[PATCH] drm/panthor: Don't add write fences to the shared BOs

[PATCH] drm/panthor: Don't add write fences to the shared BOs

[Boris Brezillon]

The only user (the mesa gallium driver) is already assuming explicit
synchronization and doing the export/import dance on shared BOs. The
only reason we were registering ourselves as writers on external BOs
is because Xe, which was the reference back when we developed Panthor,
was doing so. Turns out Xe was wrong, and we really want bookkeep on
all registered fences, so userspace can explicitly upgrade those to
read/write when needed.

Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_sched.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 9a0ff48f7061..41260cf4beb8 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -3423,13 +3423,8 @@ void panthor_job_update_resvs(struct drm_exec *exec, struct drm_sched_job *sched
 {
 	struct panthor_job *job = container_of(sched_job, struct panthor_job, base);
 
-	/* Still not sure why we want USAGE_WRITE for external objects, since I
-	 * was assuming this would be handled through explicit syncs being imported
-	 * to external BOs with DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but other drivers
-	 * seem to pass DMA_RESV_USAGE_WRITE, so there must be a good reason.
-	 */
 	panthor_vm_update_resvs(job->group->vm, exec, &sched_job->s_fence->finished,
-				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_WRITE);
+				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);
 }
 
 void panthor_sched_unplug(struct panthor_device *ptdev)
-- 
2.46.0

Re: [PATCH] drm/panthor: Don't add write fences to the shared BOs

[Steven Price]

On 05/09/2024 08:01, Boris Brezillon wrote:
> The only user (the mesa gallium driver) is already assuming explicit
> synchronization and doing the export/import dance on shared BOs. The
> only reason we were registering ourselves as writers on external BOs
> is because Xe, which was the reference back when we developed Panthor,
> was doing so. Turns out Xe was wrong, and we really want bookkeep on
> all registered fences, so userspace can explicitly upgrade those to
> read/write when needed.
> 
> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Simona Vetter <simona.vetter@ffwll.ch>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 9a0ff48f7061..41260cf4beb8 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -3423,13 +3423,8 @@ void panthor_job_update_resvs(struct drm_exec *exec, struct drm_sched_job *sched
>  {
>  	struct panthor_job *job = container_of(sched_job, struct panthor_job, base);
>  
> -	/* Still not sure why we want USAGE_WRITE for external objects, since I
> -	 * was assuming this would be handled through explicit syncs being imported
> -	 * to external BOs with DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but other drivers
> -	 * seem to pass DMA_RESV_USAGE_WRITE, so there must be a good reason.
> -	 */
>  	panthor_vm_update_resvs(job->group->vm, exec, &sched_job->s_fence->finished,
> -				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_WRITE);
> +				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);
>  }
>  
>  void panthor_sched_unplug(struct panthor_device *ptdev)

Re: [PATCH] drm/panthor: Don't add write fences to the shared BOs

[Liviu Dudau]

On Thu, Sep 05, 2024 at 09:01:54AM +0200, Boris Brezillon wrote:
> The only user (the mesa gallium driver) is already assuming explicit
> synchronization and doing the export/import dance on shared BOs. The
> only reason we were registering ourselves as writers on external BOs
> is because Xe, which was the reference back when we developed Panthor,
> was doing so. Turns out Xe was wrong, and we really want bookkeep on
> all registered fences, so userspace can explicitly upgrade those to
> read/write when needed.
> 
> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Simona Vetter <simona.vetter@ffwll.ch>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 9a0ff48f7061..41260cf4beb8 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -3423,13 +3423,8 @@ void panthor_job_update_resvs(struct drm_exec *exec, struct drm_sched_job *sched
>  {
>  	struct panthor_job *job = container_of(sched_job, struct panthor_job, base);
>  
> -	/* Still not sure why we want USAGE_WRITE for external objects, since I
> -	 * was assuming this would be handled through explicit syncs being imported
> -	 * to external BOs with DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but other drivers
> -	 * seem to pass DMA_RESV_USAGE_WRITE, so there must be a good reason.
> -	 */
>  	panthor_vm_update_resvs(job->group->vm, exec, &sched_job->s_fence->finished,
> -				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_WRITE);
> +				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);
>  }
>  
>  void panthor_sched_unplug(struct panthor_device *ptdev)
> -- 
> 2.46.0
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

Re: [PATCH] drm/panthor: Don't add write fences to the shared BOs

[Simona Vetter]

On Thu, Sep 05, 2024 at 09:01:54AM +0200, Boris Brezillon wrote:
> The only user (the mesa gallium driver) is already assuming explicit
> synchronization and doing the export/import dance on shared BOs. The
> only reason we were registering ourselves as writers on external BOs
> is because Xe, which was the reference back when we developed Panthor,
> was doing so. Turns out Xe was wrong, and we really want bookkeep on
> all registered fences, so userspace can explicitly upgrade those to
> read/write when needed.
> 
> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Simona Vetter <simona.vetter@ffwll.ch>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

fwiw Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 9a0ff48f7061..41260cf4beb8 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -3423,13 +3423,8 @@ void panthor_job_update_resvs(struct drm_exec *exec, struct drm_sched_job *sched
>  {
>  	struct panthor_job *job = container_of(sched_job, struct panthor_job, base);
>  
> -	/* Still not sure why we want USAGE_WRITE for external objects, since I
> -	 * was assuming this would be handled through explicit syncs being imported
> -	 * to external BOs with DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but other drivers
> -	 * seem to pass DMA_RESV_USAGE_WRITE, so there must be a good reason.
> -	 */
>  	panthor_vm_update_resvs(job->group->vm, exec, &sched_job->s_fence->finished,
> -				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_WRITE);
> +				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);
>  }
>  
>  void panthor_sched_unplug(struct panthor_device *ptdev)
> -- 
> 2.46.0
> 

-- 
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/panthor: Don't add write fences to the shared BOs

[Boris Brezillon]

On Thu,  5 Sep 2024 09:01:54 +0200
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> The only user (the mesa gallium driver) is already assuming explicit
> synchronization and doing the export/import dance on shared BOs. The
> only reason we were registering ourselves as writers on external BOs
> is because Xe, which was the reference back when we developed Panthor,
> was doing so. Turns out Xe was wrong, and we really want bookkeep on
> all registered fences, so userspace can explicitly upgrade those to
> read/write when needed.
> 
> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Simona Vetter <simona.vetter@ffwll.ch>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Queued to drm-misc-fixes.

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 9a0ff48f7061..41260cf4beb8 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -3423,13 +3423,8 @@ void panthor_job_update_resvs(struct drm_exec *exec, struct drm_sched_job *sched
>  {
>  	struct panthor_job *job = container_of(sched_job, struct panthor_job, base);
>  
> -	/* Still not sure why we want USAGE_WRITE for external objects, since I
> -	 * was assuming this would be handled through explicit syncs being imported
> -	 * to external BOs with DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but other drivers
> -	 * seem to pass DMA_RESV_USAGE_WRITE, so there must be a good reason.
> -	 */
>  	panthor_vm_update_resvs(job->group->vm, exec, &sched_job->s_fence->finished,
> -				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_WRITE);
> +				DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);
>  }
>  
>  void panthor_sched_unplug(struct panthor_device *ptdev)