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

Laurent Pinchart
2022-09-01T18:15:02Z

Hi Paul,

On Thu, Sep 01, 2022 at 05:11:00PM +0200, Paul Kocialkowski wrote:
> On Sat 27 Aug 22, 01:39, Laurent Pinchart wrote:
> > 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@bootlin.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?

I meant that the warning should only be printed of there's an endpoint
connected to the ISP, so I'd first check if the endpoint is present,
return 0 if it isn't, and then check if the ISP driver is enabled and
print a warning if it isn't.

> > > +
> > > + /*
> > > + * 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.
>
> > > + 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