From a32f3a95413881b69c8dd319334927eb9519013c Mon Sep 17 00:00:00 2001
From: Imre Deak <imre.deak@intel.com>
Date: Tue, 20 Feb 2024 23:18:40 +0200
Subject: [PATCH] drm/i915/dp: Read DPRX for all long HPD pulses
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The TBT DP tunnel BW request logic in the Thunderbolt Connection Manager
depends on the GFX driver reading out the sink's DPRX capabilities in
response to a long HPD pulse. Since in i915 this read-out can be blocked
by another connector's/encoder's hotplug event handling (which is
serialized by drm_mode_config::connection_mutex), do a dummy DPRX read-out
in the encoder's HPD pulse handler (which is not blocked by other
encoders).
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240220211841.448846-21-imre.deak@intel.com
---
drivers/gpu/drm/i915/display/intel_dp.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 0b9c33a000f95..a0e826a740b13 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -6165,6 +6165,7 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port, bool long_hpd)
{
struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
struct intel_dp *intel_dp = &dig_port->dp;
+ u8 dpcd[DP_RECEIVER_CAP_SIZE];
if (dig_port->base.type == INTEL_OUTPUT_EDP &&
(long_hpd || !intel_pps_have_panel_power_or_vdd(intel_dp))) {
@@ -6187,6 +6188,17 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port, bool long_hpd)
dig_port->base.base.name,
long_hpd ? "long" : "short");
+ /*
+ * TBT DP tunnels require the GFX driver to read out the DPRX caps in
+ * response to long HPD pulses. The DP hotplug handler does that,
+ * however the hotplug handler may be blocked by another
+ * connector's/encoder's hotplug handler. Since the TBT CM may not
+ * complete the DP tunnel BW request for the latter connector/encoder
+ * waiting for this encoder's DPRX read, perform a dummy read here.
+ */
+ if (long_hpd)
+ intel_dp_read_dprx_caps(intel_dp, dpcd);
+
if (long_hpd) {
intel_dp->reset_link_params = true;
return IRQ_NONE;
--
2.30.2