linux-kernel - Re: [PATCH] drm/panthor: Enable timestamp propogation

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Message-ID: <61a9daa2-e34a-483e-a577-253feccb65f8@arm.com>
Date: Thu, 20 Nov 2025 16:53:49 +0000
From: Steven Price <steven.price@....com>
To: Ashley Smith <ashley.smith@...labora.com>,
 Boris Brezillon <boris.brezillon@...labora.com>,
 Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panthor: Enable timestamp propogation

On 19/11/2025 16:25, Ashley Smith wrote:
> Set the GLB_COUNTER_EN bit to enable coherent propagation of GPU
> timestamp values to shader cores. This is a prerequisite for exposing
> device-coherent timestamp queries.
>> Bump the version to 1.6 so userspace can detect support.
> 
> Signed-off-by: Ashley Smith <ashley.smith@...labora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_drv.c | 3 ++-
>  drivers/gpu/drm/panthor/panthor_fw.c  | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index d1d4c50da5bf..0b0ec3b978c6 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1604,6 +1604,7 @@ static void panthor_debugfs_init(struct drm_minor *minor)
>   * - 1.3 - adds DRM_PANTHOR_GROUP_STATE_INNOCENT flag
>   * - 1.4 - adds DRM_IOCTL_PANTHOR_BO_SET_LABEL ioctl
>   * - 1.5 - adds DRM_PANTHOR_SET_USER_MMIO_OFFSET ioctl
> + * - 1.6 - enables GLB_COUNTER_EN
>   */
>  static const struct drm_driver panthor_drm_driver = {
>  	.driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ |
> @@ -1617,7 +1618,7 @@ static const struct drm_driver panthor_drm_driver = {
>  	.name = "panthor",
>  	.desc = "Panthor DRM driver",
>  	.major = 1,
> -	.minor = 5,
> +	.minor = 6,
>  
>  	.gem_create_object = panthor_gem_create_object,
>  	.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table,
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index 38d87ab92eda..a02fb3afc2e1 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -999,6 +999,7 @@ static void panthor_fw_init_global_iface(struct panthor_device *ptdev)
>  	panthor_fw_update_reqs(glb_iface, req, GLB_IDLE_EN, GLB_IDLE_EN);
>  	panthor_fw_toggle_reqs(glb_iface, req, ack,
>  			       GLB_CFG_ALLOC_EN |
> +			       GLB_COUNTER_EN |
>  			       GLB_CFG_POWEROFF_TIMER |
>  			       GLB_CFG_PROGRESS_TIMER);

This is definitely the wrong function. The COUNTER_ENABLE field isn't a
toggle field. So '1' enables the counter propagation, '0' disables it.
This code is toggling it so changing it from whatever default it started
out at.

Testing on my Rock5B I see that it does seem to start at 0, so this is
probably why it seemed to work. But you need to include this value in
the panthor_fw_update_reqs() call instead.

Thanks,
Steve

>  
> 
> base-commit: 92c49b3f4df8f9acfa95551ef38fc00c675319fd