linux-kernel - Re: [PATCH v3 01/15] media: rcar-csi2: Use the pad version of v4l2_get_link

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Message-ID: <20250702205100.GM17819@pendragon.ideasonboard.com>
Date: Wed, 2 Jul 2025 23:51:00 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Niklas Söderlund <niklas.soderlund@...natech.se>
Cc: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: Re: [PATCH v3 01/15] media: rcar-csi2: Use the pad version of
 v4l2_get_link_freq()

On Wed, Jul 02, 2025 at 05:07:11PM +0200, Niklas Söderlund wrote:
> On 2025-06-02 12:43:21 +0300, Laurent Pinchart wrote:
> > On Fri, May 30, 2025 at 04:50:30PM +0300, Tomi Valkeinen wrote:
> > > Use the new version of v4l2_get_link_freq() which supports media_pad as
> > > a parameter.
> > 
> > The commit message should explain why. With that fixed,
> 
> How about this,
> 
> The pad aware version of v4l2_get_link_freq() tries to retrieve the link 

s/pad aware/pad-aware/

> frequency from the media bus configuration using the get_mbus_config 
> operation, and only if the subdevice do not implement this operation 

s/do not/does not/

> fall-back to the old method of getting it using the V4L2_CID_LINK_FREQ 

s/fall-back/falls back/

> or V4L2_CID_PIXEL_RATE control.
> 
> Update the VIN driver to use the pad aware version to be able to support 

s/pad aware/pad-aware/

> subdevices that only provides the link frequency in the media bus 
> configuration. As the implementation falls-back to the old method if the 

s/falls-back/falls back/

> subdevice don't support get_mbus_config, or don't provide a link 

s/don't/doesn't/g

> frequency in the v4l2_mbus_config struct, this is fully backward 
> compatible.

Looks good to me.

As discussed privately, this patch is needed to avoid breakages with the
latest GMSL2/3 drivers posted in [1] on Gen4 platforms. As the patch
makes sense on its own without the rest of the series, I'll take it in
my tree.

[1] lore.kernel.org/linux-media/20250702132104.1537926-1-demonsingur@...il.com

> > Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
> > 
> > > Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
> > > ---
> > >  drivers/media/platform/renesas/rcar-csi2.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/media/platform/renesas/rcar-csi2.c b/drivers/media/platform/renesas/rcar-csi2.c
> > > index 9979de4f6ef1..ddbdde23c122 100644
> > > --- a/drivers/media/platform/renesas/rcar-csi2.c
> > > +++ b/drivers/media/platform/renesas/rcar-csi2.c
> > > @@ -954,6 +954,7 @@ static int rcsi2_set_phypll(struct rcar_csi2 *priv, unsigned int mbps)
> > >  static int rcsi2_calc_mbps(struct rcar_csi2 *priv, unsigned int bpp,
> > >  			   unsigned int lanes)
> > >  {
> > > +	struct media_pad *remote_pad;
> > >  	struct v4l2_subdev *source;
> > >  	s64 freq;
> > >  	u64 mbps;
> > > @@ -962,8 +963,9 @@ static int rcsi2_calc_mbps(struct rcar_csi2 *priv, unsigned int bpp,
> > >  		return -ENODEV;
> > >  
> > >  	source = priv->remote;
> > > +	remote_pad = &source->entity.pads[priv->remote_pad];
> > >  
> > > -	freq = v4l2_get_link_freq(source->ctrl_handler, bpp, 2 * lanes);
> > > +	freq = v4l2_get_link_freq(remote_pad, bpp, 2 * lanes);
> > >  	if (freq < 0) {
> > >  		int ret = (int)freq;
> > >  

-- 
Regards,

Laurent Pinchart