[PATCH 0/2] drm/vc4: VC4 HDMI Runtime PM fixes for Packet RAM

[PATCH 0/2] drm/vc4: VC4 HDMI Runtime PM fixes for Packet RAM

[Maíra Canal]

While testing Raspberry Pi 4 HDMI hotplug with drm-misc-fixes, I hit the
following warning:

[  201.570266] ------------[ cut here ]------------
[  201.570293] Packet RAM has to be on to store the packet.
[  201.570367] WARNING: drivers/gpu/drm/vc4/vc4_hdmi.c:683 at vc4_hdmi_write_infoframe+0x404/0x494 [vc4], CPU#0: wireplumber/1606
[...]
[  201.658650] Hardware name: Raspberry Pi 4 Model B Rev 1.5 (DT)
[...]
[  201.758499] Call trace:
[  201.760967]  vc4_hdmi_write_infoframe+0x404/0x494 [vc4] (P)
[  201.766607]  vc4_hdmi_write_audio_infoframe+0x1c/0x28 [vc4]
[  201.772247]  write_infoframe+0xbc/0x140 [drm_display_helper]
[  201.777975]  drm_atomic_helper_connector_hdmi_update_audio_infoframe+0x80/0xdc [drm_display_helper]
[  201.787140]  vc4_hdmi_audio_prepare+0x4ac/0x570 [vc4]
[  201.792252]  drm_connector_hdmi_audio_prepare+0x24/0x30 [drm_display_helper]
[  201.799390]  hdmi_codec_prepare+0x100/0x160 [snd_soc_hdmi_codec]
[  201.805471]  snd_soc_pcm_dai_prepare+0xd4/0x100 [snd_soc_core]
[  201.811375]  __soc_pcm_prepare+0x60/0x12c [snd_soc_core]
[  201.816752]  soc_pcm_prepare+0x34/0x58 [snd_soc_core]
[  201.821863]  snd_pcm_do_prepare+0x70/0x8c [snd_pcm]
[  201.826798]  snd_pcm_action_nonatomic+0xe4/0x174 [snd_pcm]
[  201.832350]  snd_pcm_prepare+0xc8/0xd8 [snd_pcm]
[  201.837021]  snd_pcm_common_ioctl+0x458/0x614 [snd_pcm]
[  201.842308]  snd_pcm_ioctl+0x30/0x48 [snd_pcm]
[  201.846802]  __arm64_sys_ioctl+0x88/0xd8
[  201.850769]  invoke_syscall+0x48/0xf4
[  201.854470]  el0_svc_common+0x80/0xd8
[  201.858171]  do_el0_svc+0x1c/0x28
[  201.861520]  el0_svc+0x3c/0xb0
[  201.864605]  el0t_64_sync_handler+0x68/0xdc
[  201.868834]  el0t_64_sync+0x198/0x19c
[  201.872536] ---[ end trace 0000000000000000 ]---

Dave had already fixed this in the Raspberry Pi downstream tree [1].
This series upstreams his commits with no code changes and reworded
commit messages.

Maxime, could you ack/review these patches, please?

[1] https://github.com/raspberrypi/linux/pull/7431

Best regards,
- Maíra

---
Dave Stevenson (2):
      drm/vc4: hdmi: Move packet RAM enable to PM runtime
      drm/vc4: hdmi: Remove unused packet_ram_enabled flag

 drivers/gpu/drm/vc4/vc4_hdmi.c | 23 +++++++++++------------
 drivers/gpu/drm/vc4/vc4_hdmi.h |  6 ------
 2 files changed, 11 insertions(+), 18 deletions(-)
---
base-commit: bca45af5998a05f34b13a2ef11e639bac9c62643
change-id: 20261001-vc4-hdmi-packet-ram-fix-e4374c31f2f7

[PATCH 1/2] drm/vc4: hdmi: Move packet RAM enable to PM runtime

[Maíra Canal]

From: Dave Stevenson <dave.stevenson@raspberrypi.com>

Audio can be triggered by the HPD handler and start up before video has
been restored, calling vc4_hdmi_write_infoframe() for the audio infoframe.
vc4_hdmi_write_infoframe() needs Packet RAM to be on to store the
infoframe, however, if the video hasn't been enabled,
vc4_hdmi_encoder_post_crtc_enable() hasn't been called and therefore, the
Packet RAM can be disabled by the time vc4_hdmi_write_infoframe() executes,
causing the following splat:

[  201.570266] ------------[ cut here ]------------
[  201.570293] Packet RAM has to be on to store the packet.
[  201.570367] WARNING: drivers/gpu/drm/vc4/vc4_hdmi.c:683 at vc4_hdmi_write_infoframe+0x404/0x494 [vc4], CPU#0: wireplumber/1606
[...]
[  201.658650] Hardware name: Raspberry Pi 4 Model B Rev 1.5 (DT)
[...]
[  201.758499] Call trace:
[  201.760967]  vc4_hdmi_write_infoframe+0x404/0x494 [vc4] (P)
[  201.766607]  vc4_hdmi_write_audio_infoframe+0x1c/0x28 [vc4]
[  201.772247]  write_infoframe+0xbc/0x140 [drm_display_helper]
[  201.777975]  drm_atomic_helper_connector_hdmi_update_audio_infoframe+0x80/0xdc [drm_display_helper]
[  201.787140]  vc4_hdmi_audio_prepare+0x4ac/0x570 [vc4]
[  201.792252]  drm_connector_hdmi_audio_prepare+0x24/0x30 [drm_display_helper]
[  201.799390]  hdmi_codec_prepare+0x100/0x160 [snd_soc_hdmi_codec]
[  201.805471]  snd_soc_pcm_dai_prepare+0xd4/0x100 [snd_soc_core]
[  201.811375]  __soc_pcm_prepare+0x60/0x12c [snd_soc_core]
[  201.816752]  soc_pcm_prepare+0x34/0x58 [snd_soc_core]
[  201.821863]  snd_pcm_do_prepare+0x70/0x8c [snd_pcm]
[  201.826798]  snd_pcm_action_nonatomic+0xe4/0x174 [snd_pcm]
[  201.832350]  snd_pcm_prepare+0xc8/0xd8 [snd_pcm]
[  201.837021]  snd_pcm_common_ioctl+0x458/0x614 [snd_pcm]
[  201.842308]  snd_pcm_ioctl+0x30/0x48 [snd_pcm]
[  201.846802]  __arm64_sys_ioctl+0x88/0xd8
[  201.850769]  invoke_syscall+0x48/0xf4
[  201.854470]  el0_svc_common+0x80/0xd8
[  201.858171]  do_el0_svc+0x1c/0x28
[  201.861520]  el0_svc+0x3c/0xb0
[  201.864605]  el0t_64_sync_handler+0x68/0xdc
[  201.868834]  el0t_64_sync+0x198/0x19c
[  201.872536] ---[ end trace 0000000000000000 ]---

Considering that Packet RAM enable is essentially a power management
configuration, move its enabling/disabling to the Runtime PM hooks.

Note that post_crtc_disable() still stops all infoframes, but keeps Packet
RAM enabled, leaving it to be disabled by runtime suspend.

Link: https://github.com/raspberrypi/linux/issues/7069
Fixes: b47a72f30768 ("drm/vc4: hdmi: Switch to HDMI connector")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 17c8635c5afa..d4672aa81d85 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -894,7 +894,7 @@ static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder,
 
 	spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
 
-	HDMI_WRITE(HDMI_RAM_PACKET_CONFIG, 0);
+	HDMI_WRITE(HDMI_RAM_PACKET_CONFIG, VC4_HDMI_RAM_PACKET_ENABLE);
 
 	HDMI_WRITE(HDMI_VID_CTL, HDMI_READ(HDMI_VID_CTL) | VC4_HD_VID_CTL_CLRRGB);
 
@@ -1663,9 +1663,6 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 		WARN_ONCE(ret, "Timeout waiting for "
 			  "VC4_HDMI_SCHEDULER_CONTROL_HDMI_ACTIVE\n");
 	} else {
-		HDMI_WRITE(HDMI_RAM_PACKET_CONFIG,
-			   HDMI_READ(HDMI_RAM_PACKET_CONFIG) &
-			   ~(VC4_HDMI_RAM_PACKET_ENABLE));
 		HDMI_WRITE(HDMI_SCHEDULER_CONTROL,
 			   HDMI_READ(HDMI_SCHEDULER_CONTROL) &
 			   ~VC4_HDMI_SCHEDULER_CONTROL_MODE_HDMI);
@@ -1684,9 +1681,6 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 		WARN_ON(!(HDMI_READ(HDMI_SCHEDULER_CONTROL) &
 			  VC4_HDMI_SCHEDULER_CONTROL_HDMI_ACTIVE));
 
-		HDMI_WRITE(HDMI_RAM_PACKET_CONFIG,
-			   VC4_HDMI_RAM_PACKET_ENABLE);
-
 		spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
 		vc4_hdmi->packet_ram_enabled = true;
 
@@ -3143,6 +3137,11 @@ static int vc5_hdmi_init_resources(struct drm_device *drm,
 static int vc4_hdmi_runtime_suspend(struct device *dev)
 {
 	struct vc4_hdmi *vc4_hdmi = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
+	HDMI_WRITE(HDMI_RAM_PACKET_CONFIG, 0);
+	spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
 
 	clk_disable_unprepare(vc4_hdmi->audio_clock);
 	clk_disable_unprepare(vc4_hdmi->hsm_clock);
@@ -3153,9 +3152,8 @@ static int vc4_hdmi_runtime_suspend(struct device *dev)
 static int vc4_hdmi_runtime_resume(struct device *dev)
 {
 	struct vc4_hdmi *vc4_hdmi = dev_get_drvdata(dev);
-	unsigned long __maybe_unused flags;
+	unsigned long rate, flags;
 	u32 __maybe_unused value;
-	unsigned long rate;
 	int ret;
 
 	ret = clk_prepare_enable(vc4_hdmi->hsm_clock);
@@ -3201,6 +3199,10 @@ static int vc4_hdmi_runtime_resume(struct device *dev)
 	}
 #endif
 
+	spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
+	HDMI_WRITE(HDMI_RAM_PACKET_CONFIG, VC4_HDMI_RAM_PACKET_ENABLE);
+	spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
+
 	return 0;
 
 err_disable_clk:

-- 
2.55.0

[PATCH 2/2] drm/vc4: hdmi: Remove unused packet_ram_enabled flag

[Maíra Canal]

From: Dave Stevenson <dave.stevenson@raspberrypi.com>

The last use of the variable packet_ram_enabled was removed in commit
b47a72f30768 ("drm/vc4: hdmi: Switch to HDMI connector"), but the flag
itself wasn't. Clean it up.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 3 ---
 drivers/gpu/drm/vc4/vc4_hdmi.h | 6 ------
 2 files changed, 9 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index d4672aa81d85..939ec35527c9 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -887,8 +887,6 @@ static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder,
 
 	mutex_lock(&vc4_hdmi->mutex);
 
-	vc4_hdmi->packet_ram_enabled = false;
-
 	if (!drm_dev_enter(drm, &idx))
 		goto out;
 
@@ -1682,7 +1680,6 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 			  VC4_HDMI_SCHEDULER_CONTROL_HDMI_ACTIVE));
 
 		spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
-		vc4_hdmi->packet_ram_enabled = true;
 
 		drm_atomic_helper_connector_hdmi_update_infoframes(connector, state);
 	}
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
index 29d461d4ee49..e4ad1889cbd4 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.h
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
@@ -187,12 +187,6 @@ struct vc4_hdmi {
 	 */
 	struct drm_display_mode saved_adjusted_mode;
 
-	/**
-	 * @packet_ram_enabled: Is the HDMI controller packet RAM currently
-	 * on? Protected by @mutex.
-	 */
-	bool packet_ram_enabled;
-
 	/**
 	 * @scdc_enabled: Is the HDMI controller currently running with
 	 * the scrambler on? Protected by @mutex.

-- 
2.55.0

Re: [PATCH 1/2] drm/vc4: hdmi: Move packet RAM enable to PM runtime

[Maxime Ripard]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 421 bytes --]

On Fri, 2 Oct 2026 10:36:43 -0300, Maíra Canal wrote:
> From: Dave Stevenson <dave.stevenson@raspberrypi.com>
> 
> Audio can be triggered by the HPD handler and start up before video has
> been restored, calling vc4_hdmi_write_infoframe() for the audio infoframe.
> vc4_hdmi_write_infoframe() needs Packet RAM to be on to store the
> 
> [ ... ]

Acked-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime

Re: [PATCH 0/2] drm/vc4: VC4 HDMI Runtime PM fixes for Packet RAM

[Maíra Canal]

On Fri, 02 Oct 2026 10:36:42 -0300, Maíra Canal wrote:
> While testing Raspberry Pi 4 HDMI hotplug with drm-misc-fixes, I hit the
> following warning:
> 
> [  201.570266] ------------[ cut here ]------------
> [  201.570293] Packet RAM has to be on to store the packet.
> [  201.570367] WARNING: drivers/gpu/drm/vc4/vc4_hdmi.c:683 at vc4_hdmi_write_infoframe+0x404/0x494 [vc4], CPU#0: wireplumber/1606
> [...]
> [  201.658650] Hardware name: Raspberry Pi 4 Model B Rev 1.5 (DT)
> [...]
> [  201.758499] Call trace:
> [  201.760967]  vc4_hdmi_write_infoframe+0x404/0x494 [vc4] (P)
> [  201.766607]  vc4_hdmi_write_audio_infoframe+0x1c/0x28 [vc4]
> [  201.772247]  write_infoframe+0xbc/0x140 [drm_display_helper]
> [  201.777975]  drm_atomic_helper_connector_hdmi_update_audio_infoframe+0x80/0xdc [drm_display_helper]
> [  201.787140]  vc4_hdmi_audio_prepare+0x4ac/0x570 [vc4]
> [  201.792252]  drm_connector_hdmi_audio_prepare+0x24/0x30 [drm_display_helper]
> [  201.799390]  hdmi_codec_prepare+0x100/0x160 [snd_soc_hdmi_codec]
> [  201.805471]  snd_soc_pcm_dai_prepare+0xd4/0x100 [snd_soc_core]
> [  201.811375]  __soc_pcm_prepare+0x60/0x12c [snd_soc_core]
> [  201.816752]  soc_pcm_prepare+0x34/0x58 [snd_soc_core]
> [  201.821863]  snd_pcm_do_prepare+0x70/0x8c [snd_pcm]
> [  201.826798]  snd_pcm_action_nonatomic+0xe4/0x174 [snd_pcm]
> [  201.832350]  snd_pcm_prepare+0xc8/0xd8 [snd_pcm]
> [  201.837021]  snd_pcm_common_ioctl+0x458/0x614 [snd_pcm]
> [  201.842308]  snd_pcm_ioctl+0x30/0x48 [snd_pcm]
> [  201.846802]  __arm64_sys_ioctl+0x88/0xd8
> [  201.850769]  invoke_syscall+0x48/0xf4
> [  201.854470]  el0_svc_common+0x80/0xd8
> [  201.858171]  do_el0_svc+0x1c/0x28
> [  201.861520]  el0_svc+0x3c/0xb0
> [  201.864605]  el0t_64_sync_handler+0x68/0xdc
> [  201.868834]  el0t_64_sync+0x198/0x19c
> [  201.872536] ---[ end trace 0000000000000000 ]---
> 
> [...]

Applied to drm-misc-fixes, thanks!

[1/2] drm/vc4: hdmi: Move packet RAM enable to PM runtime
      commit: 3f57b34485dc01e5a2db60a89a6ae5439a897e53

I'll apply the second patch to drm-misc-next after the backport.

Best regards,
- Maíra