Re: [PATCH 07/11] drm/i915/skl+: Fail the flip if ddb min requirement exceeds pipe allocation

[Ander Conselvan De Oliveira <conselvan2@gmail.com>]

On Mon, 2017-05-08 at 17:18 +0530, Mahesh Kumar wrote:
> DDB minimum requirement may exceed the allocated DDB for CRTC/Pipe. This
> patch make changes to fail the flip 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 later calculations for plane ddb allocation bogus & may lead
> to screen corruption or system hang.

When sending a new version of a patch, please list the changes from the previous
version here. For example:

v2: Improve commit message.

v3: ...

> Signed-off-by: Mahesh Kumar <mahesh1.kumar@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 2a4e9d89cd6f..0ace94d67432 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3591,6 +3591,7 @@ 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]));
> @@ -3618,10 +3619,18 @@ 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;
> +	}

The comments I made earlier [1] are still valid. With those fixed and a
changelog in the commit message,

Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>

[1] https://lists.freedesktop.org/archives/intel-gfx/2017-April/125764.html
> +
> +	alloc_size -= total_min_blocks;
>  	ddb->plane[pipe][PLANE_CURSOR].start = alloc->end - minimum[PLANE_CURSOR];
>  	ddb->plane[pipe][PLANE_CURSOR].end = alloc->end;
>  
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