[PATCH drm-misc-next 0/3] Fixes for vc4 hotplug rework

[PATCH drm-misc-next 0/3] Fixes for vc4 hotplug rework

[Danilo Krummrich]

Hi,

I've found a few potential issues left after the hotplug rework.

In vc4_hdmi.c we're missing two mutex_unlock() calls when the device is
unplugged.

vc4_crtc and vc4_plane seem to miss some drm_dev_enter()/drm_dev_exit() calls
to protect against resource access after the device/driver is unbound, but the
DRM potentially isn't freed yet and userspace can still call into the driver.

Danilo Krummrich (3):
  drm/vc4: hdmi: unlock mutex when device is unplugged
  drm/vc4: plane: protect device resources after removal
  drm/vc4: crtc: protect device resources after removal

 drivers/gpu/drm/vc4/vc4_crtc.c  | 41 ++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/vc4/vc4_drv.h   |  1 +
 drivers/gpu/drm/vc4/vc4_hdmi.c  |  7 ++++--
 drivers/gpu/drm/vc4/vc4_plane.c | 25 ++++++++++++++++++++
 4 files changed, 71 insertions(+), 3 deletions(-)


base-commit: 8ba9249396bef37cb68be9e8dee7847f1737db9d
-- 
2.37.2

[PATCH drm-misc-next 1/3] drm/vc4: hdmi: unlock mutex when device is unplugged

[Danilo Krummrich]

In vc4_hdmi_encoder_{pre,post}_crtc_enable() commit cd00ed5187bf
("drm/vc4: hdmi: Protect device resources after removal") missed to
unlock the mutex before returning due to drm_dev_enter() indicating the
device being unplugged.

Fixes: cd00ed5187bf ("drm/vc4: hdmi: Protect device resources after removal")
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 84e5a91c2ea7..4d3ff51ad2a8 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1425,7 +1425,7 @@ static void vc4_hdmi_encoder_pre_crtc_enable(struct drm_encoder *encoder,
 	mutex_lock(&vc4_hdmi->mutex);
 
 	if (!drm_dev_enter(drm, &idx))
-		return;
+		goto out;
 
 	if (vc4_hdmi->variant->csc_setup)
 		vc4_hdmi->variant->csc_setup(vc4_hdmi, conn_state, mode);
@@ -1436,6 +1436,7 @@ static void vc4_hdmi_encoder_pre_crtc_enable(struct drm_encoder *encoder,
 
 	drm_dev_exit(idx);
 
+out:
 	mutex_unlock(&vc4_hdmi->mutex);
 }
 
@@ -1455,7 +1456,7 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 	mutex_lock(&vc4_hdmi->mutex);
 
 	if (!drm_dev_enter(drm, &idx))
-		return;
+		goto out;
 
 	spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
 
@@ -1516,6 +1517,8 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 	vc4_hdmi_enable_scrambling(encoder);
 
 	drm_dev_exit(idx);
+
+out:
 	mutex_unlock(&vc4_hdmi->mutex);
 }
 
-- 
2.37.2

[PATCH drm-misc-next 2/3] drm/vc4: plane: protect device resources after removal

[Danilo Krummrich]

(Hardware) resources which are bound to the driver and device lifecycle
must not be accessed after the device and driver are unbound.

However, the DRM device isn't freed as long as the last user closed it,
hence userspace can still call into the driver.

Therefore protect the critical sections which are accessing those
resources with drm_dev_enter() and drm_dev_exit().

Fixes: 9872c7a31921 ("drm/vc4: plane: Switch to drmm_universal_plane_alloc()")
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
 drivers/gpu/drm/vc4/vc4_drv.h   |  1 +
 drivers/gpu/drm/vc4/vc4_plane.c | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 418a8242691f..80da9a9337cc 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -341,6 +341,7 @@ struct vc4_hvs {
 
 struct vc4_plane {
 	struct drm_plane base;
+	struct drm_device *dev;
 };
 
 static inline struct vc4_plane *
diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index eff9c63adfa7..cb13bb583546 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -19,6 +19,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_atomic_uapi.h>
 #include <drm/drm_blend.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_fb_dma_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
@@ -1218,14 +1219,22 @@ static void vc4_plane_atomic_update(struct drm_plane *plane,
 u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist)
 {
 	struct vc4_plane_state *vc4_state = to_vc4_plane_state(plane->state);
+	struct vc4_plane *vc4_plane = to_vc4_plane(plane);
 	int i;
+	int idx;
 
 	vc4_state->hw_dlist = dlist;
 
+	if (!drm_dev_enter(vc4_plane->dev, &idx))
+		goto out;
+
 	/* Can't memcpy_toio() because it needs to be 32-bit writes. */
 	for (i = 0; i < vc4_state->dlist_count; i++)
 		writel(vc4_state->dlist[i], &dlist[i]);
 
+	drm_dev_exit(idx);
+
+out:
 	return vc4_state->dlist_count;
 }
 
@@ -1243,8 +1252,10 @@ u32 vc4_plane_dlist_size(const struct drm_plane_state *state)
 void vc4_plane_async_set_fb(struct drm_plane *plane, struct drm_framebuffer *fb)
 {
 	struct vc4_plane_state *vc4_state = to_vc4_plane_state(plane->state);
+	struct vc4_plane *vc4_plane = to_vc4_plane(plane);
 	struct drm_gem_dma_object *bo = drm_fb_dma_get_gem_obj(fb, 0);
 	uint32_t addr;
+	int idx;
 
 	/* We're skipping the address adjustment for negative origin,
 	 * because this is only called on the primary plane.
@@ -1252,12 +1263,17 @@ void vc4_plane_async_set_fb(struct drm_plane *plane, struct drm_framebuffer *fb)
 	WARN_ON_ONCE(plane->state->crtc_x < 0 || plane->state->crtc_y < 0);
 	addr = bo->dma_addr + fb->offsets[0];
 
+	if (!drm_dev_enter(vc4_plane->dev, &idx))
+		return;
+
 	/* Write the new address into the hardware immediately.  The
 	 * scanout will start from this address as soon as the FIFO
 	 * needs to refill with pixels.
 	 */
 	writel(addr, &vc4_state->hw_dlist[vc4_state->ptr0_offset]);
 
+	drm_dev_exit(idx);
+
 	/* Also update the CPU-side dlist copy, so that any later
 	 * atomic updates that don't do a new modeset on our plane
 	 * also use our updated address.
@@ -1271,6 +1287,8 @@ static void vc4_plane_atomic_async_update(struct drm_plane *plane,
 	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state,
 										 plane);
 	struct vc4_plane_state *vc4_state, *new_vc4_state;
+	struct vc4_plane *vc4_plane = to_vc4_plane(plane);
+	int idx;
 
 	swap(plane->state->fb, new_plane_state->fb);
 	plane->state->crtc_x = new_plane_state->crtc_x;
@@ -1323,6 +1341,9 @@ static void vc4_plane_atomic_async_update(struct drm_plane *plane,
 	vc4_state->dlist[vc4_state->ptr0_offset] =
 		new_vc4_state->dlist[vc4_state->ptr0_offset];
 
+	if (!drm_dev_enter(vc4_plane->dev, &idx))
+		return;
+
 	/* Note that we can't just call vc4_plane_write_dlist()
 	 * because that would smash the context data that the HVS is
 	 * currently using.
@@ -1333,6 +1354,8 @@ static void vc4_plane_atomic_async_update(struct drm_plane *plane,
 	       &vc4_state->hw_dlist[vc4_state->pos2_offset]);
 	writel(vc4_state->dlist[vc4_state->ptr0_offset],
 	       &vc4_state->hw_dlist[vc4_state->ptr0_offset]);
+
+	drm_dev_exit(idx);
 }
 
 static int vc4_plane_atomic_async_check(struct drm_plane *plane,
@@ -1521,6 +1544,8 @@ struct drm_plane *vc4_plane_init(struct drm_device *dev,
 					       modifiers, type, NULL);
 	if (IS_ERR(vc4_plane))
 		return ERR_CAST(vc4_plane);
+
+	vc4_plane->dev = dev;
 	plane = &vc4_plane->base;
 
 	if (vc4->is_vc5)
-- 
2.37.2

[PATCH drm-misc-next 3/3] drm/vc4: crtc: protect device resources after removal

[Danilo Krummrich]

(Hardware) resources which are bound to the driver and device lifecycle
must not be accessed after the device and driver are unbound.

However, the DRM device isn't freed as long as the last user closed it,
hence userspace can still call into the driver.

Therefore protect the critical sections which are accessing those
resources with drm_dev_enter() and drm_dev_exit().

Fixes: 7cc4214c27cf ("drm/vc4: crtc: Switch to drmm_kzalloc")
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 41 +++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 2def6e2ad6f0..51daf190196e 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -39,6 +39,7 @@
 #include <drm/drm_atomic_uapi.h>
 #include <drm/drm_fb_dma_helper.h>
 #include <drm/drm_framebuffer.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_vblank.h>
@@ -295,10 +296,17 @@ struct drm_encoder *vc4_get_crtc_encoder(struct drm_crtc *crtc,
 static void vc4_crtc_pixelvalve_reset(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct drm_device *dev = crtc->dev;
+	int idx;
+
+	if (!drm_dev_enter(dev, &idx))
+		return;
 
 	/* The PV needs to be disabled before it can be flushed */
 	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) & ~PV_CONTROL_EN);
 	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) | PV_CONTROL_FIFO_CLR);
+
+	drm_dev_exit(idx);
 }
 
 static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encoder,
@@ -321,6 +329,10 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encode
 	u32 format = is_dsi1 ? PV_CONTROL_FORMAT_DSIV_24 : PV_CONTROL_FORMAT_24;
 	u8 ppc = pv_data->pixels_per_clock;
 	bool debug_dump_regs = false;
+	int idx;
+
+	if (!drm_dev_enter(dev, &idx))
+		return;
 
 	if (debug_dump_regs) {
 		struct drm_printer p = drm_info_printer(&vc4_crtc->pdev->dev);
@@ -410,6 +422,8 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encode
 			 drm_crtc_index(crtc));
 		drm_print_regset32(&p, &vc4_crtc->regset);
 	}
+
+	drm_dev_exit(idx);
 }
 
 static void require_hvs_enabled(struct drm_device *dev)
@@ -430,13 +444,18 @@ static int vc4_crtc_disable(struct drm_crtc *crtc,
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
 	struct drm_device *dev = crtc->dev;
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
-	int ret;
+	int idx, ret;
+
+	if (!drm_dev_enter(dev, &idx))
+		return -ENODEV;
 
 	CRTC_WRITE(PV_V_CONTROL,
 		   CRTC_READ(PV_V_CONTROL) & ~PV_VCONTROL_VIDEN);
 	ret = wait_for(!(CRTC_READ(PV_V_CONTROL) & PV_VCONTROL_VIDEN), 1);
 	WARN_ONCE(ret, "Timeout waiting for !PV_VCONTROL_VIDEN\n");
 
+	drm_dev_exit(idx);
+
 	/*
 	 * This delay is needed to avoid to get a pixel stuck in an
 	 * unflushable FIFO between the pixelvalve and the HDMI
@@ -588,6 +607,7 @@ static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
 	struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, new_state);
 	struct vc4_encoder *vc4_encoder = to_vc4_encoder(encoder);
+	int idx;
 
 	drm_dbg(dev, "Enabling CRTC %s (%u) connected to Encoder %s (%u)",
 		crtc->name, crtc->base.id, encoder->name, encoder->base.id);
@@ -606,6 +626,9 @@ static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
 
 	vc4_crtc_config_pv(crtc, encoder, state);
 
+	if (!drm_dev_enter(dev, &idx))
+		return;
+
 	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) | PV_CONTROL_EN);
 
 	if (vc4_encoder->pre_crtc_enable)
@@ -617,6 +640,8 @@ static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
 	CRTC_WRITE(PV_V_CONTROL,
 		   CRTC_READ(PV_V_CONTROL) | PV_VCONTROL_VIDEN);
 
+	drm_dev_exit(idx);
+
 	if (vc4_encoder->post_crtc_enable)
 		vc4_encoder->post_crtc_enable(encoder, state);
 }
@@ -711,17 +736,31 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
 static int vc4_enable_vblank(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct drm_device *dev = crtc->dev;
+	int idx;
+
+	if (!drm_dev_enter(dev, &idx))
+		return -ENODEV;
 
 	CRTC_WRITE(PV_INTEN, PV_INT_VFP_START);
 
+	drm_dev_exit(idx);
+
 	return 0;
 }
 
 static void vc4_disable_vblank(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct drm_device *dev = crtc->dev;
+	int idx;
+
+	if (!drm_dev_enter(dev, &idx))
+		return;
 
 	CRTC_WRITE(PV_INTEN, 0);
+
+	drm_dev_exit(idx);
 }
 
 static void vc4_crtc_handle_page_flip(struct vc4_crtc *vc4_crtc)
-- 
2.37.2

Re: [PATCH drm-misc-next 2/3] drm/vc4: plane: protect device resources after removal

[Maxime Ripard]

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Hi,

On Fri, Aug 19, 2022 at 02:29:04AM +0200, Danilo Krummrich wrote:
> (Hardware) resources which are bound to the driver and device lifecycle
> must not be accessed after the device and driver are unbound.
> 
> However, the DRM device isn't freed as long as the last user closed it,
> hence userspace can still call into the driver.
> 
> Therefore protect the critical sections which are accessing those
> resources with drm_dev_enter() and drm_dev_exit().

Ah good catch, thanks

> Fixes: 9872c7a31921 ("drm/vc4: plane: Switch to drmm_universal_plane_alloc()")
> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> ---
>  drivers/gpu/drm/vc4/vc4_drv.h   |  1 +
>  drivers/gpu/drm/vc4/vc4_plane.c | 25 +++++++++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index 418a8242691f..80da9a9337cc 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -341,6 +341,7 @@ struct vc4_hvs {
>  
>  struct vc4_plane {
>  	struct drm_plane base;
> +	struct drm_device *dev;

That pointer already exists in struct drm_plane

Looks good otherwise

Maxime

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Re: [PATCH drm-misc-next 3/3] drm/vc4: crtc: protect device resources after removal

[Maxime Ripard]

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Hi,

On Fri, Aug 19, 2022 at 02:29:05AM +0200, Danilo Krummrich wrote:
> (Hardware) resources which are bound to the driver and device lifecycle
> must not be accessed after the device and driver are unbound.
> 
> However, the DRM device isn't freed as long as the last user closed it,
> hence userspace can still call into the driver.
> 
> Therefore protect the critical sections which are accessing those
> resources with drm_dev_enter() and drm_dev_exit().
> 
> Fixes: 7cc4214c27cf ("drm/vc4: crtc: Switch to drmm_kzalloc")
> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c | 41 +++++++++++++++++++++++++++++++++-
>  1 file changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 2def6e2ad6f0..51daf190196e 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -39,6 +39,7 @@
>  #include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_fb_dma_helper.h>
>  #include <drm/drm_framebuffer.h>
> +#include <drm/drm_drv.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
>  #include <drm/drm_vblank.h>
> @@ -295,10 +296,17 @@ struct drm_encoder *vc4_get_crtc_encoder(struct drm_crtc *crtc,
>  static void vc4_crtc_pixelvalve_reset(struct drm_crtc *crtc)
>  {
>  	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +	struct drm_device *dev = crtc->dev;
> +	int idx;
> +
> +	if (!drm_dev_enter(dev, &idx))
> +		return;
>  
>  	/* The PV needs to be disabled before it can be flushed */
>  	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) & ~PV_CONTROL_EN);
>  	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) | PV_CONTROL_FIFO_CLR);
> +
> +	drm_dev_exit(idx);
>  }
>  
>  static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encoder,
> @@ -321,6 +329,10 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encode
>  	u32 format = is_dsi1 ? PV_CONTROL_FORMAT_DSIV_24 : PV_CONTROL_FORMAT_24;
>  	u8 ppc = pv_data->pixels_per_clock;
>  	bool debug_dump_regs = false;
> +	int idx;
> +
> +	if (!drm_dev_enter(dev, &idx))
> +		return;
>  
>  	if (debug_dump_regs) {
>  		struct drm_printer p = drm_info_printer(&vc4_crtc->pdev->dev);
> @@ -410,6 +422,8 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc, struct drm_encoder *encode
>  			 drm_crtc_index(crtc));
>  		drm_print_regset32(&p, &vc4_crtc->regset);
>  	}
> +
> +	drm_dev_exit(idx);
>  }
>  
>  static void require_hvs_enabled(struct drm_device *dev)
> @@ -430,13 +444,18 @@ static int vc4_crtc_disable(struct drm_crtc *crtc,
>  	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
>  	struct drm_device *dev = crtc->dev;
>  	struct vc4_dev *vc4 = to_vc4_dev(dev);
> -	int ret;
> +	int idx, ret;
> +
> +	if (!drm_dev_enter(dev, &idx))
> +		return -ENODEV;
>  
>  	CRTC_WRITE(PV_V_CONTROL,
>  		   CRTC_READ(PV_V_CONTROL) & ~PV_VCONTROL_VIDEN);
>  	ret = wait_for(!(CRTC_READ(PV_V_CONTROL) & PV_VCONTROL_VIDEN), 1);
>  	WARN_ONCE(ret, "Timeout waiting for !PV_VCONTROL_VIDEN\n");
>  
> +	drm_dev_exit(idx);
> +

I think this would be easier to follow if we were protecting the entire
function with our lock.

Having locks taken in the middle of the function is harder to identify
whether or not one particular function is safe or not.

The same applies to the plane patch

Maxime

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Re: [PATCH drm-misc-next 2/3] drm/vc4: plane: protect device resources after removal

[Danilo Krummrich]

Hi Maxime,

On 8/19/22 09:26, Maxime Ripard wrote:
> Hi,
> 
> On Fri, Aug 19, 2022 at 02:29:04AM +0200, Danilo Krummrich wrote:
>> (Hardware) resources which are bound to the driver and device lifecycle
>> must not be accessed after the device and driver are unbound.
>>
>> However, the DRM device isn't freed as long as the last user closed it,
>> hence userspace can still call into the driver.
>>
>> Therefore protect the critical sections which are accessing those
>> resources with drm_dev_enter() and drm_dev_exit().
> 
> Ah good catch, thanks
> 
>> Fixes: 9872c7a31921 ("drm/vc4: plane: Switch to drmm_universal_plane_alloc()")
>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>> ---
>>   drivers/gpu/drm/vc4/vc4_drv.h   |  1 +
>>   drivers/gpu/drm/vc4/vc4_plane.c | 25 +++++++++++++++++++++++++
>>   2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
>> index 418a8242691f..80da9a9337cc 100644
>> --- a/drivers/gpu/drm/vc4/vc4_drv.h
>> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
>> @@ -341,6 +341,7 @@ struct vc4_hvs {
>>   
>>   struct vc4_plane {
>>   	struct drm_plane base;
>> +	struct drm_device *dev;
> 
> That pointer already exists in struct drm_plane
Oops, I've sent a v2. Also addressing your comment from the other patch.

- Danilo
> 
> Looks good otherwise
> 
> Maxime