Re: [PATCH 2/2] drm/imagination: Fix page count for page table for map() interface

[Alessio Belle <Alessio.Belle@imgtec.com>]

Hi Brajesh,

On Wed, 2026-09-02 at 15:25 +0530, Brajesh Gupta wrote:
> GPU virtual start address wasn't included in page count for page table
> calculation for mapping an BO object in map() interface. It resulted in

Maybe the other way round could be slightly clearer? e.g. "The GPU virtual start
address wasn't included in the calculation for the amount of page tables
required for mapping a BO object.".

> map failure later due to not enough pages at L0/L1 level.
> Update pvr_mmu_op_context_create() interface to pass device address as well
> to allow correct calculation for page table memory.
> 
> Miscalculation of page table pages for mapping a BO starting at a device
> address 0x8001b45000 of size 0x8ca000:
>                old       new
> L0 count       5          6
> L1 count       1          1
> 
> Fixes: ff5f643de0bf ("drm/imagination: Add GEM and VM related code")

I'd add the stable tag to this one as well.

> Signed-off-by: Brajesh Gupta <brajesh.gupta@imgtec.com>
> ---
>  drivers/gpu/drm/imagination/pvr_mmu.c | 14 ++++++++------
>  drivers/gpu/drm/imagination/pvr_mmu.h |  2 +-
>  drivers/gpu/drm/imagination/pvr_vm.c  |  4 ++--
>  3 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_mmu.c b/drivers/gpu/drm/imagination/pvr_mmu.c
> index 175f0ba4d993..52d8fbc00384 100644
> --- a/drivers/gpu/drm/imagination/pvr_mmu.c
> +++ b/drivers/gpu/drm/imagination/pvr_mmu.c
> @@ -2336,6 +2336,7 @@ void pvr_mmu_op_context_destroy(struct pvr_mmu_op_context *op_ctx)
>   * pvr_mmu_op_context_create() - Create an MMU op context.
>   * @ctx: MMU context associated with owning VM context.
>   * @sgt: Scatter gather table containing pages pinned for use by this context.
> + * @device_add: Virtual device address at the start of the requested mapping.

Typo device_add -> device_addr.

With these updated:

Reviewed-by: Alessio Belle <alessio.belle@imgtec.com>

Thanks,
Alessio

>   * @sgt_offset: Start offset of the requested device-virtual memory mapping.
>   * @size: Size in bytes of the requested device-virtual memory mapping. For an
>   * unmapping, this should be zero so that no page tables are allocated.
> @@ -2347,8 +2348,9 @@ void pvr_mmu_op_context_destroy(struct pvr_mmu_op_context *op_ctx)
>   */
>  struct pvr_mmu_op_context *
>  pvr_mmu_op_context_create(struct pvr_mmu_context *ctx, struct sg_table *sgt,
> -			  u64 sgt_offset, u64 size)
> +			  u64 device_addr, u64 sgt_offset, u64 size)
>  {
> +	u64 start_addr = device_addr + sgt_offset;
>  	int err;
>  
>  	struct pvr_mmu_op_context *op_ctx = kzalloc_obj(*op_ctx);
> @@ -2364,16 +2366,16 @@ pvr_mmu_op_context_create(struct pvr_mmu_context *ctx, struct sg_table *sgt,
>  	if (size) {
>  		/*
>  		 * The number of page table objects we need to prealloc is
> -		 * indicated by the mapping size, start offset and the sizes
> +		 * indicated by the mapping size, start address and the sizes
>  		 * of the areas mapped per PT or PD. The range calculation is
>  		 * identical to that for the index into a table for a device
>  		 * address, so we reuse those functions here.
>  		 */
> -		const u32 l1_start_idx = pvr_page_table_l2_idx(sgt_offset);
> -		const u32 l1_end_idx = pvr_page_table_l2_idx(sgt_offset + size);
> +		const u32 l1_start_idx = pvr_page_table_l2_idx(start_addr);
> +		const u32 l1_end_idx = pvr_page_table_l2_idx(start_addr + size);
>  		const u32 l1_count = l1_end_idx - l1_start_idx + 1;
> -		const u32 l0_start_idx = pvr_page_table_l1_idx(sgt_offset);
> -		const u32 l0_end_idx = pvr_page_table_l1_idx(sgt_offset + size);
> +		const u32 l0_start_idx = pvr_page_table_l1_idx(start_addr);
> +		const u32 l0_end_idx = pvr_page_table_l1_idx(start_addr + size);
>  		const u32 l0_count = l0_end_idx - l0_start_idx + 1;
>  
>  		/*
> diff --git a/drivers/gpu/drm/imagination/pvr_mmu.h b/drivers/gpu/drm/imagination/pvr_mmu.h
> index a8ecd460168d..2c02d61ba0a2 100644
> --- a/drivers/gpu/drm/imagination/pvr_mmu.h
> +++ b/drivers/gpu/drm/imagination/pvr_mmu.h
> @@ -99,7 +99,7 @@ dma_addr_t pvr_mmu_get_root_table_dma_addr(struct pvr_mmu_context *ctx);
>  void pvr_mmu_op_context_destroy(struct pvr_mmu_op_context *op_ctx);
>  struct pvr_mmu_op_context *
>  pvr_mmu_op_context_create(struct pvr_mmu_context *ctx,
> -			  struct sg_table *sgt, u64 sgt_offset, u64 size);
> +			  struct sg_table *sgt, u64 device_addr, u64 sgt_offset, u64 size);
>  
>  int pvr_mmu_map(struct pvr_mmu_op_context *op_ctx, u64 size, u64 flags,
>  		u64 device_addr);
> diff --git a/drivers/gpu/drm/imagination/pvr_vm.c b/drivers/gpu/drm/imagination/pvr_vm.c
> index 396d349fb6ce..867a4a44958a 100644
> --- a/drivers/gpu/drm/imagination/pvr_vm.c
> +++ b/drivers/gpu/drm/imagination/pvr_vm.c
> @@ -276,7 +276,7 @@ pvr_vm_bind_op_map_init(struct pvr_vm_bind_op *bind_op,
>  		goto err_bind_op_fini;
>  
>  	bind_op->mmu_op_ctx =
> -		pvr_mmu_op_context_create(vm_ctx->mmu_ctx, sgt, offset, size);
> +		pvr_mmu_op_context_create(vm_ctx->mmu_ctx, sgt, device_addr, offset, size);
>  	err = PTR_ERR_OR_ZERO(bind_op->mmu_op_ctx);
>  	if (err) {
>  		bind_op->mmu_op_ctx = NULL;
> @@ -318,7 +318,7 @@ pvr_vm_bind_op_unmap_init(struct pvr_vm_bind_op *bind_op,
>  	}
>  
>  	bind_op->mmu_op_ctx =
> -		pvr_mmu_op_context_create(vm_ctx->mmu_ctx, NULL, 0, 0);
> +		pvr_mmu_op_context_create(vm_ctx->mmu_ctx, NULL, device_addr, 0, 0);
>  	err = PTR_ERR_OR_ZERO(bind_op->mmu_op_ctx);
>  	if (err) {
>  		bind_op->mmu_op_ctx = NULL;
>