Re: [PATCH v7 1/6] drm/panthor: Expose GPU page sizes to UM

[Boris Brezillon <boris.brezillon@collabora.com>]

On Wed, 15 Apr 2026 12:28:45 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> In future commits that will implement repeated mappings, only repeat
> values multiple of GPU page sizes will be tolerated. That means these
> values must be made known to UM. Do it through a queriable GPU info
> value.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/panthor/panthor_device.h |  3 +++
>  drivers/gpu/drm/panthor/panthor_drv.c    |  8 ++++++++
>  drivers/gpu/drm/panthor/panthor_mmu.c    |  9 ++++++++-
>  include/uapi/drm/panthor_drm.h           | 13 +++++++++++++
>  4 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 5cba272f9b4d..d856a4fe1d61 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -158,6 +158,9 @@ struct panthor_device {
>  	/** @csif_info: Command stream interface information. */
>  	struct drm_panthor_csif_info csif_info;
>  
> +	/** @mmu_info: MMU info */
> +	struct drm_panthor_mmu_info mmu_info;
> +
>  	/** @hw: GPU-specific data. */
>  	struct panthor_hw *hw;
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index 73fc983dc9b4..a8090bc4e33c 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -175,6 +175,7 @@ panthor_get_uobj_array(const struct drm_panthor_obj_array *in, u32 min_stride,
>  	_Generic(_obj_name, \
>  		 PANTHOR_UOBJ_DECL(struct drm_panthor_gpu_info, tiler_present), \
>  		 PANTHOR_UOBJ_DECL(struct drm_panthor_csif_info, pad), \
> +		 PANTHOR_UOBJ_DECL(struct drm_panthor_mmu_info, page_size_bitmap), \
>  		 PANTHOR_UOBJ_DECL(struct drm_panthor_timestamp_info, current_timestamp), \
>  		 PANTHOR_UOBJ_DECL(struct drm_panthor_group_priorities_info, pad), \
>  		 PANTHOR_UOBJ_DECL(struct drm_panthor_sync_op, timeline_value), \
> @@ -946,6 +947,10 @@ static int panthor_ioctl_dev_query(struct drm_device *ddev, void *data, struct d
>  			args->size = sizeof(ptdev->csif_info);
>  			return 0;
>  
> +		case DRM_PANTHOR_DEV_QUERY_MMU_INFO:
> +			args->size = sizeof(ptdev->mmu_info);
> +			return 0;
> +
>  		case DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO:
>  			args->size = sizeof(timestamp_info);
>  			return 0;
> @@ -966,6 +971,9 @@ static int panthor_ioctl_dev_query(struct drm_device *ddev, void *data, struct d
>  	case DRM_PANTHOR_DEV_QUERY_CSIF_INFO:
>  		return PANTHOR_UOBJ_SET(args->pointer, args->size, ptdev->csif_info);
>  
> +	case DRM_PANTHOR_DEV_QUERY_MMU_INFO:
> +		return PANTHOR_UOBJ_SET(args->pointer, args->size, ptdev->mmu_info);
> +
>  	case DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO:
>  		ret = copy_struct_from_user(&timestamp_info,
>  					    sizeof(timestamp_info),
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index bd41c892beb7..01577be88933 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -2769,7 +2769,7 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
>  	refcount_set(&vm->as.active_cnt, 0);
>  
>  	pgtbl_cfg = (struct io_pgtable_cfg) {
> -		.pgsize_bitmap	= SZ_4K | SZ_2M,
> +		.pgsize_bitmap	= ptdev->mmu_info.page_size_bitmap,
>  		.ias		= va_bits,
>  		.oas		= pa_bits,
>  		.coherent_walk	= ptdev->coherent,
> @@ -3214,6 +3214,11 @@ static void panthor_mmu_release_wq(struct drm_device *ddev, void *res)
>  	destroy_workqueue(res);
>  }
>  
> +static void panthor_mmu_info_init(struct panthor_device *ptdev)
> +{
> +	ptdev->mmu_info.page_size_bitmap = SZ_4K | SZ_2M;
> +}
> +
>  /**
>   * panthor_mmu_init() - Initialize the MMU logic.
>   * @ptdev: Device.
> @@ -3226,6 +3231,8 @@ int panthor_mmu_init(struct panthor_device *ptdev)
>  	struct panthor_mmu *mmu;
>  	int ret, irq;
>  
> +	panthor_mmu_info_init(ptdev);
> +
>  	mmu = drmm_kzalloc(&ptdev->base, sizeof(*mmu), GFP_KERNEL);
>  	if (!mmu)
>  		return -ENOMEM;
> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
> index 0e455d91e77d..dc2704fc2829 100644
> --- a/include/uapi/drm/panthor_drm.h
> +++ b/include/uapi/drm/panthor_drm.h
> @@ -246,6 +246,9 @@ enum drm_panthor_dev_query_type {
>  	/** @DRM_PANTHOR_DEV_QUERY_CSIF_INFO: Query command-stream interface information. */
>  	DRM_PANTHOR_DEV_QUERY_CSIF_INFO,
>  
> +	/** @DRM_PANTHOR_DEV_QUERY_MMU_INFO: Query MMU information. */
> +	DRM_PANTHOR_DEV_QUERY_MMU_INFO,
> +
>  	/** @DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO: Query timestamp information. */
>  	DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO,
>  
> @@ -487,6 +490,16 @@ struct drm_panthor_timestamp_info {
>  	__u64 cpu_timestamp_nsec;
>  };
>  
> +/**
> + * struct drm_panthor_mmu_info - MMU information
> + *
> + * Structure grouping all queryable information relating to the MMU.
> + */
> +struct drm_panthor_mmu_info {
> +	/** @page_size_bitmap: Allowed page sizes */

Maybe add more info there: like, page size is a power of two, and each
bit encodes a particular page size.

> +	__u64 page_size_bitmap;
> +};
> +
>  /**
>   * struct drm_panthor_group_priorities_info - Group priorities information
>   *