Re: [PATCH v2 1/6] drm/msm/dpu: reset unassigned resource slots to NULL on topology update

[Val Packett]

On 10/26/26 5:25 PM, Xi Zhang wrote:
> While this is not currently the case, it may be possible that topology
> for cwb and dsc resource requirements change between mode set in the
> future.
>
> e.g. when dsc support is added to DisplayPort, dsc may be optionally
> enabled and disabled between different modes due to
> bandwidth requirements.
>
> Set unassigned resource slots to NULL on topology update to avoid
> issues in the future. It's good practice to do so anyway.
>
> Signed-off-by: Xi Zhang <xz.ca.cn@xxxxxxxxx>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 22 +++++++++++++++-------
>   1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 0a6be69a3e83..8d2b4d2726f2 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -1205,9 +1205,13 @@ static void dpu_encoder_virt_atomic_mode_set(struct drm_encoder *drm_enc,
>   						       ARRAY_SIZE(hw_pp));
>   	}
>   
> -	for (i = 0; i < num_cwb; i++) {
> -		dpu_enc->hw_cwb[i] = to_dpu_hw_cwb(hw_cwb[i]);
> -		cwb_mask |= BIT(dpu_enc->hw_cwb[i]->idx - CWB_0);
> +	for (i = 0; i < ARRAY_SIZE(dpu_enc->hw_cwb); i++) {
> +		if (i < num_cwb) {
> +			dpu_enc->hw_cwb[i] = to_dpu_hw_cwb(hw_cwb[i]);
> +			cwb_mask |= BIT(dpu_enc->hw_cwb[i]->idx - CWB_0);
> +		} else {
> +			dpu_enc->hw_cwb[i] = NULL;
> +		}
> [..]

I've mentioned in a reply to v1 that this was indeed affected by the DSC 
changes in radxa's WIP, but missed the more relevant one:

This is already handled by the "drm/msm: fix SMMU fault dumps" series:

https://lore.kernel.org/all/20261024-fd-kms-fix-smmu-v5-0-a5b0b284aead@xxxxxxxxxxxxxxxx/

Namely patches 5-8 ("drm/msm/dpu: clear the ... blocks ...")

Thanks,
~val