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* [PATCH] drm/i915/display: Use PIPEDMC_FRMTMSTMP on display ver >= 30
@ 2026-05-15  8:24 Suraj Kandpal
  2026-05-15 10:21 ` Jani Nikula
                   ` (6 more replies)
  0 siblings, 7 replies; 14+ messages in thread
From: Suraj Kandpal @ 2026-05-15  8:24 UTC (permalink / raw)
  To: intel-xe, intel-gfx; +Cc: ankit.k.nautiyal, arun.r.murthy, Suraj Kandpal

Starting with display version 30, the per-pipe frame timestamp is read
from the PIPEDMC register block (PIPEDMC_FRMTMSTMP) instead of the
legacy PIPE_FRMTMSTMP MMIO. Extend PIPE_FRMTMSTMP() to take the display
and select the appropriate register based on DISPLAY_VER(), and update
all callers (intel_vblank, intel_initial_plane) accordingly.

Bspec: 79482
WA: 14022946399
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_regs.h  | 7 +++++--
 drivers/gpu/drm/i915/display/intel_initial_plane.c | 4 ++--
 drivers/gpu/drm/i915/display/intel_vblank.c        | 4 ++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_regs.h b/drivers/gpu/drm/i915/display/intel_display_regs.h
index 4321f8b529da..579f802215d3 100644
--- a/drivers/gpu/drm/i915/display/intel_display_regs.h
+++ b/drivers/gpu/drm/i915/display/intel_display_regs.h
@@ -3149,8 +3149,11 @@ enum skl_power_gate {
 /* g4x+, except vlv/chv! */
 #define _PIPE_FRMTMSTMP_A		0x70048
 #define _PIPE_FRMTMSTMP_B		0x71048
-#define PIPE_FRMTMSTMP(pipe)		\
-	_MMIO_PIPE(pipe, _PIPE_FRMTMSTMP_A, _PIPE_FRMTMSTMP_B)
+#define _PIPEDMC_FRMTMSTMP_A		0x5f0ac
+#define _PIPEDMC_FRMTMSTMP_B		0x5f4ac
+#define PIPE_FRMTMSTMP(display, pipe)	(DISPLAY_VER(display) >= 30 ? \
+	_MMIO_PIPE(pipe, _PIPEDMC_FRMTMSTMP_A, _PIPEDMC_FRMTMSTMP_B) : \
+	_MMIO_PIPE(pipe, _PIPE_FRMTMSTMP_A, _PIPE_FRMTMSTMP_B))
 
 /* g4x+, except vlv/chv! */
 #define _PIPE_FLIPTMSTMP_A		0x7004C
diff --git a/drivers/gpu/drm/i915/display/intel_initial_plane.c b/drivers/gpu/drm/i915/display/intel_initial_plane.c
index 034fe199c2a1..004cbdb6be32 100644
--- a/drivers/gpu/drm/i915/display/intel_initial_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_initial_plane.c
@@ -34,9 +34,9 @@ void intel_initial_plane_vblank_wait(struct intel_crtc *crtc)
 		return;
 	}
 
-	start_ts = intel_de_read(display, PIPE_FRMTMSTMP(crtc->pipe));
+	start_ts = intel_de_read(display, PIPE_FRMTMSTMP(display, crtc->pipe));
 
-	ret = poll_timeout_us(end_ts = intel_de_read(display, PIPE_FRMTMSTMP(crtc->pipe)),
+	ret = poll_timeout_us(end_ts = intel_de_read(display, PIPE_FRMTMSTMP(display, crtc->pipe)),
 			      end_ts != start_ts, 1000, 1000 * 1000, false);
 	if (ret)
 		drm_warn(display->drm, "[CRTC:%d:%s] early vblank wait timed out\n",
diff --git a/drivers/gpu/drm/i915/display/intel_vblank.c b/drivers/gpu/drm/i915/display/intel_vblank.c
index 28d81199792e..52ff47936f9e 100644
--- a/drivers/gpu/drm/i915/display/intel_vblank.c
+++ b/drivers/gpu/drm/i915/display/intel_vblank.c
@@ -157,7 +157,7 @@ static u32 intel_crtc_scanlines_since_frame_timestamp(struct intel_crtc *crtc)
 		 * is sampled at every start of vertical blank.
 		 */
 		scan_prev_time = intel_de_read_fw(display,
-						  PIPE_FRMTMSTMP(crtc->pipe));
+						  PIPE_FRMTMSTMP(display, crtc->pipe));
 
 		/*
 		 * The TIMESTAMP_CTR register has the current
@@ -166,7 +166,7 @@ static u32 intel_crtc_scanlines_since_frame_timestamp(struct intel_crtc *crtc)
 		scan_curr_time = intel_de_read_fw(display, IVB_TIMESTAMP_CTR);
 
 		scan_post_time = intel_de_read_fw(display,
-						  PIPE_FRMTMSTMP(crtc->pipe));
+						  PIPE_FRMTMSTMP(display, crtc->pipe));
 	} while (scan_post_time != scan_prev_time);
 
 	return div_u64(mul_u32_u32(scan_curr_time - scan_prev_time,
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 14+ messages in thread
* [PATCH] Revert "drm/i915/backlight: Remove try_vesa_interface"
@ 2026-05-15 15:53 Suraj Kandpal
  2026-05-15 16:10 ` [PATCH] drm/i915/display: Use PIPEDMC_FRMTMSTMP on display ver >= 30 Suraj Kandpal
  0 siblings, 1 reply; 14+ messages in thread
From: Suraj Kandpal @ 2026-05-15 15:53 UTC (permalink / raw)
  To: intel-xe, intel-gfx; +Cc: ankit.k.nautiyal, arun.r.murthy, Suraj Kandpal

This reverts commit 40d2f5820951dee818d05c14677277048bd85f9f.

Removing the try_vesa_interface gate caused a backlight regression on
panels whose VBT correctly reports INTEL_BACKLIGHT_DISPLAY_DDI and whose
PWM path is the actual backlight control, but whose DPCD optimistically
advertises DP_EDP_BACKLIGHT_AUX_ENABLE_CAP / _BRIGHTNESS_AUX_SET_CAP.
After the commit such panels silently bind to the VESA AUX backlight
funcs; AUX writes complete but the panel ignores them, leaving
brightness stuck (no-op backlight). Observed on at least KBL and TGL
eDP setups.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 .../drm/i915/display/intel_dp_aux_backlight.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index a8d56ebf06a2..7a6c07f6aaeb 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -691,10 +691,9 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	struct drm_device *dev = connector->base.dev;
 	struct intel_panel *panel = &connector->panel;
-	bool try_intel_interface = false;
+	bool try_intel_interface = false, try_vesa_interface = false;
 
-	/*
-	 * Check the VBT and user's module parameters to figure out which
+	/* Check the VBT and user's module parameters to figure out which
 	 * interfaces to probe
 	 */
 	switch (display->params.enable_dpcd_backlight) {
@@ -703,6 +702,7 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 	case INTEL_DP_AUX_BACKLIGHT_AUTO:
 		switch (panel->vbt.backlight.type) {
 		case INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE:
+			try_vesa_interface = true;
 			break;
 		case INTEL_BACKLIGHT_DISPLAY_DDI:
 			try_intel_interface = true;
@@ -715,12 +715,20 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 		if (panel->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)
 			try_intel_interface = true;
 
+		try_vesa_interface = true;
+		break;
+	case INTEL_DP_AUX_BACKLIGHT_FORCE_VESA:
+		try_vesa_interface = true;
 		break;
 	case INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL:
 		try_intel_interface = true;
 		break;
 	}
 
+	/* For eDP 1.5 and above we are supposed to use VESA interface for brightness control */
+	if (intel_dp->edp_dpcd[0] >= DP_EDP_15)
+		try_vesa_interface = true;
+
 	/*
 	 * Since Intel has their own backlight control interface, the majority of machines out there
 	 * using DPCD backlight controls with Intel GPUs will be using this interface as opposed to
@@ -733,9 +741,6 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 	 * panel with Intel's OUI - which is also required for us to be able to detect Intel's
 	 * backlight interface at all. This means that the only sensible way for us to detect both
 	 * interfaces is to probe for Intel's first, and VESA's second.
-	 *
-	 * Also there is a chance some VBTs may advertise false Intel backlight support even if the
-	 * TCON DPCD says otherwise. This means we keep VESA interface as fallback in that case.
 	 */
 	if (try_intel_interface && intel_dp->edp_dpcd[0] <= DP_EDP_14b &&
 	    intel_dp_aux_supports_hdr_backlight(connector)) {
@@ -745,7 +750,7 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 		return 0;
 	}
 
-	if (intel_dp_aux_supports_vesa_backlight(connector)) {
+	if (try_vesa_interface && intel_dp_aux_supports_vesa_backlight(connector)) {
 		drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Using VESA eDP backlight controls\n",
 			    connector->base.base.id, connector->base.name);
 		panel->backlight.funcs = &intel_dp_vesa_bl_funcs;
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 14+ messages in thread
end of thread, other threads:[~2026-05-19 12:02 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-05-15  8:24 [PATCH] drm/i915/display: Use PIPEDMC_FRMTMSTMP on display ver >= 30 Suraj Kandpal
2026-05-15 10:21 ` Jani Nikula
2026-05-15 15:04   ` Kandpal, Suraj
2026-05-15 10:31 ` ✓ i915.CI.BAT: success for " Patchwork
2026-05-15 14:55 ` [PATCH] " Gustavo Sousa
2026-05-15 15:07   ` Kandpal, Suraj
2026-05-15 22:10 ` ✗ i915.CI.Full: failure for " Patchwork
2026-05-17  2:45 ` [PATCH] " Suraj Kandpal
2026-05-17  3:35 ` ✓ i915.CI.BAT: success for drm/i915/display: Use PIPEDMC_FRMTMSTMP on display ver >= 30 (rev2) Patchwork
2026-05-17  5:35 ` ✗ i915.CI.Full: failure " Patchwork
  -- strict thread matches above, loose matches on Subject: below --
2026-05-15 15:53 [PATCH] Revert "drm/i915/backlight: Remove try_vesa_interface" Suraj Kandpal
2026-05-15 16:10 ` [PATCH] drm/i915/display: Use PIPEDMC_FRMTMSTMP on display ver >= 30 Suraj Kandpal
2026-05-18 14:17   ` Ville Syrjälä
2026-05-19  2:33     ` Kandpal, Suraj
2026-05-19 12:02       ` Ville Syrjälä

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