Hi Greg,
Le ven., août 6 2021 at 12:17:55 +0200, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> a écrit :
On Thu, Aug 05, 2021 at 10:05:27PM +0200, Paul Cercueil wrote:
Hi Greg,
Le jeu., août 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> a écrit :
> On Thu, Aug 05, 2021 at 09:21:09PM +0200, Paul Cercueil wrote:
> > When the drivers of remote devices (e.g. HDMI chip) are
disabled in
> > the
> > config, we want the ingenic-drm driver to be able to probe
> > nonetheless
> > with the other devices (e.g. internal LCD panel) that are
enabled.
> >
> > Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> > b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> > index d261f7a03b18..5e1fdbb0ba6b 100644
> > --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> > +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> > @@ -1058,6 +1058,18 @@ static int ingenic_drm_bind(struct
device
> > *dev, bool has_components)
> > for (i = 0; ; i++) {
> > ret = drm_of_find_panel_or_bridge(dev->of_node, 0, i,
&panel,
> > &bridge);
> > if (ret) {
> > + /*
> > + * Workaround for the case where the drivers for the
> > + * remote devices are not enabled. When that happens,
> > + * drm_of_find_panel_or_bridge() returns -EPROBE_DEFER
> > + * endlessly, which prevents the ingenic-drm driver from
> > + * working at all.
> > + */
> > + if (ret == -EPROBE_DEFER) {
> > + ret = driver_deferred_probe_check_state(dev);
> > + if (ret == -ENODEV || ret == -ETIMEDOUT)
> > + continue;
> > + }
>
> So you are mucking around with devices on other busses within this
> driver? What could go wrong? :(
I'm doing the same thing as everybody else. This is the DRM driver,
and
there is a driver for the external HDMI chip which gives us a DRM
bridge
that we can obtain from the device tree.
But then why do you need to call this function that is there for a
bus,
not for a driver.
The documentation disagrees with you :)
And, if that has any weight, this solution was proposed by Rob.
> Please use the existing driver core functionality for this type of
> thing, it is not unique, no need for this function to be called.
I'm not sure you understand what I'm doing here. This driver calls
drm_of_find_panel_or_bridge(), without guarantee that the driver
for the
remote device (connected via DT graph) has been enabled in the
kernel
config. In that case it will always return -EPROBE_DEFER and the
ingenic-drm
driver will never probe.
This patch makes sure that the driver can probe if the HDMI driver
has been
disabled in the kernel config, nothing more.
That should not be an issue as you do not care if the config is
enabled,
you just want to do something in the future if the driver shows up,
right?
Well, the DRM subsystem doesn't really seem to handle hotplug of
hardware. Right now all the drivers for the connected hardware need to
probe before the main DRM driver. So I need to know that a remote
device (connected via DT graph) will never probe.
Give me a of_graph_remote_device_driver_will_never_probe() and I'll use
that.
Much like the device link code, have you looked at that?
I don't see how that would help in any way. The device link code would
allow me to set a dependency between the remote hardware (HDMI chip,
provider) and the LCD controller (consumer), but I already have that
dependency though the DT graph. What I need is a way for the consumer
to continue probing if the provider is not going to probe.
Cheers,
-Paul
