[PATCH 12/32] drm/i915/dp: Pass actual BW overhead to m_n calculation
Imre Deak
imre.deak at intel.com
Tue Nov 7 14:49:40 UTC 2023
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.
v2:
- Fix passing the correct crtc_state->fec_enable param in
intel_dp_mst_compute_link_config() /
intel_dp_dsc_mst_compute_link_config().
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com> (v1)
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
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 9e9c03287869b..3c7ef2cc3b8b1 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2389,17 +2389,45 @@ 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.
*
@@ -2409,7 +2437,7 @@ 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 cae2a3b12e20d..6d0636acb7250 100644
--- a/drivers/gpu/drm/i915/display/intel_display.h
+++ b/drivers/gpu/drm/i915/display/intel_display.h
@@ -394,8 +394,8 @@ 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 0bbd125c72b42..d3c4f9495ca65 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 28db1775d3a5d..1f6fbab7d4ada 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -180,8 +180,8 @@ 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->fec_enable),
+ &crtc_state->dp_m_n);
crtc_state->dp_m_n.tu = slots;
return 0;
@@ -275,8 +275,8 @@ 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->fec_enable),
+ &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
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