[Intel-gfx] [PATCH 07/12] drm/i915/skl+: Fail the flip if ddb min requirement exceeds pipe allocation

[Matt Roper]

On Mon, May 15, 2017 at 02:04:32PM +0530, Mahesh Kumar wrote:
> From: "Kumar, Mahesh" <mahesh1.kumar at intel.com>
> 
> DDB minimum requirement of crtc configuration (cumulative of all the
> enabled planes in crtc) may exceed the allocated DDB for crtc/pipe.
> This patch make changes to fail the flip/ioctl if minimum requirement
> for pipe exceeds the total ddb allocated to the pipe.
> Previously it succeeded but making alloc_size a negative value. Which
> will make subsequent calculations for plane ddb allocation bogus & may
> lead to screen corruption or system hang.
> 
> Changes from V1:
>  - Improve commit message as per Ander's comment
>  - Remove extra parentheses (Ander)
> 
> Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 37dd3e7108c9..bbc72069ab57 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4057,6 +4057,7 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>  	int num_active;
>  	unsigned plane_data_rate[I915_MAX_PLANES] = {};
>  	unsigned plane_y_data_rate[I915_MAX_PLANES] = {};
> +	uint16_t total_min_blocks = 0;
>  
>  	/* Clear the partitioning for disabled planes. */
>  	memset(ddb->plane[pipe], 0, sizeof(ddb->plane[pipe]));
> @@ -4084,10 +4085,18 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>  	 */
>  
>  	for_each_plane_id_on_crtc(intel_crtc, plane_id) {
> -		alloc_size -= minimum[plane_id];
> -		alloc_size -= y_minimum[plane_id];
> +		total_min_blocks += minimum[plane_id];
> +		total_min_blocks += y_minimum[plane_id];
>  	}
>  
> +	if (total_min_blocks > alloc_size) {
> +		DRM_DEBUG_KMS("Requested display configuration exceeds system DDB limitations");
> +		DRM_DEBUG_KMS("minimum required %d/%d\n", total_min_blocks,
> +							alloc_size);
> +		return -EINVAL;
> +	}
> +
> +	alloc_size -= total_min_blocks;
>  	ddb->plane[pipe][PLANE_CURSOR].start = alloc->end - minimum[PLANE_CURSOR];
>  	ddb->plane[pipe][PLANE_CURSOR].end = alloc->end;
>  
> -- 
> 2.11.0
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795