linux-kernel - Re: [PATCH v5 06/15] drm/msm/dpu: fix mixer number counter on allocation

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Message-ID: <18840118-243c-40e2-9b74-226e515ae111@quicinc.com>
Date: Fri, 14 Feb 2025 16:48:47 -0800
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Jun Nie <jun.nie@...aro.org>, Rob Clark <robdclark@...il.com>,
        "Abhinav
 Kumar" <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 06/15] drm/msm/dpu: fix mixer number counter on
 allocation



On 1/17/2025 8:00 AM, Jun Nie wrote:
> Current code only supports usage cases with one pair of mixers at
> most. To support quad-pipe usage case, two pairs of mixers need to
> be reserved. The lm_count for all pairs is cleared if a peer
> allocation fails in current implementation. Reset the current lm_count
> to an even number instead of completely clearing it. This prevents all
> pairs from being cleared in cases where multiple LM pairs are needed.
> 
> Signed-off-by: Jun Nie <jun.nie@...aro.org>

Reviewed-by: Jessica Zhang <quic_jesszhan@...cinc.com>

> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index 24e085437039e..3b3660d0b166d 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -321,7 +321,11 @@ static int _dpu_rm_reserve_lms(struct dpu_rm *rm,
>   		if (!rm->mixer_blks[i])
>   			continue;
>   
> -		lm_count = 0;
> +		/*
> +		 * Reset lm_count to an even index. This will drop the previous
> +		 * primary mixer if failed to find its peer.
> +		 */
> +		lm_count &= ~1;
>   		lm_idx[lm_count] = i;
>   
>   		if (!_dpu_rm_check_lm_and_get_connected_blks(rm, global_state,
> 
> -- 
> 2.34.1
>