linux-kernel - Re: [PATCH v6 5/6] media: sun6i-csi: Detect the availability of the ISP

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Date:   Thu, 1 Sep 2022 17:11:00 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v6 5/6] media: sun6i-csi: Detect the availability of the
 ISP

Hi Laurent,

On Sat 27 Aug 22, 01:39, Laurent Pinchart wrote:
> Hi Paul,
> 
> Thank you for the patch.

Thanks for the review!

> On Fri, Aug 26, 2022 at 08:41:43PM +0200, Paul Kocialkowski wrote:
> > Add a helper to detect whether the ISP is available and connected
> > and store the indication in a driver-wide variable.
> 
> This sounds like it would be a global variable, while it's stored in the
> driver-specific device structure.

Okay I can clarify the commit message here.

> > 
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > ---
> >  .../platform/sunxi/sun6i-csi/sun6i_csi.c      | 33 +++++++++++++++++++
> >  .../platform/sunxi/sun6i-csi/sun6i_csi.h      |  3 ++
> >  2 files changed, 36 insertions(+)
> > 
> > diff --git a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > index 00521f966cee..b16166cba2ef 100644
> > --- a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > +++ b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > @@ -24,6 +24,35 @@
> >  #include "sun6i_csi_capture.h"
> >  #include "sun6i_csi_reg.h"
> >  
> > +/* ISP */
> > +
> > +static bool sun6i_csi_isp_detect(struct sun6i_csi_device *csi_dev)
> > +{
> > +	struct device *dev = csi_dev->dev;
> > +	struct fwnode_handle *handle = NULL;
> 
> No need to initialize this to NULL.

Indeed.

> > +
> > +	/* ISP is not available if disabled in kernel config. */
> > +	if (!IS_ENABLED(CONFIG_VIDEO_SUN6I_ISP))
> > +		return 0;
> 
> Hmmm... The ISP driver may be disabled when compiling the sun6i-csi
> driver, but later enabled and deployed. Disabling ISP support silently
> like this could be confusing. Could it be better to move this check
> after the graph check, and print a warning message in this case ?

Yeah I'm not too surprised corner cases like this can exist.
Agreed that printing a warning message would be good, but I don't follow the
point of moving the check later on. Do you have something in mind there?

> > +
> > +	/*
> > +	 * ISP is not available if not connected via fwnode graph.
> > +	 * This weill also check that the remote parent node is available.
> 
> s/weill/will/

Good catch, thanks!

> 	 * ISP is not available if not connected via fwnode graph. This will
> 	 * also check that the remote parent node is available.
> 
> > +	 */
> > +	handle = fwnode_graph_get_endpoint_by_id(dev_fwnode(dev),
> > +						 SUN6I_CSI_PORT_ISP, 0,
> > +						 FWNODE_GRAPH_ENDPOINT_NEXT);
> > +	if (!handle)
> > +		return 0;
> > +
> > +	fwnode_handle_put(handle);
> > +
> > +	dev_info(dev, "ISP link is available\n");
> 
> You could make that a debug message, it's not crucial information that
> needs to be printed when the driver is loaded. If you prefer keeping an
> info message, then I'd move it to the probe function and print that the
> CSI has been probed, and indicate in that message if the ISP is
> available.

You're right, let's make this debug. It's more the opposite case that is worth
a warning message.

Thanks,

Paul

> > +	csi_dev->isp_available = true;
> > +
> > +	return 0;
> > +}
> > +
> >  /* Media */
> >  
> >  static const struct media_device_ops sun6i_csi_media_ops = {
> > @@ -290,6 +319,10 @@ static int sun6i_csi_probe(struct platform_device *platform_dev)
> >  	if (ret)
> >  		return ret;
> >  
> > +	ret = sun6i_csi_isp_detect(csi_dev);
> > +	if (ret)
> > +		goto error_resources;
> > +
> >  	ret = sun6i_csi_v4l2_setup(csi_dev);
> >  	if (ret)
> >  		goto error_resources;
> > diff --git a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.h b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.h
> > index e611bdd6e9b2..8e232cd91ebe 100644
> > --- a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.h
> > +++ b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.h
> > @@ -21,6 +21,7 @@
> >  enum sun6i_csi_port {
> >  	SUN6I_CSI_PORT_PARALLEL		= 0,
> >  	SUN6I_CSI_PORT_MIPI_CSI2	= 1,
> > +	SUN6I_CSI_PORT_ISP		= 2,
> >  };
> >  
> >  struct sun6i_csi_buffer {
> > @@ -44,6 +45,8 @@ struct sun6i_csi_device {
> >  	struct clk			*clock_mod;
> >  	struct clk			*clock_ram;
> >  	struct reset_control		*reset;
> > +
> > +	bool				isp_available;
> >  };
> >  
> >  struct sun6i_csi_variant {
> 
> -- 
> Regards,
> 
> Laurent Pinchart

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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