUND_UP_ULL(mul_u32_u32(pixel_data_rate, bw_overhead),
> + 1000000);
> + *data_n = DIV_ROUND_DOWN_ULL(mul_u32_u32(link_data_rate, ch_coding_efficiency),
> + 1000000);
> +}
> +
> void
> intel_link_compute_m_n(u16 bits_per_pixel, int nlanes,
> int pixel_clock, int link_clock,
> - struct intel_link_m_n *m_n,
> - bool fec_enable)
> + int bw_overhead,
> + struct intel_link_m_n *m_n)
> {
> u32 data_clock = bits_per_pixel * pixel_clock;
> + u32 data_m;
> + u32 data_n;
>
> - if (fec_enable)
> - data_clock = intel_dp_mode_to_fec_clock(data_clock);
> -
> + add_bw_alloc_overhead(link_clock, bw_overhead,
> + data_clock,
> + link_clock * 10 * nlanes,
> + &data_m, &data_n);
> /*
> * Windows/BIOS uses fixed M/N values always. Follow suit.
> *
> @@ -2416,7 +2444,7 @@ intel_link_compute_m_n(u16 bits_per_pixel, int nlanes,
> */
> m_n->tu = 64;
> compute_m_n(&m_n->data_m, &m_n->data_n,
> - data_clock, link_clock * nlanes * 8,
> + data_m, data_n,
> 0x8000000);
>
> compute_m_n(&m_n->link_m, &m_n->link_n,
> diff --git a/drivers/gpu/drm/i915/display/intel_display.h b/drivers/gpu/drm/i915/display/intel_display.h
> index 0e5dffe8f0189..dea3202849e72 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.h
> +++ b/drivers/gpu/drm/i915/display/intel_display.h
> @@ -395,8 +395,8 @@ u8 intel_calc_active_pipes(struct intel_atomic_state *state,
> u8 active_pipes);
> void intel_link_compute_m_n(u16 bpp, int nlanes,
> int pixel_clock, int link_clock,
> - struct intel_link_m_n *m_n,
> - bool fec_enable);
> + int bw_overhead,
> + struct intel_link_m_n *m_n);
> u32 intel_plane_fb_max_stride(struct drm_i915_private *dev_priv,
> u32 pixel_format, u64 modifier);
> enum drm_mode_status
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 0c0f026fb3161..0235de5bb8cd1 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -121,10 +121,15 @@ bool intel_dp_is_edp(struct intel_dp *intel_dp)
>
> static void intel_dp_unset_edid(struct intel_dp *intel_dp);
>
> +bool intel_dp_is_uhbr_rate(int rate)
> +{
> + return rate >= 1000000;
> +}
> +
> /* Is link rate UHBR and thus 128b/132b? */
> bool intel_dp_is_uhbr(const struct intel_crtc_state *crtc_state)
> {
> - return crtc_state->port_clock >= 1000000;
> + return intel_dp_is_uhbr_rate(crtc_state->port_clock);
> }
>
> static void intel_dp_set_default_sink_rates(struct intel_dp *intel_dp)
> @@ -684,6 +689,20 @@ u32 intel_dp_mode_to_fec_clock(u32 mode_clock)
> 1000000U);
> }
>
> +int intel_dp_bw_fec_overhead(bool fec_enabled)
> +{
> + /*
> + * TODO: Calculate the actual overhead for a given mode.
> + * The hard-coded 1/0.972261=2.853% overhead factor
> + * corresponds (for instance) to the 8b/10b DP FEC 2.4% +
> + * 0.453% DSC overhead. This is enough for a 3840 width mode,
> + * which has a DSC overhead of up to ~0.2%, but may not be
> + * enough for a 1024 width mode where this is ~0.8% (on a 4
> + * lane DP link, with 2 DSC slices and 8 bpp color depth).
> + */
> + return fec_enabled ? DP_DSC_FEC_OVERHEAD_FACTOR : 1000000;
> +}
> +
> static int
> small_joiner_ram_size_bits(struct drm_i915_private *i915)
> {
> @@ -2655,8 +2674,9 @@ intel_dp_drrs_compute_config(struct intel_connector *connector,
> pixel_clock /= pipe_config->splitter.link_count;
>
> intel_link_compute_m_n(link_bpp, pipe_config->lane_count, pixel_clock,
> - pipe_config->port_clock, &pipe_config->dp_m2_n2,
> - pipe_config->fec_enable);
> + pipe_config->port_clock,
> + intel_dp_bw_fec_overhead(pipe_config->fec_enable),
> + &pipe_config->dp_m2_n2);
>
> /* FIXME: abstract this better */
> if (pipe_config->splitter.enable)
> @@ -2837,8 +2857,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> pipe_config->lane_count,
> adjusted_mode->crtc_clock,
> pipe_config->port_clock,
> - &pipe_config->dp_m_n,
> - pipe_config->fec_enable);
> + intel_dp_bw_fec_overhead(pipe_config->fec_enable),
> + &pipe_config->dp_m_n);
>
> /* FIXME: abstract this better */
> if (pipe_config->splitter.enable)
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index 0258580a6aadc..2080575fef69a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -77,6 +77,7 @@ void intel_dp_audio_compute_config(struct intel_encoder *encoder,
> struct drm_connector_state *conn_state);
> bool intel_dp_has_hdmi_sink(struct intel_dp *intel_dp);
> bool intel_dp_is_edp(struct intel_dp *intel_dp);
> +bool intel_dp_is_uhbr_rate(int rate);
> 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);
> enum irqreturn intel_dp_hpd_pulse(struct intel_digital_port *dig_port,
> @@ -137,6 +138,7 @@ static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
> }
>
> u32 intel_dp_mode_to_fec_clock(u32 mode_clock);
> +int intel_dp_bw_fec_overhead(bool fec_enabled);
>
> bool intel_dp_supports_fec(struct intel_dp *intel_dp,
> const struct intel_connector *connector,
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 98d775d862ac4..da496f383f163 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -172,8 +172,8 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
> crtc_state->lane_count,
> adjusted_mode->crtc_clock,
> crtc_state->port_clock,
> - &crtc_state->dp_m_n,
> - crtc_state->fec_enable);
> + intel_dp_bw_fec_overhead(crtc_state),
> + &crtc_state->dp_m_n);
> crtc_state->dp_m_n.tu = slots;
>
> return 0;
> @@ -267,8 +267,8 @@ static int intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
> crtc_state->lane_count,
> adjusted_mode->crtc_clock,
> crtc_state->port_clock,
> - &crtc_state->dp_m_n,
> - crtc_state->fec_enable);
> + intel_dp_bw_fec_overhead(crtc_state),
> + &crtc_state->dp_m_n);
> crtc_state->dp_m_n.tu = slots;
>
> return 0;
> diff --git a/drivers/gpu/drm/i915/display/intel_fdi.c b/drivers/gpu/drm/i915/display/intel_fdi.c
> index e6429dfebe159..1d87fbc1e8138 100644
> --- a/drivers/gpu/drm/i915/display/intel_fdi.c
> +++ b/drivers/gpu/drm/i915/display/intel_fdi.c
> @@ -10,6 +10,7 @@
> #include "intel_crtc.h"
> #include "intel_ddi.h"
> #include "intel_de.h"
> +#include "intel_dp.h"
> #include "intel_display_types.h"
> #include "intel_fdi.h"
> #include "intel_fdi_regs.h"
> @@ -339,7 +340,9 @@ int ilk_fdi_compute_config(struct intel_crtc *crtc,
> pipe_config->fdi_lanes = lane;
>
> intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock,
> - link_bw, &pipe_config->fdi_m_n, false);
> + link_bw,
> + intel_dp_bw_fec_overhead(false),
> + &pipe_config->fdi_m_n);
>
> return 0;
> }
> --
> 2.39.2
>
