linux-kernel - Re: [PATCH] drm/panthor: always set fence errors on CS

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Message-ID: <20250623083241.02127feb@fedora>
Date: Mon, 23 Jun 2025 08:32:41 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Chia-I Wu <olvaffe@...il.com>
Cc: Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panthor: always set fence errors on CS_FAULT

On Wed, 18 Jun 2025 07:55:49 -0700
Chia-I Wu <olvaffe@...il.com> wrote:

> It is unclear why fence errors were set only for CS_INHERIT_FAULT.
> Downstream driver also does not treat CS_INHERIT_FAULT specially.
> Remove the check.
> 
> Signed-off-by: Chia-I Wu <olvaffe@...il.com>
> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index a2248f692a030..1a3b1c49f7d7b 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -1399,7 +1399,7 @@ cs_slot_process_fault_event_locked(struct panthor_device *ptdev,
>  	fault = cs_iface->output->fault;
>  	info = cs_iface->output->fault_info;
>  
> -	if (queue && CS_EXCEPTION_TYPE(fault) == DRM_PANTHOR_EXCEPTION_CS_INHERIT_FAULT) {
> +	if (queue) {
>  		u64 cs_extract = queue->iface.output->extract;
>  		struct panthor_job *job;
>  

Now that I look at the code, I think we should record the error when
the ERROR_BARRIER is executed instead of flagging all in-flight jobs as
faulty. One option would be to re-use the profiling buffer by adding an
error field to panthor_job_profiling_data, but we're going to lose 4
bytes per slot because of the 64-bit alignment we want for timestamps,
so maybe just create a separate buffers with N entries of:

struct panthor_job_status {
   u32 error;
};