Messages in this thread | | | Date | Fri, 06 Aug 2021 13:01:33 +0200 | From | Paul Cercueil <> | Subject | Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers |
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Hi Greg,
Le ven., août 6 2021 at 12:17:55 +0200, Greg Kroah-Hartman <gregkh@linuxfoundation.org> 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@linuxfoundation.org> 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@crapouillou.net> >> > > --- >> > > 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
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