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From: Maarten Lankhorst <dev@lankhorst.se>
To: intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org,
	Maarten Lankhorst <dev@lankhorst.se>,
	Uma Shankar <uma.shankar@intel.com>
Subject: [PATCH v7 07/26] drm/i915/display: Handle vlv dsi workaround in scanline_in_safe_range too
Date: Tue, 10 Mar 2026 12:56:49 +0100	[thread overview]
Message-ID: <20260310115709.2276203-8-dev@lankhorst.se> (raw)
In-Reply-To: <20260310115709.2276203-1-dev@lankhorst.se>

Now that we have a macro, might as well handle the VLV dsi workaround
too.

This makes the vblank evasion code slightly more deterministic, by not
looping with interrupts disabled.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
---
 drivers/gpu/drm/i915/display/intel_vblank.c | 36 ++++++++++-----------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vblank.c b/drivers/gpu/drm/i915/display/intel_vblank.c
index 73676d8ccec8b..3eb6418723a84 100644
--- a/drivers/gpu/drm/i915/display/intel_vblank.c
+++ b/drivers/gpu/drm/i915/display/intel_vblank.c
@@ -739,6 +739,24 @@ static bool scanline_in_safe_range(struct intel_vblank_evade_ctx *evade, int *sc
 	else
 		*scanline = __intel_get_crtc_scanline(evade->crtc);
 
+	/*
+	 * On VLV/CHV DSI the scanline counter would appear to
+	 * increment approx. 1/3 of a scanline before start of vblank.
+	 * The registers still get latched at start of vblank however.
+	 * This means we must not write any registers on the first
+	 * line of vblank (since not the whole line is actually in
+	 * vblank). And unfortunately we can't use the interrupt to
+	 * wait here since it will fire too soon. We could use the
+	 * frame start interrupt instead since it will fire after the
+	 * critical scanline, but that would require more changes
+	 * in the interrupt code. So for now we'll just do the nasty
+	 * thing and poll for the bad scanline to pass us by.
+	 *
+	 * FIXME figure out if BXT+ DSI suffers from this as well
+	 */
+	if (evade->need_vlv_dsi_wa && *scanline == evade->vblank_start)
+		return false;
+
 	return *scanline < evade->min || *scanline > evade->max;
 }
 
@@ -769,24 +787,6 @@ int intel_vblank_evade(struct intel_vblank_evade_ctx *evade)
 		local_irq_disable();
 	}
 
-	/*
-	 * On VLV/CHV DSI the scanline counter would appear to
-	 * increment approx. 1/3 of a scanline before start of vblank.
-	 * The registers still get latched at start of vblank however.
-	 * This means we must not write any registers on the first
-	 * line of vblank (since not the whole line is actually in
-	 * vblank). And unfortunately we can't use the interrupt to
-	 * wait here since it will fire too soon. We could use the
-	 * frame start interrupt instead since it will fire after the
-	 * critical scanline, but that would require more changes
-	 * in the interrupt code. So for now we'll just do the nasty
-	 * thing and poll for the bad scanline to pass us by.
-	 *
-	 * FIXME figure out if BXT+ DSI suffers from this as well
-	 */
-	while (evade->need_vlv_dsi_wa && scanline == evade->vblank_start)
-		scanline = intel_get_crtc_scanline(crtc);
-
 	return scanline;
 }
 
-- 
2.51.0


  parent reply	other threads:[~2026-03-10 11:57 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-10 11:56 [PATCH v7 00/26] drm/i915/display: All patches to make PREEMPT_RT work on i915 + xe Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 01/26] drm/vblank_work: Add methods to schedule vblank_work in 2 stages Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 02/26] drm/vblank: Add a 2-stage version of drm_crtc_arm_vblank_event Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 03/26] drm/intel/display: Make intel_crtc_arm_vblank_event static Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 04/26] drm/intel/display: Convert vblank event handling to 2-stage arming Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 05/26] drm/i915/display: Move vblank put until after critical section Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 06/26] drm/i915/display: Remove locking from intel_vblank_evade " Maarten Lankhorst
2026-03-10 11:56 ` Maarten Lankhorst [this message]
2026-03-10 11:56 ` [PATCH v7 08/26] drm/i915: Use preempt_disable/enable_rt() where recommended Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 09/26] drm/i915/display: Make get_vblank_counter use intel_de_read_fw() Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 10/26] drm/i915/display: Do not take uncore lock in i915_get_vblank_counter Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 11/26] drm/i915/display: Make icl_dsi_frame_update use _fw too Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 12/26] drm/i915/display: Use intel_de_read/write_fw in colorops Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 13/26] drm/i915/display: Use intel_de_write_fw in intel_pipe_fastset Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 14/26] drm/i915/display: Make set_pipeconf use the fw variants Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 15/26] drm/i915/display: Fix intel_lpe_audio_irq_handler for PREEMPT-RT Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 16/26] drm/i915/gt: Use spin_lock_irq() instead of local_irq_disable() + spin_lock() Maarten Lankhorst
2026-03-10 11:56 ` [PATCH v7 17/26] drm/i915: Drop the irqs_disabled() check Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 18/26] drm/i915/guc: Consider also RCU depth in busy loop Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 19/26] drm/i915/gt: Fix selftests on PREEMPT_RT Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 20/26] drm/i915/gt: Set stop_timeout() correctly on PREEMPT-RT Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 21/26] drm/i915/display: Remove uncore lock from vlv_atomic_update_fifo Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 22/26] drm/i915: Use sleeping selftests for igt_atomic on PREEMPT_RT Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 23/26] Revert "drm/i915: Depend on !PREEMPT_RT." Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 24/26] PREEMPT_RT injection Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 25/26] FOR-CI: bump MAX_STACK_TRACE_ENTRIES Maarten Lankhorst
2026-03-10 11:57 ` [PATCH v7 26/26] drm/i915/gt: Add a spinlock to prevent starvation of irq_work Maarten Lankhorst
2026-03-10 17:04   ` Sebastian Andrzej Siewior
2026-03-10 18:14     ` Maarten Lankhorst
2026-03-10 17:22   ` Sebastian Andrzej Siewior
2026-03-10 19:03     ` Maarten Lankhorst
2026-03-11  3:21 ` Claude review: drm/i915/display: All patches to make PREEMPT_RT work on i915 + xe Claude Code Review Bot

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