[PATCH v2] drm/i915/display: Add quirk for interlane align bit on CH7511

[Patrik Jakobsson <pjakobsson@suse.de>]

When disabling pattern training after successful link training the
CH7511 bridge incorrectly clears the INTERLANE_ALIGN_DONE bit. This is
interpreted as link failure when rechecking the link status and triggers
an endless loop of retraining sequences.

This patch adds a quirk to pretend the bit is still set and no
retraining is needed.

Fixes: 3b3be899fc81 ("drm/i915/dp: Recheck link state after modeset")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/15744
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---

v2 changes:
    - Added "Closes" tag

 drivers/gpu/drm/i915/display/intel_dp.c     |  9 +++++++++
 drivers/gpu/drm/i915/display/intel_quirks.c | 17 +++++++++++++++++
 drivers/gpu/drm/i915/display/intel_quirks.h |  1 +
 3 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 85d3aa3b9894..5b269b1f18d7 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5875,6 +5875,15 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 	if (intel_dp->link.seq_train_failures)
 		return true;
 
+	/*
+	 * The CH7511 bridge incorrectly clears the INTERLANE_ALIGN_DONE bit
+	 * when disabling training pattern.
+	 */
+	if (intel_has_dpcd_quirk(intel_dp, QUIRK_IGNORE_INTERLANE_ALIGN_BIT)) {
+		link_status[DP_LANE_ALIGN_STATUS_UPDATED - DP_LANE0_1_STATUS] |=
+			DP_INTERLANE_ALIGN_DONE;
+	}
+
 	/* Retrain if link not ok */
 	return !intel_dp_link_ok(intel_dp, link_status) &&
 		!intel_psr_link_ok(intel_dp);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
index 33245f44c0d5..2cec0a945528 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -100,6 +100,14 @@ static void quirk_disable_psr2(struct intel_display *display)
 	drm_info(display->drm, "PSR2 support not currently available for this setup, applying disable PSR2 quirk\n");
 }
 
+static void quirk_ignore_interlane_align_bit(struct intel_dp *intel_dp)
+{
+	struct intel_display *display = to_intel_display(intel_dp);
+
+	intel_set_dpcd_quirk(intel_dp, QUIRK_IGNORE_INTERLANE_ALIGN_BIT);
+	drm_info(display->drm, "Applying ignore interlane align bit quirk\n");
+}
+
 struct intel_quirk {
 	int device;
 	int subsystem_vendor;
@@ -286,6 +294,15 @@ static const struct intel_dpcd_quirk intel_dpcd_quirks[] = {
 		.sink_oui = SINK_OUI(0x00, 0x22, 0xb9),
 		.hook = quirk_disable_edp_panel_replay,
 	},
+	/* Nodka TPC6000-C152 */
+	{
+		.device = 0x0f31,
+		.subsystem_vendor = 0x8086,
+		.subsystem_device = 0x0f31,
+		.sink_oui = SINK_OUI(0x2b, 0x02, 0xf0),
+		.sink_device_id = SINK_DEVICE_ID('C', 'H', '7', '5', '1', '1'),
+		.hook = quirk_ignore_interlane_align_bit,
+	},
 };
 
 void intel_init_quirks(struct intel_display *display)
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h b/drivers/gpu/drm/i915/display/intel_quirks.h
index 970a4fe52faf..7fcc3967f84f 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -23,6 +23,7 @@ enum intel_quirk_id {
 	QUIRK_EDP_LIMIT_RATE_HBR2,
 	QUIRK_DISABLE_EDP_PANEL_REPLAY,
 	QUIRK_DISABLE_PSR2,
+	QUIRK_IGNORE_INTERLANE_ALIGN_BIT,
 };
 
 void intel_init_quirks(struct intel_display *display);
-- 
2.54.0