linux-kernel - Re: [PATCH 5/7] drm/msm/A6xx: Add traces for preemption

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Message-ID: <20240819201123.6eeahdbf5ezaloof@hu-akhilpo-hyd.qualcomm.com>
Date: Tue, 20 Aug 2024 01:41:23 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Antonino Maniscalco <antomani103@...il.com>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "Konrad
 Dybcio" <konrad.dybcio@...aro.org>,
        Abhinav Kumar
	<quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie
	<airlied@...il.com>, "Daniel Vetter" <daniel@...ll.ch>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7] drm/msm/A6xx: Add traces for preemption

On Thu, Aug 15, 2024 at 08:26:15PM +0200, Antonino Maniscalco wrote:
> Add trace points corresponding to preemption being triggered and being
> completed for latency measurement purposes.
> 
> Signed-off-by: Antonino Maniscalco <antomani103@...il.com>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_preempt.c |  7 +++++++
>  drivers/gpu/drm/msm/msm_gpu_trace.h       | 28 ++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> index 0d402a3bcf5a..2606835f3c6d 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> @@ -7,6 +7,7 @@
>  #include "a6xx_gpu.h"
>  #include "a6xx_gmu.xml.h"
>  #include "msm_mmu.h"
> +#include "msm_gpu_trace.h"
>  
>  #define FENCE_STATUS_WRITEDROPPED0_MASK 0x1
>  #define FENCE_STATUS_WRITEDROPPED1_MASK 0x2

These seems unused in this file. I think the previous patch added this.

> @@ -146,6 +147,8 @@ void a6xx_preempt_irq(struct msm_gpu *gpu)
>  
>  	set_preempt_state(a6xx_gpu, PREEMPT_NONE);
>  
> +	trace_msm_gpu_preemption_irq(a6xx_gpu->cur_ring->id);
> +
>  	/*
>  	 * Retrigger preemption to avoid a deadlock that might occur when preemption
>  	 * is skipped due to it being already in flight when requested.
> @@ -262,6 +265,10 @@ void a6xx_preempt_trigger(struct msm_gpu *gpu)
>  	 */
>  	ring->skip_inline_wptr = false;
>  
> +	trace_msm_gpu_preemption_trigger(
> +		a6xx_gpu->cur_ring ? a6xx_gpu->cur_ring->id : -1,

Can't we avoid this check? I mean GPU has initialized on one of the
RBs at this point.

-Akhil.

> +		ring ? ring->id : -1);
> +
>  	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	gpu_write64(gpu,
> diff --git a/drivers/gpu/drm/msm/msm_gpu_trace.h b/drivers/gpu/drm/msm/msm_gpu_trace.h
> index ac40d857bc45..7f863282db0d 100644
> --- a/drivers/gpu/drm/msm/msm_gpu_trace.h
> +++ b/drivers/gpu/drm/msm/msm_gpu_trace.h
> @@ -177,6 +177,34 @@ TRACE_EVENT(msm_gpu_resume,
>  		TP_printk("%u", __entry->dummy)
>  );
>  
> +TRACE_EVENT(msm_gpu_preemption_trigger,
> +		TP_PROTO(int ring_id_from, int ring_id_to),
> +		TP_ARGS(ring_id_from, ring_id_to),
> +		TP_STRUCT__entry(
> +			__field(int, ring_id_from)
> +			__field(int, ring_id_to)
> +			),
> +		TP_fast_assign(
> +			__entry->ring_id_from = ring_id_from;
> +			__entry->ring_id_to = ring_id_to;
> +			),
> +		TP_printk("preempting %u -> %u",
> +			  __entry->ring_id_from,
> +			  __entry->ring_id_to)
> +);
> +
> +TRACE_EVENT(msm_gpu_preemption_irq,
> +		TP_PROTO(u32 ring_id),
> +		TP_ARGS(ring_id),
> +		TP_STRUCT__entry(
> +			__field(u32, ring_id)
> +			),
> +		TP_fast_assign(
> +			__entry->ring_id = ring_id;
> +			),
> +		TP_printk("preempted to %u", __entry->ring_id)
> +);
> +
>  #endif
>  
>  #undef TRACE_INCLUDE_PATH
> 
> -- 
> 2.46.0
> 
>