linux-kernel - Re: [Freedreno] [PATCH 1/2] drm/msm: Add a GPU-wide wait queue

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Message-ID: <20200113175522.GD26711@jcrouse1-lnx.qualcomm.com>
Date:   Mon, 13 Jan 2020 10:55:22 -0700
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Brian Ho <brian@...ho.com>
Cc:     freedreno@...ts.freedesktop.org, robdclark@...omium.org,
        David Airlie <airlied@...ux.ie>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <dri-devel@...ts.freedesktop.org>, Rob Clark <robdclark@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, hoegsberg@...omium.org,
        Sean Paul <sean@...rly.run>
Subject: Re: [Freedreno] [PATCH 1/2] drm/msm: Add a GPU-wide wait queue

On Mon, Jan 13, 2020 at 10:36:04AM -0500, Brian Ho wrote:
> This wait queue is signaled on all IRQs for a given GPU and will be
> used as part of the new MSM_WAIT_IOVA ioctl so userspace can sleep
> until the value at a given iova reaches a certain condition.
> 
> Signed-off-by: Brian Ho <brian@...ho.com>
> ---
>  drivers/gpu/drm/msm/msm_gpu.c | 4 ++++
>  drivers/gpu/drm/msm/msm_gpu.h | 3 +++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index a052364a5d74..d7310c1336e5 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -779,6 +779,8 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit,
>  static irqreturn_t irq_handler(int irq, void *data)
>  {
>  	struct msm_gpu *gpu = data;
> +	wake_up_all(&gpu->event);
> +

I suppose it is intentional to have this happen on *all* interrupts because you
might be using the CP interrupts for fun and profit and you don't want to plumb
in callbacks?  I suppose it is okay to do this for all interrupts (including
errors) but if we're spending a lot of time here we might want to only trigger
on certain IRQs.

>  	return gpu->funcs->irq(gpu);
>  }
>  
> @@ -871,6 +873,8 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>  
>  	spin_lock_init(&gpu->perf_lock);
>  
> +	init_waitqueue_head(&gpu->event);
> +
>  
>  	/* Map registers: */
>  	gpu->mmio = msm_ioremap(pdev, config->ioname, name);
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index ab8f0f9c9dc8..60562f065dbc 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -104,6 +104,9 @@ struct msm_gpu {
>  
>  	struct msm_gem_address_space *aspace;
>  
> +	/* GPU-wide wait queue that is signaled on all IRQs */
> +	wait_queue_head_t event;
> +
>  	/* Power Control: */
>  	struct regulator *gpu_reg, *gpu_cx;
>  	struct clk_bulk_data *grp_clks;
> -- 
> 2.25.0.rc1.283.g88dfdc4193-goog
> 
> _______________________________________________
> Freedreno mailing list
> Freedreno@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/freedreno

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