linux-kernel - Re: [PATCH 1/2] drm: introduce page_flip

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Message-ID: <aXto53g2mSNsNmFM@hal-station>
Date: Thu, 29 Jan 2026 09:04:23 -0500
From: Hamza Mahfooz <someguy@...ective-light.com>
To: Christian König <christian.koenig@....com>
Cc: Timur Kristóf <timur.kristof@...il.com>,
	Alex Deucher <alexdeucher@...il.com>,
	Michel Dänzer <michel.daenzer@...lbox.org>,
	Mario Limonciello <mario.limonciello@....com>,
	dri-devel@...ts.freedesktop.org,
	Alex Deucher <alexander.deucher@....com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Harry Wentland <harry.wentland@....com>,
	Leo Li <sunpeng.li@....com>, Rodrigo Siqueira <siqueira@...lia.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Sunil Khatri <sunil.khatri@....com>, Ce Sun <cesun102@....com>,
	Lijo Lazar <lijo.lazar@....com>,
	Kenneth Feng <kenneth.feng@....com>,
	Ivan Lipski <ivan.lipski@....com>, Alex Hung <alex.hung@....com>,
	Tom Chung <chiahsuan.chung@....com>, Melissa Wen <mwen@...lia.com>,
	Fangzhi Zuo <Jerry.Zuo@....com>, amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm: introduce page_flip_timeout()

On Thu, Jan 29, 2026 at 01:59:00PM +0100, Christian König wrote:
> > How do you propose to do that?
> 
> I need to dig a bit into the DAL/DC code and see how the signaling path actually goes.
> 
> Going to give that a try tomorrow.
> 

For recent ASICs, something along the lines of the following should do
the trick:

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
index dc8d2f52c7d6..fac668c2fcfb 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
@@ -510,6 +510,7 @@ struct amdgpu_crtc {
 	bool wb_pending;
 	bool wb_enabled;
 	struct drm_writeback_connector *wb_conn;
+	int pflip_cnt;
 };
 
 struct amdgpu_encoder_atom_dig {
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 740711ac1037..1c3b7fbab1c6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -427,6 +427,18 @@ static inline bool update_planes_and_stream_adapter(struct dc *dc,
 					   stream_update);
 }
 
+static inline bool update_pflip_cnt(struct amdgpu_crtc *acrtc)
+{
+	int cnt = acrtc->pflip_cnt++;
+
+	if (cnt == 300) {
+		acrtc->pflip_cnt = 0;
+		return true;
+	}
+
+	return false;
+}
+
 /**
  * dm_pflip_high_irq() - Handle pageflip interrupt
  * @interrupt_params: ignored
@@ -454,6 +466,9 @@ static void dm_pflip_high_irq(void *interrupt_params)
 		return;
 	}
 
+	if (update_pflip_cnt(amdgpu_crtc))
+		return;
+
 	spin_lock_irqsave(&adev_to_drm(adev)->event_lock, flags);
 
 	if (amdgpu_crtc->pflip_status != AMDGPU_FLIP_SUBMITTED) {
@@ -589,6 +604,9 @@ static void dm_vupdate_high_irq(void *interrupt_params)
 	acrtc = get_crtc_by_otg_inst(adev, irq_params->irq_src - IRQ_TYPE_VUPDATE);
 
 	if (acrtc) {
+		if (update_pflip_cnt(acrtc))
+			return;
+
 		vrr_active = amdgpu_dm_crtc_vrr_active_irq(acrtc);
 		drm_dev = acrtc->base.dev;
 		vblank = drm_crtc_vblank_crtc(&acrtc->base);
@@ -659,6 +677,9 @@ static void dm_crtc_high_irq(void *interrupt_params)
 	if (!acrtc)
 		return;
 
+	if (update_pflip_cnt(acrtc))
+		return;
+
 	if (acrtc->wb_conn) {
 		spin_lock_irqsave(&acrtc->wb_conn->job_lock, flags);