[v2,04/11] drm/i915/ddi: Set missing TC DP PHY lane stagger delay in DDI_BUF_CTL

Commit Message

Imre Deak Feb. 14, 2025, 2:19 p.m. UTC

Add the missing PHY lane stagger delay programming for ICL-ADL
platforms on TypeC DP outputs.

v2: (Jani)
- Clarify code comment about lane stagger programming.
- Robustify macro calls with parens.

Bspec: 7534, 49533
Reviewed-by: Jani Nikula <[e-mail]>
Signed-off-by: Imre Deak <[e-mail]>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 29 ++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_reg.h          |  3 +++
 2 files changed, 32 insertions(+)

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index a09363e5dc148..1e7ae93340ff4 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -328,9 +328,32 @@  static u32 ddi_buf_phy_link_rate(int port_clock)
 	}
 }
 
+static int dp_phy_lane_stagger_delay(int port_clock)
+{
+	/*
+	 * Return the number of symbol clocks delay used to stagger the
+	 * assertion/desassertion of the port lane enables. The target delay
+	 * time is 100 ns or greater, return the number of symbols specific to
+	 * the provided port_clock (aka link clock) corresponding to this delay
+	 * time, i.e. so that
+	 *
+	 * number_of_symbols * duration_of_one_symbol >= 100 ns
+	 *
+	 * The delay must be applied only on TypeC DP outputs, for everything else
+	 * the delay must be set to 0.
+	 *
+	 * Return the number of link symbols per 100 ns:
+	 * port_clock (10 kHz) -> bits    / 100 us
+	 * / symbol_size       -> symbols / 100 us
+	 * / 1000              -> symbols / 100 ns
+	 */
+	return DIV_ROUND_UP(port_clock, intel_dp_link_symbol_size(port_clock) * 1000);
+}
+
 static void intel_ddi_init_dp_buf_reg(struct intel_encoder *encoder,
 				      const struct intel_crtc_state *crtc_state)
 {
+	struct intel_display *display = to_intel_display(encoder);
 	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
 	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
@@ -356,6 +379,12 @@  static void intel_ddi_init_dp_buf_reg(struct intel_encoder *encoder,
 		if (!intel_tc_port_in_tbt_alt_mode(dig_port))
 			intel_dp->DP |= DDI_BUF_CTL_TC_PHY_OWNERSHIP;
 	}
+
+	if (IS_DISPLAY_VER(display, 11, 13) && intel_encoder_is_tc(encoder)) {
+		int delay = dp_phy_lane_stagger_delay(crtc_state->port_clock);
+
+		intel_dp->DP |= DDI_BUF_LANE_STAGGER_DELAY(delay);
+	}
 }
 
 static int icl_calc_tbt_pll_link(struct intel_display *display,
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 3eea191f20175..50efaab3b5536 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3636,6 +3636,9 @@  enum skl_power_gate {
 #define  DDI_BUF_PORT_DATA_20BIT		REG_FIELD_PREP(DDI_BUF_PORT_DATA_MASK, 1)
 #define  DDI_BUF_PORT_DATA_40BIT		REG_FIELD_PREP(DDI_BUF_PORT_DATA_MASK, 2)
 #define  DDI_BUF_PORT_REVERSAL			(1 << 16)
+#define  DDI_BUF_LANE_STAGGER_DELAY_MASK	REG_GENMASK(15, 8)
+#define  DDI_BUF_LANE_STAGGER_DELAY(symbols)	REG_FIELD_PREP(DDI_BUF_LANE_STAGGER_DELAY_MASK, \
+							       (symbols))
 #define  DDI_BUF_IS_IDLE			(1 << 7)
 #define  DDI_BUF_CTL_TC_PHY_OWNERSHIP		REG_BIT(6)
 #define  DDI_A_4_LANES				(1 << 4)