linux-kernel - Re: [RFC PATCH 1/4] drm/msm: register a fault handler for display mmu faults

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Message-ID: <uywsmpko7ttzqxtlw6i4n5y7zvny5xgdoxc66azbts7cx6vi5d@myrilzxtu7le>
Date: Sun, 19 May 2024 11:38:59 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: freedreno@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, dri-devel@...ts.freedesktop.org, 
	seanpaul@...omium.org, swboyd@...omium.org, dianders@...omium.org, 
	quic_jesszhan@...cinc.com, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] drm/msm: register a fault handler for display
 mmu faults

On Fri, May 17, 2024 at 04:37:56PM -0700, Abhinav Kumar wrote:
> In preparation to register a iommu fault handler for display
> related modules, register a fault handler for the backing
> mmu object of msm_kms.
> 
> Currently, the fault handler only captures the display snapshot
> but we can expand this later if more information needs to be
> added to debug display mmu faults.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> ---
>  drivers/gpu/drm/msm/msm_kms.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/msm_kms.c b/drivers/gpu/drm/msm/msm_kms.c
> index af6a6fcb1173..62c8e6163e81 100644
> --- a/drivers/gpu/drm/msm/msm_kms.c
> +++ b/drivers/gpu/drm/msm/msm_kms.c
> @@ -200,6 +200,28 @@ struct msm_gem_address_space *msm_kms_init_aspace(struct drm_device *dev)
>  	return aspace;
>  }
>  
> +static int msm_kms_fault_handler(void *arg, unsigned long iova, int flags, void *data)
> +{
> +	struct msm_kms *kms = arg;
> +	struct msm_disp_state *state;
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&kms->dump_mutex);
> +	if (ret)
> +		return ret;
> +
> +	state = msm_disp_snapshot_state_sync(kms);
> +
> +	mutex_unlock(&kms->dump_mutex);
> +
> +	if (IS_ERR(state)) {
> +		DRM_DEV_ERROR(kms->dev->dev, "failed to capture snapshot\n");
> +		return PTR_ERR(state);
> +	}
> +
> +	return 0;

Hmm, after reading the rest of the code, this means that we won't get
the error on the console. Could you please change this to -ENOSYS?

> +}
> +
>  void msm_drm_kms_uninit(struct device *dev)
>  {
>  	struct platform_device *pdev = to_platform_device(dev);
> @@ -261,6 +283,9 @@ int msm_drm_kms_init(struct device *dev, const struct drm_driver *drv)
>  		goto err_msm_uninit;
>  	}
>  
> +	if (kms->aspace)
> +		msm_mmu_set_fault_handler(kms->aspace->mmu, kms, msm_kms_fault_handler);
> +
>  	drm_helper_move_panel_connectors_to_head(ddev);
>  
>  	drm_for_each_crtc(crtc, ddev) {
> -- 
> 2.44.0
> 

-- 
With best wishes
Dmitry