linux-kernel - Re: [PATCH v7 4/5] media: platform: mediatek: isp: add mediatek ISP3.0 camsv

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Message-ID: <CAEHHSvbFw+MC0R3w7isgrF15JAAfBWQmSkh1PoiU7y+P4O2psw@mail.gmail.com>
Date: Fri, 22 Nov 2024 10:44:52 +0100
From: Julien Stephan <jstephan@...libre.com>
To: CK Hu (胡俊光) <ck.hu@...iatek.com>
Cc: "mchehab@...nel.org" <mchehab@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>, 
	"robh@...nel.org" <robh@...nel.org>, Andy Hsieh (謝智皓) <Andy.Hsieh@...iatek.com>, 
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>, 
	"laurent.pinchart@...asonboard.com" <laurent.pinchart@...asonboard.com>, 
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>, 
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"paul.elder@...asonboard.com" <paul.elder@...asonboard.com>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	"fsylvestre@...libre.com" <fsylvestre@...libre.com>, "pnguyen@...libre.com" <pnguyen@...libre.com>
Subject: Re: [PATCH v7 4/5] media: platform: mediatek: isp: add mediatek
 ISP3.0 camsv

Le ven. 22 nov. 2024 à 10:19, CK Hu (胡俊光) <ck.hu@...iatek.com> a écrit :
>
> Hi, Julien:
>
> On Thu, 2024-11-21 at 09:53 +0100, Julien Stephan wrote:
> > External email : Please do not click links or open attachments until you have verified the sender or the content.
> >
> >
> > From: Phi-bang Nguyen <pnguyen@...libre.com>
> >
> > This driver provides a path to bypass the SoC ISP so that image data
> > coming from the SENINF can go directly into memory without any image
> > processing. This allows the use of an external ISP.
> >
> > Signed-off-by: Phi-bang Nguyen <pnguyen@...libre.com>
> > Signed-off-by: Florian Sylvestre <fsylvestre@...libre.com>
> > [Paul Elder fix irq locking]
> > Signed-off-by: Paul Elder <paul.elder@...asonboard.com>
> > Co-developed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > Co-developed-by: Julien Stephan <jstephan@...libre.com>
> > Signed-off-by: Julien Stephan <jstephan@...libre.com>
> > ---
>
> [snip]
>
> > +static void mtk_cam_vb2_buf_queue(struct vb2_buffer *vb)
> > +{
> > +       struct mtk_cam_dev *cam = vb2_get_drv_priv(vb->vb2_queue);
> > +       struct mtk_cam_dev_buffer *buf = to_mtk_cam_dev_buffer(vb);
> > +       unsigned long flags;
> > +
> > +       /* Add the buffer into the tracking list */
> > +       spin_lock_irqsave(&cam->buf_list_lock, flags);
> > +       if (list_empty(&cam->buf_list))
> > +               (*cam->hw_functions->mtk_cam_update_buffers_add)(cam, buf);
> > +
> > +       list_add_tail(&buf->list, &cam->buf_list);
> > +       (*cam->hw_functions->mtk_cam_fbc_inc)(cam);
>
> I think fbc_inc should together with update_buffers_add.
> After update_buffers_add then fbc_inc.
> So squash fbc_inc into update_buffers_add and drop fbc_inc function.
>

No, this is not true.
mtk_cam_update_buffers_add is used to indicate which buffer should be
used for dma write. This is the first entry in the buf list.
mtk_cam_fbc_inc is used to increase the number of available user space buffers.

If the buffer list is not empty and user space calls buf_queue again,
we need to call mtk_cam_fbc_inc to increase the number of available
user buffers, but we don't want to change the buffer for DMA write.

mtk_camsv30_update_buffers_add is called on irq to update the address
to the next buffer (if available).

Maybe the name mtk_camsv30_update_buffers_add is confusing then?
What do you think about:
- mtk_camsv30_update_buffers_add -> mtk_camsv30_update_buffers_address
- mtk_cam_fbc_inc -> mtk_camsv30_buffer_add

Cheers
Julien

 > Regards,
> CK
>
> > +       spin_unlock_irqrestore(&cam->buf_list_lock, flags);
> > +}
> > +
>
> >
>
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