Messages in this thread | | | Date | Thu, 05 Aug 2021 22:05:27 +0200 | From | Paul Cercueil <> | Subject | Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers |
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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.
> 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.
Cheers, -Paul
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