linux-kernel - Re: [PATCH 2/2] media: vsp1: vsp1

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Message-ID: <qypirqm25w3k62j27bk7hmyxpcsompygiaey2fzwp2z7y3t6sf@uncpux7arh4n>
Date: Mon, 16 Jun 2025 16:35:13 +0200
From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Jacopo Mondi <jacopo.mondi+renesas@...asonboard.com>, 
	Kieran Bingham <kieran.bingham+renesas@...asonboard.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] media: vsp1: vsp1_dl: Count display lists

Hi Laurent

On Mon, Jun 16, 2025 at 04:31:34PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Thu, May 29, 2025 at 06:36:31PM +0200, Jacopo Mondi wrote:
> > To detect invalid usage patterns of the display list helpers, store
>
> We can be more precise:
>
> "To detect leaks of display lists, ..."
>
> > in the display list manager the number of available display lists
>
> s/available/allocated/
>
> > when the manager is created and verify that when the display manager
> > is reset the same number of lists is available.
> >
> > Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@...asonboard.com>
> > ---
> >  drivers/media/platform/renesas/vsp1/vsp1_dl.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/media/platform/renesas/vsp1/vsp1_dl.c b/drivers/media/platform/renesas/vsp1/vsp1_dl.c
> > index 8a3c0274a163..5c4eeb65216f 100644
> > --- a/drivers/media/platform/renesas/vsp1/vsp1_dl.c
> > +++ b/drivers/media/platform/renesas/vsp1/vsp1_dl.c
> > @@ -214,6 +214,7 @@ struct vsp1_dl_list {
> >   * @pending: list waiting to be queued to the hardware
> >   * @pool: body pool for the display list bodies
> >   * @cmdpool: commands pool for extended display list
> > + * @list_count: display list counter
>
> "number of allocated display lists"
>
> >   */
> >  struct vsp1_dl_manager {
> >  	unsigned int index;
> > @@ -228,6 +229,8 @@ struct vsp1_dl_manager {
> >
> >  	struct vsp1_dl_body_pool *pool;
> >  	struct vsp1_dl_cmd_pool *cmdpool;
> > +
> > +	size_t list_count;
> >  };
> >
> >  /* -----------------------------------------------------------------------------
> > @@ -1073,7 +1076,9 @@ void vsp1_dlm_setup(struct vsp1_device *vsp1)
> >
> >  void vsp1_dlm_reset(struct vsp1_dl_manager *dlm)
> >  {
> > +	size_t dlm_list_count;
> >  	unsigned long flags;
> > +	size_t list_count;
> >
> >  	spin_lock_irqsave(&dlm->lock, flags);
> >
> > @@ -1081,8 +1086,13 @@ void vsp1_dlm_reset(struct vsp1_dl_manager *dlm)
> >  	__vsp1_dl_list_put(dlm->queued);
> >  	__vsp1_dl_list_put(dlm->pending);
> >
> > +	list_count = list_count_nodes(&dlm->free);
> > +	dlm_list_count = dlm->list_count;
>
> dlm->list_count is not documented as protected by the lock. I don't
> think that's an oversight, as it can only be set when the dlm is
> created. You can drop the dlm_list_count variable and use
> dlm->list_count below.
>
Ack

> > +
> >  	spin_unlock_irqrestore(&dlm->lock, flags);
> >
> > +	WARN_ON_ONCE(list_count != dlm_list_count);
> > +
> >  	dlm->active = NULL;
> >  	dlm->queued = NULL;
> >  	dlm->pending = NULL;
> > @@ -1150,6 +1160,7 @@ struct vsp1_dl_manager *vsp1_dlm_create(struct vsp1_device *vsp1,
> >  				      + sizeof(*dl->header);
> >
> >  		list_add_tail(&dl->list, &dlm->free);
> > +		dlm->list_count = list_count_nodes(&dlm->free);
>
> Does this need to be done inside the loop, can't you just write
>
> 	dlm->list_count = prealloc;
>
> after the loop ?
>

Oh indeed, this was stupid. Thanks for catching this

> >  	}
> >
> >  	if (vsp1_feature(vsp1, VSP1_HAS_EXT_DL)) {
>
> --
> Regards,
>
> Laurent Pinchart