[PATCH] drm/i915/psr: enable PSR on Apple T2 eDP panels

[PATCH] drm/i915/psr: enable PSR on Apple T2 eDP panels

[Alexander Fischer]

Commit 1035f4a65f58 ("drm/i915: Disable PSR in Apple panels")
disabled PSR on all Apple sinks until i915 gained the required panel
handling.

An AUX trace on a MacBookPro16,2 running macOS 15.7.7 shows the
following writes when the panel is powered on:

  DPCD 0x321 = 0x3c
  DPCD 0x4d2 = 0x01
  DPCD 0x4d1 = 0x03
  DPCD 0x170 = 0x01 (DP_PSR_ENABLE without CRC verification)

Five seconds later, a write of 0x01 to DPCD 0x4d4 occurs between the
BanksiaTcon FIFOEnter() and SRDEnter() events. This register is the
vendor trigger for entering self refresh.

With the three setup writes, CRC verification disabled, and the 0x4d4
trigger added to i915's existing PSR enable sequence, the tested panels
enter PSR1.

Implement this handling as an i915 DPCD quirk. Limit it to Apple-OUI
eDP sinks on systems containing an Apple T2. All other Apple sinks
retain the existing NO_PSR quirk. Override the VBT PSR flag for matching
panels because Apple leaves it clear.

The same sink-side protocol may also be present on T1 and Apple silicon
systems, but leave those systems unchanged until it has been tested
with their display drivers.

Tested on MacBookPro15,1, MacBookPro15,2, MacBookPro16,1,
MacBookPro16,2 and MacBookAir9,1, covering four panel device IDs. All
five enter PSR1 after boot and across suspend/resume, report
DP_PSR_SINK_ACTIVE_SINK_SYNCED, and show no sink errors.

Tested-by: André Eikmeyer <andre.eikmeyer@kait2en.org>
Tested-by: Yossef Osman <yossef.osman@proton.me>
Signed-off-by: Alexander Fischer <alexander.fischer@kait2en.org>
---
 drivers/gpu/drm/i915/display/intel_psr.c    | 28 +++++++++++++++++--
 drivers/gpu/drm/i915/display/intel_quirks.c | 30 +++++++++++++++++++++
 drivers/gpu/drm/i915/display/intel_quirks.h |  1 +
 3 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index 5283649..be4c05e 100644
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -228,6 +228,9 @@ static bool psr_global_enabled(struct intel_dp *intel_dp)
 
 	switch (intel_dp->psr.debug & I915_PSR_DEBUG_MODE_MASK) {
 	case I915_PSR_DEBUG_DEFAULT:
+		if (intel_has_dpcd_quirk(intel_dp, QUIRK_APPLE_PSR_HANDSHAKE))
+			return true;
+
 		return intel_dp_is_edp(intel_dp) ?
 			connector->panel.vbt.psr.enable : true;
 	case I915_PSR_DEBUG_DISABLE:
@@ -663,7 +666,8 @@ static void _psr_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *co
 	drm_dbg_kms(display->drm, "eDP panel supports PSR version %x\n",
 		    connector->dp.psr_caps.dpcd[0]);
 
-	if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_NO_PSR)) {
+	if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_NO_PSR) &&
+	    !intel_has_dpcd_quirk(intel_dp, QUIRK_APPLE_PSR_HANDSHAKE)) {
 		drm_dbg_kms(display->drm,
 			    "PSR support not currently available for this panel\n");
 		return;
@@ -803,19 +807,36 @@ static void _panel_replay_enable_sink(struct intel_dp *intel_dp,
 	drm_dp_dpcd_writeb(&intel_dp->aux, PANEL_REPLAY_CONFIG3, panel_replay_config_3);
 }
 
+/* Undocumented Apple eDP sink registers */
+#define APPLE_PSR_SETUP_1	0x321
+#define APPLE_PSR_SETUP_2	0x4d2
+#define APPLE_PSR_SETUP_3	0x4d1
+#define APPLE_PSR_TRIGGER	0x4d4
+
+static void psr_apple_prepare_sink(struct intel_dp *intel_dp)
+{
+	drm_dp_dpcd_writeb(&intel_dp->aux, APPLE_PSR_SETUP_1, 0x3c);
+	drm_dp_dpcd_writeb(&intel_dp->aux, APPLE_PSR_SETUP_2, 0x01);
+	drm_dp_dpcd_writeb(&intel_dp->aux, APPLE_PSR_SETUP_3, 0x03);
+}
+
 static void _psr_enable_sink(struct intel_dp *intel_dp,
 			     const struct intel_crtc_state *crtc_state)
 {
 	struct intel_display *display = to_intel_display(intel_dp);
+	bool apple_psr = intel_has_dpcd_quirk(intel_dp, QUIRK_APPLE_PSR_HANDSHAKE);
 	u8 val = 0;
 
+	if (apple_psr)
+		psr_apple_prepare_sink(intel_dp);
+
 	if (crtc_state->has_sel_update) {
 		val |= DP_PSR_ENABLE_PSR2 | DP_PSR_IRQ_HPD_WITH_CRC_ERRORS;
 	} else {
 		if (intel_dp->psr.link_standby)
 			val |= DP_PSR_MAIN_LINK_ACTIVE;
 
-		if (DISPLAY_VER(display) >= 8)
+		if (DISPLAY_VER(display) >= 8 && !apple_psr)
 			val |= DP_PSR_CRC_VERIFICATION;
 	}
 
@@ -831,6 +852,9 @@ static void _psr_enable_sink(struct intel_dp *intel_dp,
 
 	val |= DP_PSR_ENABLE;
 	drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG, val);
+
+	if (apple_psr)
+		drm_dp_dpcd_writeb(&intel_dp->aux, APPLE_PSR_TRIGGER, 0x01);
 }
 
 static void intel_psr_enable_sink(struct intel_dp *intel_dp,
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
index 33245f4..f289161 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -9,6 +9,7 @@
 
 #include "intel_display_core.h"
 #include "intel_display_types.h"
+#include "intel_dp.h"
 #include "intel_quirks.h"
 
 static void intel_set_quirk(struct intel_display *display, enum intel_quirk_id quirk)
@@ -100,6 +101,27 @@ 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");
 }
 
+#define PCI_DEVICE_ID_APPLE_T2_BRIDGE	0x1801
+
+static void quirk_apple_psr_handshake(struct intel_dp *intel_dp)
+{
+	struct intel_display *display = to_intel_display(intel_dp);
+	struct pci_dev *t2;
+
+	if (!intel_dp_is_edp(intel_dp))
+		return;
+
+	t2 = pci_get_device(PCI_VENDOR_ID_APPLE,
+			    PCI_DEVICE_ID_APPLE_T2_BRIDGE, NULL);
+	if (!t2)
+		return;
+
+	pci_dev_put(t2);
+
+	intel_set_dpcd_quirk(intel_dp, QUIRK_APPLE_PSR_HANDSHAKE);
+	drm_info(display->drm, "Applying Apple PSR handshake quirk\n");
+}
+
 struct intel_quirk {
 	int device;
 	int subsystem_vendor;
@@ -286,6 +308,14 @@ static const struct intel_dpcd_quirk intel_dpcd_quirks[] = {
 		.sink_oui = SINK_OUI(0x00, 0x22, 0xb9),
 		.hook = quirk_disable_edp_panel_replay,
 	},
+	/* Apple T2 eDP panels */
+	{
+		.device = DEVICE_ID_ANY,
+		.subsystem_vendor = PCI_ANY_ID,
+		.subsystem_device = PCI_ANY_ID,
+		.sink_oui = SINK_OUI(0x00, 0x10, 0xfa),
+		.hook = quirk_apple_psr_handshake,
+	},
 };
 
 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 970a4fe..7b863d4 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_APPLE_PSR_HANDSHAKE,
 };
 
 void intel_init_quirks(struct intel_display *display);

base-commit: 046bcac5ed22b09812cec3b0aef678195f1eae71
-- 
2.55.0

Re: [PATCH] drm/i915/psr: enable PSR on Apple T2 eDP panels

[Lukas Wunner]

On Sat, Aug 29, 2026 at 06:16:22PM +0200, Alexander Fischer wrote:
> +static void quirk_apple_psr_handshake(struct intel_dp *intel_dp)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +	struct pci_dev *t2;
> +
> +	if (!intel_dp_is_edp(intel_dp))
> +		return;
> +
> +	t2 = pci_get_device(PCI_VENDOR_ID_APPLE,
> +			    PCI_DEVICE_ID_APPLE_T2_BRIDGE, NULL);
> +	if (!t2)
> +		return;
> +
> +	pci_dev_put(t2);

We've got pci_dev_present() for this.

Re: [PATCH] drm/i915/psr: enable PSR on Apple T2 eDP panels

[Alexander Fischer]

On Mon, 2026-08-31 at 09:19 +0200, Lukas Wunner wrote:
> We've got pci_dev_present() for this.

Thanks, will use it in v2.